Category Archives: Technical

Electric Car Servicing: A/C and Heating

Electric Car Servicing: A/C and Heating

Air conditioning has become the mainstream on cars since the 1990s, and of course, a car with a premium price tag and showcasing the latest technology can’t be sold without it. Traditionally, a refrigerant compressor is driven by a belt from the engine, and an electromagnetic clutch allows the compressor to be disconnected when the pressure is outside the limits, when full engine power is demanded, or when the driver switches it off. In recent years, this has been replaced by the variable displacement compressor on many cars, which controls the flow of refrigerant similar to a suction control valve on a high pressure diesel pump.

When a hybrid engine stops, there is no way to drive the refrigerant compressor. The first generation Toyota Prius avoided this particular problem by keeping the engine running when the air conditioning was on. This rather inelegant solution was much improved on the second-generation car, by the addition of an electric refrigerant compressor.

An air conditioning compressor draws a similar amount of power to a starter motor, so when running for long periods it’s far more practical and efficient to run this from the high voltage system than attempt a 12V supply. Toyota’s system uses a three-phase motor, powered by an A/C supply from the inverter. There’s no need for a clutch, because of course the car can spin the compressor’s motor at whatever speed it desires.

These days, air conditioning compressors tend to have built-in inverters, so are fed by a fused high voltage DC supply, and internal circuitry operates the motor, typically on a LIN network.

So, what about heating? In the case of a hybrid vehicle, we have the same source of waste heat as traditional cars, so our heating system is largely conventional, save for an electric pump to circulate coolant when the engine is hot but not running.

Electric cars are different, as the big source of waste heat is no longer available. A heating element can be used for cabin heating. In some cases, this is fitted directly in the heater box, similar to a fan heater. It’s more common for the heater unit to be located under the bonnet, and liquid coolant to be pumped around a heater matrix – although slightly less efficient and requiring more parts, this does keep any high voltage wiring out of the interior.

Another solution to cabin heating is to use a heat pump. This uses the existing air conditioning components with a few extra parts (typically a second condenser inside the car, and a few electrical valves) in order to pull heat into the car, rather than pulling it out. The heat is normally sourced from the outside air, sometimes in conjunction with waste heat from power electronics cooling.

Electric heating and cooling gives us numerous other benefits. If you leave at the same time every day, you can set a timer to pre-heat or pre-cool the car ready for you to leave. If the car is plugged in, this power can be drawn from the mains, so not only is your windscreen clear and your car a comfortable temperature, but your battery is still fully charged as well. Some models also use the air conditioning system as part of the battery cooling system, which of course uses further valves to direct refrigerant to the required part of the circuit.

From a servicing point of view, the most important thing to be aware of is the variation of different systems and how it works on the car you’re working on. Even a regas is not as straightforward as it once was – normal air conditioning oil conducts electricity, which doesn’t go down well in an electric compressor, so as well as using the right oil, it’s essential to flush all machine pipework to ensure no contamination. Many models also have specific procedures for regassing to ensure that valves used for battery cooling or heat pumps are in the correct position – if the valves are shut, you may only be regassing part of the system!

Best practice for Timing Belts, Tensioners and Tools

Best practice for Timing Belts, Tensioners and Tools

Gates explains how comebacks and common installation errors are being reduced with a focus on appropriate tools and specific fitting instructions.

In the latest series of Gates technical workshops, the Gates Technical Training and Support Team is providing mechanics around the UK with logical explanations for premature timing belt failures often considered as ‘mysterious’.

Synchronous Belt Drive Systems (SBDS) from two engines with different ‘automatic tensioners’, different belt tension setting procedures and different sets of precision tools have been catching the attention of mechanics on a regular basis.

The engines involved are:

■ Renault 2.2dCi, 2.5dCi engines –2000 onwards

■ Ford 1.8 TD, TDCi, TDDi (all eight-valves)

Technicians sometimes compromise the job by failing to allow engines to return to ambient temperatures. Another common error is to assume that automatic tensioners require no specific tension setting procedures. Without these procedures, automatic tensioners cannot perform effectively and efficiently.

Belt design and construction

Ahead of discussions about the specific installation and belt tension-setting issues, it is worthwhile providing some context by briefly discussing the design and construction of all Gates belts.

The internal ‘s’- and ‘z’-twisted tensile cords contribute not just strength, but also balance and deliver stabilising qualities to the synchronous belt. These combine to help keep the belt centralised on the pulley. Precise belt tension is the key to retaining the central position. It is this that ensures efficient overall performance of the SBDS.

Renault 2.2-2.5 tensioner and setup

Fitted to Renault Espace, Laguna, Master and Traffic models, these engines are also a fixture of some Vauxhall and Nissan ranges. In each case, precise timing belt tension is established through a two-stage process. A Camshaft Locking Tool is required (GAT 4760B) to set the precise tensioner position. With the tool in place, the position is set by means of a lever arm on the locking tool itself. When the lever arm is level with the top of the locking tool, high tension has been achieved.

Note: This is only the desired initial tensioner position.

The Camshaft Locking Tool is then removed and the engine rotated manually, through a specified number of revolutions. The Camshaft Locking Tool is now replaced and the correct installation tension is set by aligning the raised edge of the lever arm. It must be level with the top of the tool. Both stages are essential to the procedure. Completion of both stages is the only way that installation tension can be achieved.

Ford 1.8 TD, TDCi, TDDi (all eight-valves)

Frequently installed on models such as the Ford Galaxy from 2009 and the Ford Mondeo from 2012, advice from the Gates Technical Training and Support Team is that at commencement, the engine must be atambient temperature. Locking and setting tools from the Gates Professional Tools Range (GAT 4830 and GAT 4304) are also recommended for the job.

Vital steps in the fitting procedure include locking the crankshaft and flywheel, locking the camshaft (rear of the engine) and loosening the camshaft sprocket while holding it in place so it’s free to rotate on the taper. This is important because otherwise the top span of the belt cannot be tensioned.

Other important steps include:

■ Rotating tensioner anticlockwise

■ Lining up indicator with the centre of the slot

■ Bolt torque = 50Nm

■ Rotating engine manually (through almost six revolutions)

Re-inserting the crankshaft pin, then rotating the engine to Top Dead Centre completes the automatic tension setting procedure – as long as the indicator remains in the centre of the slot.

Bedding-In Brakes

Bedding-In Brakes

The “bedding-in” for brakes is essential for the brakes to perform optimally and friction is key for efficient braking. Here, Apec explains Bedding-in as well as the Material Transfer Process.


Friction is a force resistant to movement between contacting areas. In braking there are 2 types of friction processes that occur during the material transfer process. To understand the bedding in process and material transfer process, we need to comprehend the difference between the 2 types of friction processes, which are the abrasive and adherent friction process.

Abrasive Friction Process

When the brake pads are compressed against the brake disc, the pressure and contact from the 2 surfaces will generate heat and cause the breaking down of particles on the surface of the material. If you could mount a microscope on a brake pad, you would see tiny particles of the pad and disc breaking away from the surfaces as they contact each other. As this is happening, the heat is physically and chemically changing the exposed friction material as particles are being torn or sheared from both components. This leads to the mechanical wear of the discs and pads, consequently having to be replaced when worn past their limit of performing efficiently. Some particles become part of the friction surface of the disc, while others are cast off and form brake dust, that stick to wheels and eventually will be washed down the drain, potentially polluting the environment.

Adherent Friction (Bedding-in) Process

The particles that become part of the friction surface results in the adherent friction process, which is also known as the bedding in process. This process transfers a layer of brake pad material onto the disc. Once the brake pad material is sufficiently transferred to the surface of the disc, it increases the coefficient of friction or, simply put, makes the brakes more “grabby” to each other. Because there are two forces at work here, adherent friction and pressure, stopping distances can be improved by up to 20%.

The material transferred acts as a sort of adhesive, that literally sticks to the brake pad as it’s being compressed against the disc. This creates a barrier between the pads and the disc preventing the disc from being ground down to a powder by the brake pads and vice versa meaning your brakes will last significantly longer. Adherent friction is not as a destructive force as abrasive friction due to that protective barrier preventing the brakes from being worn down as fast. To ensure continuous smooth operation of brakes, the process of material transfer from the brake pad must be evenly distributed on the disc surface.

Adherent friction is a totally evolving process, as heavy braking will remove some of this material transferred to the disc and will need to be replaced under normal braking conditions.

Recommended Bedding-in Procedure

Bedding-in new discs and pads should be done with care to ensure even material transfer. Correct bedding guarantees that new brake pads and new discs work flawlessly together. During the test drive, the vehicle should be driven at a moderate speed (30-35mph) and brakes should be applied gradually (normally) without coming to a complete stop, to initiate the material transfer process. This process should be repeated for 8-10 times. Avoid more than a minute between each brake application to maintain the temperatures needed for the bed in process. When handing the vehicle back to the customer, it is essential to advise them to brake gradually (normally) and to avoid feathering their brakes or heavy braking for about 200 miles to continue the bedding in process correctly.

Potential Issues

Too little heat during bedding keeps the pad material from transferring to the disc face. Therefore avoid feathering the brake pedal or over-heating the system with heavy braking. This can generate uneven pad deposits due to the material breaking down and sticking to the disc, causing a Stick/Slip situation. Once this has happened, heavy braking will lead to uneven heat build-up due to the uneven distribution of friction material across the disc, with high-spots heating excessively in comparison to the rest of the disc. In the event of this happening this will lead to the disc suffering from excessive Disc Thickness Variation.

Material transfer is a continuous process after bedding in and anything affecting the even transfer of material on the brake disc will cause issues. The biggest cause of uneven material transfer is excessive lateral runout. Please see our article on understanding brake judder for a detailed explanation. Other causes may be as simple as poor technique, using the brake pedal to slow the car rather than engine braking on serious inclines or repeated ‘emergency’ style stops without adequate cooling time or even a mechanical issue such as a sticking pad, slider or caliper that affects the even material transfer process.

Apec focus on quality

All Apec brake pads and manufactured from the latest generation friction materials and benefit from a unique “High Pressure Treatment” (HPT) scorching process to provide superior initial performance and easier bedding in. Apec partially coated discs are made to match OE standards. Just like original discs that have coated hubs and edges, Apec discs have them too! However, there is no coating on friction surface to facilitate the even material transfer process. Without any coating on the friction surface there is nothing to contaminate the pads to reduce their efficiency.

Grease-y Business

Grease-y Business

It is used in all kinds of applications, from bearings and gearboxes to gear wheels and chain systems. It reduces friction, protects against corrosion and seals against water. Then, of course, there’s the unique aspect that it stays in places where oil would simply run off. We are, of course, talking about lubricating grease

The basics of grease

A lubricating grease comprises 80 to 90% base oil, and of course, the choice of oil affects the grease performance. Both mineral and synthetic base oils can be used. The synthetic oils can lend the grease properties that mineral oil can’t, such as a wider temperature range, greater chemical resistance or better electrical properties.

Stays in place

Lubricating grease should provide good lubrication to reduce friction and abrasion and, just like lubricating oils, should also protect against corrosion. However, grease also has unique advantages over oil. It can provide a seal to keep dirt, water and contaminants out of the lubrication point. Grease stays where it is applied, and so can lubricate in areas where an oil would simply run off. This is the reason grease is used to lubricate all kinds of different applications, such as ball, roller and slide bearings, gearboxes and open gear wheels.

Grease or oil?

Because of its consistency, grease stays put in the lubrication point, it has sealing properties, offers good corrosion protection and can withstand heavy loads. However, grease does have some limitations. Unlike oil, grease cannot conduct heat away, for instance in an engine which needs cooling. Nor can lubricating grease be filtered to increase its purity. It’s also difficult to separate water from grease.

Choosing the right grease

Each application places particular demands on the lubricating grease. When choosing the right grease, it is important to consider everything from water, dirt and chemicals to temperature, speed and load. Just as with lubricating oils, the viscosity of the base oil is also important. Low viscosity base oils tend to work better at low temperatures, while lubricating grease with high base-oil viscosity is used with higher loads and temperatures. The speed/revs per minute in the application should also be considered. Low speeds call for a high viscosity base oil, while low viscosity base oils are better in fast-moving applications.

Blend wisely

When a new grease is being used in an application, it is important to know whether the new grease and the old one can be mixed. The best outcome is that no changes are observed, as that means the greases are miscible. The grease mixture may harden, and this can have devastating consequences for a centralised lubrication system. On the other hand, the grease mixture could also soften, which can cause leakage and bearing failure.

Warning: over-lubrication!

It is important to use the right amount of grease, and to lubricate at the correct frequency. More is not always better, and overdosing the grease can be a costly business. Over-lubrication of bearings can lead to higher temperatures and accelerate the oxidation of the grease, which breaks down and ages the grease far more quickly. This can lead to increased wear and eventually component failure.

Seals can also be damaged if bearings are over-lubricated. Too high of a pressure from a grease gun when lubricating bearings can damage the seal, which could enable water and contaminants to get into the bearing, leading to additional wear and corrosion.

To prevent this happening, be sure to review all lubrication points and draw up a maintenance schedule. The schedule will specify the right amount of lubricating grease and re-lubricating intervals.

Safely Replacing TVD Bolts

Safely Replacing TVD Bolts

Trying to decide whether it’s safe to re-use a Torsional Vibration Damper (TVD) bolt is not straightforward. For a start, not all bolts are the same, not all TVDs are mounted in the same way, and they do not all use the same number of bolts. Making the right decision is crucial. Gates offers a helping hand.

A wrong decision could cause a premature drive system failure that will lead to comebacks. In the worst-case scenario, debris from the Accessory Belt Drive System (ABDS) could compromise the timing belt and cause catastrophic engine damage.


TVDs, or damper pulleys, absorb vibrations. Essentially, these vibrations arise from the use of more and more lightweight components to reduce overall vehicle weight and reduce carbon footprints. The additional power from increasingly powerful compact engines creates conflict. Greater power adds strain on lightweight components – causing the vibrations.

The pulleys achieve this thanks to a rubber damping agent, designed to absorb most of the vibrations. That’s one reason why Gates encourages mechanics to install ABDS belt kits that include new TVDs.

The benefits of replacing the TVD at the same time as the belt include:

■ Prevention of failure of the crankshaft by fatigue
■ Decreased wear and tear on the belt, tensioner and other components in the driven assembly
■ Improvement in noise, vibration and harshness (NVH) characteristics. This increases the level of comfort for drivers and their passengers

Installing a TVD correctly protects all the components in the drive system and extends their operational lifetimes.

Complex decision

TVDs are ‘secured’ or ‘fixed’ in one of four alternative ways. These may involve:

  • A single central crankshaft bolt
  • Multiple crankshaft bolts
  • Multiple installation bolts
  • A combination of crankshaft bolts and installation bolts

There are additional complications to consider. For example, bolts that encounter elastic, temporary deformation during fixation can be re-used. This is because they regain their original form after the stress is relieved. Bolts that encounter plastic, permanent deformation during the installation of the TVD, cannot be used to install a new damper, as they might break. Moreover, some TVD bolts always require replacement. Others can be re-used without any issues. If there is more than one bolt, the crucial decision is multiplied.

Easy solution

Replacing all the bolts all the time is one solution, but throwing away a good re- useable bolt negates some of the vehicle manufacturer’s initial efforts to reduce the overall environmental impact. The sensible solution is to always replace the bolts that must always be replaced. Recycling re- usable bolts safely saves resources and respects the environment.

Gates has updated its entire DriveAlign TVD range. Each red Gates box includes the TVD and just the bolts that must always be replaced. In other words, as an installer, you get everything required to complete the job with premium parts, technical clarity and peace of mind. It’s an environmentally respectful job well done – every time.

Old School Diagnosis: Suzuki Vitara

Old School Diagnosis: Suzuki Vitara

Josh Jones had his hands full with an old- school Suzuki Vitara this month. Here, he recalls how refreshing it was to work ‘scan tool-free’ and go back to basics.

I have had a few blasts from the past this month – it really does feel like I have traveled back 15 years to my apprenticeship, and its been fun. In between working on a car fitted with actual K-Jetronic mechanical injection (I appreciate some people reading this now won’t even know what that is, which makes me feel very old indeed) and another fitted with a real life distributor, was a 1998 Suzuki Vitara with a 1.6L G16B engine fitted. This vehicle had been passed to a local garage with a non-start issue and unfortunately they had drawn a blank on the cause, so I was asked to take a look. I welcome the chance to work scan tool-free, and as the vehicle was built before the start of the current millennium, I do not possess a serial communication tool compatible with this vehicle!

The thing I love about this particular type of car is the accessibility of pretty much any component, making it easy to test. Most of us are now used to unobtrusive testing. Gaining access to specific components can be a seriously time consuming process if, in the end, no positive result comes from the graft.

On the Suzuki, however, it was kind of like working on a training rig. For instance, simply look under the dashboard and there is the ECU, held in place by only two 10mm bolts – lovely. Upon cranking, the engine was not noisy and did not display any signs of mechanical fault. So, with my trusty DVOM and scope, I set to work.

Believe it or not, the engine was fitted with single point injection and with the injector harness itself being clear to see and test, I decided the easiest starting point would be to check voltages to establish if the engine ECM was at least powering up, i also wanted to check if the engine’s rotation was being picked up correctly by the crank sensor, and thus initiating fuelling and ignition. The injector was easy to separate as there were simply two wires emerging from the centre of the throttle housing and they were linked to the main wiring loom via a connector. I connected here with a power probe to check operation on cranking, but got absolutely nothing – no ignition supply or switching signal on either wire. Was the ECM even powering up? Upon cycling the ignition switch, I listened for a fuel pump prime and could hear one for definite. In light of this, I was sure the control unit was at least coming to life when the key was turned on.

To check if the spark ignition side of things was operational, I carried out a simple test using the same two wires, in order to save time. With the fuel injector disconnected at the aforementioned plug, I manually activated it with the power probe for a very short period. The injector could be heard to click and the holding pressure in the fuel system from previous ignition cycles delivered a very small amount of fuel into the inlet manifold. I then simply cranked the engine, which straight away coughed into life – briefly – before obviously dying again. I was confident I was looking at a lack of fuel injection as the cause of the non-start condition.

According to a wiring diagram of this particular engine management system, the fuel injector is not only controlled by the ECM but is also electrically driven by it directly, as opposed to the power source coming from a control relay as per most multipoint systems. My next task was to evaluate the integrity of the connections between the injector and ECM, but this is where things got a bit strange for a moment. With the ignition switch turned off and with the injector disconnected at the same multi- plug, I carried out a continuity test from the injector control terminal on the ECU side of the plug and battery negative, simply to check whether or not there was an open circuit. When the ignition was turned on, the test showed an open circuit. When the ignition was turned back off, about five seconds would elapse before the ground path would return, presumably via the ECM. It was at this point that a little nagging thought from earlier came back into my head. Up until this point, I had not paid much attention to the fact that there had been no sign of a ‘check engine’ warning lamp displayed, even in a ‘key on, engine off mode’, which is why I needed to use the fuel pump prime as a rudimentary way of confirming ECM power up.

On a newer model, no EML would have rung alarm bells straight away, but as this vehicle was pre EOBD, I simply did not pay enough attention to the missing lamp. Upon closer inspection of the instrument cluster, I found that there was a poor connection on the PCB. This turned out to be the ‘check engine’ lamp, which was trying its best to frantically flash at me every time the key was turned on, but could not due to the loose bulb. A check of the owner’s manual (which was still present, amazingly) confirmed my suspicion – a flashing lamp was a warning that the key transponder was not recognised!

After this discovery, I wanted to confirm that it was indeed the key transponder itself at fault and not any wiring or immobiliser module issues, as this could have potentially made the vehicle uneconomical to repair. I used my amps probe (see above) to connect to the receiver ring circuit of the immobiliser. When the key was cycled to the ignition position, the immobiliser control unit attempted to probe for a response from the key chip before giving up (see below).

Carrying out the diagnosis this way allowed me to understand the functionality of the factory immobiliser system. It certainly explained the open ECM injector circuit; when the ignition was cycled, the immobiliser obviously isolated it and the key was not being recognised. It was also interesting to note that spark ignition was still operating, even though the fuel system was disabled upon the security system becoming active.

After a call to my friendly local locksmith, it was confirmed that a new transponder was very easy to program. After his visit, I checked to see that – with the current probe – the key was once again responding correctly. You could clearly see a difference – only one ‘pulse’ was needed to communicate before the chip was energised to respond. The rhino was ready to roam the plains once more. Lesson learned!

ABS Sensors: Troubleshooting and Replacement

ABS Sensors: Troubleshooting and Replacement

Braking components have continued to evolve over the past few decades, from drum and disc brakes to copper-free pads and disc coatings. Now, the addition of advanced electronic controls has enabled braking systems to become even safer and smarter than ever before.

As vehicles become better connected, technologies such as anti-lock brakes (ABS), electronic stability and brake assist are becoming commonplace. These advancements are just a selection of what technicians must keep up to date with, and companies are well positioned to provide the components and technical advice that workshop professionals need to service these increasingly complex vehicles.

Failing ABS sensors

Given its position within the ABS system near the road surface and associated debris, the reluctor wheel or tone ring can easily become dirty or damaged – as can the sensor.

This can result in weak or complete signal failure from the sensor. Other common causes of failure include breaks in wiring, sensor winding due to excessive vibration, or increased wheel bearing clearance.

A faulty ABS sensor can impact several important braking functions and could exhibit the following warning signs:

ABS warning light: normally the first sign that there’s a problem with the system – this could be caused by either a sensor or control module fault. Once the ABS light has illuminated, the ABS system is automatically disabled and will not override manual braking.

Traction control light: since the ABS sensor also feeds data to the traction control system, issues could illuminate this light, too.

Reduced stopping power under heavy braking: the vehicle may take longer to stop or experience a loss of traction and control when braking heavily.

Less stability under wet or icy conditions: drivers may experience reduced traction and tyre slippage when driving on wet or icy roads.

Troubleshooting an ABS sensor

To identify the source of any sensor faults, we suggest connecting a diagnostic tool to record the fault codes and check the live data. This process usually disables the ABS system. Using a multimeter and oscilloscope to check the supply voltages and signals, taking a measurement to test the line between control unit and sensor.

Next, inspect the sensor’s connectors and wiring to ensure they are correctly positioned, looking for signs of damage or contamination. Now do the same for the sensor and impulse ring. If at any stage components are contaminated, clean the contact surface using a wire brush.

How to replace a faulty ABS sensor

Once an ABS sensor fault has been identified, we advise following these simple best practice sensor replacement steps:

  • Loosen the wheel nuts before jacking the car up (do not remove wheel nuts yet). Consult the owner’s manual for correct jacking points and ensure that the vehicle is raised and supported securely
  • Remove the wheels and move aside to access the brake system. (You may also need to remove the brake pads and discs). Once accessible, remove the bolt that holds the sensor onto the hub and the clips that secure the sensor wiring to the vehicle’s chassis/body
  • Unplug the sensor
  • Clean the area around the sensor with an emery cloth
  • Working in reverse order, now install the replacement ABS sensor. Start by plugging in the sensor and then routing the harness back so it is secured to the body/chassis, then insert it into the hub
  • If you had to remove the pads and discs, reinstall them and torque to the correct specifications
  • Refit the wheels, tighten and lower the vehicle to the ground
  • Torque tighten the wheels to the manufacturer’s specification
  • Reconnect the diagnostic tool and dismiss any fault code(s). Run the engine and check for any new faults. If no faults display, exit the diagnostic software and switch off the ignition
  • Finally, check that the ABS warning light has gone out and carry out a road test

Diagnosing a Failed Lambda Sensor

Diagnosing a Failed Lambda Sensor

First fitted to passenger cars in the 1970s to improve the engine’s combustion efficiency and reduce exhaust emissions, the lambda sensor is now a key component within the engine management system. But what are the visual symptoms of failure?

In order to operate efficiently, an internal combustion engine requires the correct ratio of air and fuel in its cylinders during the combustion process, with the ideal – known as lambda – being 14.7 parts air to one part fuel for a petrol engine and 14.5:1 for a diesel. Lambda sensors operate by measuring the amount of oxygen in the exhaust, to allow the engine management system to make the necessary adjustments to remain as close as possible to the ideal ratio.

These measurements have now become so precise that many vehicles feature several lambda sensors situated in the exhaust system, both before and after the catalytic converter. As global emissions standards have become ever more stringent, the variety and complexity of lambda sensors has increased accordingly and now includes zirconia, titanium, planar and wideband.

Causes of failure

The lifespan tends to be 45,000 miles for an unheated sensor, whereas a heated sensor can typically last closer to 100,000 miles, so many will simply fail due to age. However, vibration or damage to the heater element, connectors and/or wires could be a cause of premature failure. Other less obvious reasons can be identified by examining the visual appearance of the failed sensor.

A guide to visual symptoms and possible causes


Visual signs – The sensor nose will have a grainy white/light grey coating.

The cause – Coolant with anti-freeze may have affected the combustion process and reached the lambda sensor.

The solution – Check the head gasket for leaks and repair if required.


Visual signs – The sensor nose will be contaminated with white or red deposits.

The cause – Excessive use of an engine or fuel additive can contaminate or block the lambda sensor.

The solution – Cleaning the fuel system prior to replacement.


Visual signs – Oily black deposits left on the sensor nose.

The cause – The vehicle may be burning excessive oil.

The solution – Prior to sensor replacement, thoroughly check the engine for leaks, including the usual seals that are prone to failure.


Visual signs – Black soot on the sensor nose.

The cause – A damaged sensor or fault in the fuel system can result in a high air to fuel ratio, producing black soot.

The solution – Measure exhaust gases to ensure the fuel system is working. Check the sensor heater control and sensor heater.


Visual signs – The sensor nose is contaminated with shiny grey deposits.

The cause – Now far less common, but usually caused by leaded fuel attacking platinum parts or the sensor.

The solution – Replace any leaded fuel in the system before fitting the replacement sensor.

How to: Replace the Clutch on an Audi A1

How to: Replace the Clutch on an Audi A1

This month, the resident expert Alistair Mason replaced the clutch on a 2016 Audi A1, fitted with a 1.6L TDI engine that had covered more than 85,000 miles.

Audi launched the A1 into the UK market back in November 2010, and sales have reached close to 200,000. It is built on Volkswagen’s PQ25 platform, which is also used for the Volkswagen Polo and Seat Ibiza.

Being Audi’s popular Supermini, with a repair time of just five hours and a requirement for only minimal workshop equipment – a two-post vehicle lift, engine support, transmission jack, clutch alignment tool and locking wheel bolt key – this repair is a good one for an independent workshop.

Step-by-step procedure

First, place the vehicle on the lift, open the bonnet and boot, and disconnect the negative lead (see below) from the battery in the boot well, but do not close the boot whilst the battery is disconnected. Before proceeding to the engine bay, slacken the front locking wheel bolts and both front hub nuts.

In the engine bay, remove the plastic engine cover and air box assembly (see below), then disconnect the battery connection to the air box carrier, and then remove the carrier itself. That provides good access to the top of the gearbox and bell housing area.

Disconnect the gear change cables, and remove the clutch slave cylinder, leaving the hydraulic pipe connected. Detach the starter motor cable and unscrew the top starter motor bolt, before disconnecting the reverse light switch multiplug and removing the top bell housing bolts.

Next, raise the vehicle lift to gain access to the underside and slacken the inner driveshaft joint bolts, then lower the lift to waist height and remove the front wheels and hub nuts. In addition, remove the N/S plastic wheel arch liner to give better access to the gearbox.

Raise the vehicle lift once more and unscrew both bottom ball joints. The outer driveshaft joints can then be detached from the hub assemblies by pushing the hub assemblies outwards, before undoing the inner driveshaft joint bolts, removing the heat shield for the O/S driveshaft and driveshafts themselves.

To aid the removal of the gearbox, it is best practice to remove the O/S driveshaft flange from the gearbox that is retained with an Allen bolt in the centre of the flange (see below).

Once removed, unscrew the lower starter motor bolt, remove the starter motor and disconnect the gear recognition multiplug (see below).

Next, detach the lower bell housing bolts, leaving two easily accessible bolts to support the gearbox, before removing the bottom pendulum gearbox mount. Alistair used two transmission jacks to support the engine and gearbox respectively, before using a ladder to gain access to the engine bay and remove the gearbox mounting bolts.

Now, lower the gearbox and engine slightly, removing the gearbox mounting from the gearbox accessed from the N/S wheel arch (see below). Finally, undo the last of the bell housing bolts and ease the gearbox away from the engine. Once clear, lower the transmission jack holding the gearbox and move it to a safe area.

Clutch replacement

Remove the clutch assembly from the flywheel and inspect the back of the engine for any leaks, rectifying if required. Clean the back of the engine and flywheel with brake and clutch dust cleaner, and as a solid flywheel is fitted, remove the glaze from the flywheel face using an Emory cloth and clean again with brake and clutch dust cleaner.

Remove the release bearing from the gearbox and the release arm, closely inspect it for any wear, along with pivot point and release bearing guide tube (see below), replacing if required, and clean the bell housing area with brake and clutch dust cleaner.

Fit the release arm and bearing. If plastic/nylon runs on metal, no lubrication is required; if metal runs on metal, lubrication is required and a light smear of high melting point grease is best practice.

Apply another light smear of high melting point grease to the gearbox input shaft splines, before mounting the new clutch plate onto them. This will confirm the clutch plate is the correct fit, and it will also evenly distribute the lubrication on the input shaft. Remove the clutch plate and wipe any excess grease.

Ensure the clutch plate faces the correct component (see below), and using a universal clutch alignment tool, align it with the clutch pressure plate and secure.

Mount the clutch assembly onto the flywheel (see below), before inserting, tightening and torquing all clutch bolts evenly and sequentially. Once torqued, remove the clutch alignment tool.

Before refitting the gearbox, ensure all wiring etc. is clear of the bell housing area, so as not to get trapped, while also checking the gearbox alignment dowels are fitted to the engine and that the release mechanism in the gearbox is fitted and functioning correctly.

Gearbox replacement

Place the gearbox on the transmission jack, bring it close to the engine and ease into position, ensuring it locates on the alignment dowels. When in position, fit two easily- accessible bell housing bolts and tighten, refit all other components in reverse order of removal and torque all bolts to the manufacturer’s specification. After the battery lead has been reconnected, reset all electrical consumers.

It is worth nothing that new hub nuts will be required, if the locking tabs break off during removal. Finally, as always, carry out a road test to ensure a quality repair.

Snowblind: Essential Checks for your Car for the Coming Months

Snowblind: Essential Checks for your Car for the Coming Months

You may think that we’re being premature, but it’s better to think ahead now and prepare than to be caught out down the line. These are our recommended checks for your car for the colder season.

The aim of any winter check is to increase driver safety and to ensure that the vehicle is well protected against the cold, rain,frost, and other seasonal elements. Below is a handy list of the key checks that technicians should carry out when a vehicle rolls into the workshop for a winter service.

The right tyres

The first step should always be to check the tyres. Is the tread depth sufficient and are they free of damage? These factors are key in ensuring that the vehicle does not skid under braking or start to aquaplane dangerously if the driver encounters black ice, rain or slush on the roads. Like in most European countries, a minimum tread depth of 1.6mm is prescribed in the UK. However, this should be considered the bare minimum.

The aim of any winter check is to increase driver safety and to ensure that the vehicle is well protected against the cold, rain,frost, and other seasonal elements. Below is a handy list of the key checks that technicians should carry out when a vehicle rolls into the workshop for a winter service, as well as details of just some of the components available from Herth+Buss, which can help give added peace of mind.

The right tyres

The first step should always be to check the tyres. Is the tread depth sufficient and are they free of damage? These factors are key in ensuring that the vehicle does not skid under braking or start to aquaplane dangerously if the driver encounters black ice, rain or slush on the roads. Like in most European countries, a minimum tread depth of 1.6mm is prescribed in the UK. However, this should be considered the bare minimum.

The tyre pressure also plays an important role. Ever since November 2014, a tyre pressure monitoring system has been required on all new cars for safety reasons. In this system, sensors check the tyre pressure and notify the driver if the pressure drops. Faulty sensors can easily be replaced.


The lighting fixtures on the vehicle obviously play an essential role in winter. Darkness, rain, snow and fog all reduce visibility, as do mud and dirt thrown up from the road. Headlights can lose up to 60% of their luminosity after just half an hour of driving on dirty roads. In addition to ensuring that all lights are fully functional, you also need to check that the headlights have been correctly adjusted. If they have been set too high or too low, oncoming drivers will be dazzled.

If a light on one side of the vehicle is faulty, it is always recommended to replace the light on the other side too, so as to stop that light failing as well. This is because the two lights usually have a similar service life. In contrast, moisture on the inside of headlights does not pose a problem. It manifests itself as a thin layer inside the lens. It is produced when cold outside air meets the heat produced by the headlights, and generally disappears when the headlights are switched on.
However, if there is a relatively large quantity of water inside the headlights, it is recommended to replace them. In many European countries, it is now also compulsory to switch on the headlights during the day. Special daytime running lights are ideally suited to this task. They are used in addition to the headlights, but are weaker, use less power and last longer.

Windscreen and rear window

When it comes to ensuring that drivers have a clear view, the windows are just as important as the lights. As any drives can attest to, if the windows are iced up, it is easier to clear the ice from a clean windscreen or rear window than a dirty one. To ensure drivers have a clear view even when the temperature drops below freezing, the windscreen washer system also needs to be filled with a suitable antifreeze agent. So- called nano-seals can also be used to help rainwater run off the vehicle. If your customers keep a sharp ice scraper in their glove box, please note that it will damage the glass. Recommend to your customer that they use a plastic scraper which is kinder to the glass!

Body and suspension

Road salt is used by city and municipal authorities to stop ice forming on roads. According to new findings, it is less harmful to modern paints than was generally assumed to be the case. Salt only becomes a problem if it rubs against the vehicle and causes scratches, which then allow the ingress of moisture. Customers should be informed about such paintwork damage as there is a risk that rust will form here, and treating rust can be expensive. Another important way of stopping rust forming is to clear leaves from corners and nooks/crannies to ensure that water can drain away correctly and exhaust- air ducts are clear. You should also check, clean and, if necessary, seal the underbody.

Suspension parts such as the axles, joints and hinges are at much greater risk of suffering from rust. Unlike the sheet metal for the body, these components are not galvanised and are therefore particularly susceptible to rust. Rust can be prevented using greases and penetrating oils from spray cans. However, this protection needs to be reapplied regularly as it is rinsed off by water over time as the vehicle is being driven.


The battery is by far the most common cause of breakdowns in winter. It is placed under high loads as the heating and lighting systems on the vehicle are constantly in use. Modern maintenance-free batteries generally no longer require a great deal of time and attention. However, you should ensure that they are not discharged completely as this usually means they fail.

When removing batteries, always remove the negative cable first and then the positive cable (follow the reverse order when installing batteries). To charge batteries using a charger, the correct voltage first needs to be set on the device. If the batteries are not maintenance-free, the technician needs to cast their well-trained eyes over the ‘magic eye’, which indicates the battery’s state of charge and acid level. Fluid may, of course, need to be topped up and the battery charged.

A battery tester is recommended for this. Additionally, you could recommend a jumper cable to your customers if they do not have one yet. Powerful assisted start devices and chargers should form part of the basic equipment in any workshop, particularly in the cold winter months.


Here, it is important to ensure that the coolant contains enough antifreeze agent. If the engine’s water circuit freezes, it can cause expensive damage. The best way to check whether there is enough antifreeze agent is to use a cooling spindle. Please note that not every antifreeze agent is suitable for use in every radiator. Therefore, always carefully read the respective manufacturer specifications before using the product.

Air filter

In winter, the interior air filter is in heavy demand as the windows frequently fog up. If the filter is clogged, less air will flow through the filter and the windows will fog up faster. Therefore clean and, if necessary, replace the filter.


When the roads are wet and slippery, drivers need to be able to rely fully on their brakes. As such, it is crucial to test them to ensure they are working properly. You should set great store in using high-quality products because the brakes – as a safety-critical component – leave no room for errors, particularly in winter.

It is crucial to regularly check and, if necessary, clean all components in the brake system, particularly in winter. From the brake cable to the pads, pay careful attention here to ensure everything is in perfect condition.

Control system and shock absorption

The aspects to bear in mind for the brakes apply in equal measure to the control and shock absorption systems. After all, the roads themselves are also affected by the weather. Minor damage may become worse in winter due to the higher loads, causing a domino effect. If the shock absorbers are affected, the handling will be significantly impaired. Rubber parts designed to mitigate the friction from metal parts become brittle due to the moisture, and therefore fail. As such, it is important to take action promptly if required, by replacing damaged or faulty parts. When doing so, only use parts of OE quality or a comparable quality level.

Diesel fuel filter

Owners of diesel vehicles need to take particular care in winter because the fuel gels at low temperatures and clogs the fuel filter. In the worst-case scenario, the engine stops receiving fuel and stops working. In the winter months, this is why petrol stations offer winter diesel, which is less susceptible to this problem. If winter diesel is not available or a significant drop in temperature is imminent, additives can offer additional peace of mind. They are added to the tank and ensure that the diesel remains in a fluid state down to temperatures of –31°C.

Ensuring total customer satisfaction

As a specialist, the most important advice that you can offer your customers in winter is to ensure their vehicles are regularly maintained. If you look after your vehicle all year round, there will be no nasty surprises come the winter months and you will ultimately save money. Similar advice applies to spare parts: If something needs to be replaced, we strongly recommend opting for a part manufactured to OE or a comparable quality level. Although it might cost a little more, this investment will pay off and the benefits will be clear to see when it comes to performance, durability and maintenance.