Category Archives: BMW

How to change a clutch on a BMW 3 Series

The 3 series is the best selling model in BMW’s range, representing nearly 30% of sales for BMW. A clutch replacement on this model is really straight forward and, with the guidance of the LuK ‘Clutch Clinic’, the whole process will become even easier.

Launched in 1975 the BMW 3 series has seen many updates over the years, winning lots of awards along its journey. A compact executive car, its popularity is unlikely to diminish, meaning the likelihood of one arriving at your garage will remain pretty high.

We used a two-post ramp in this article, however a four-post ramp would also be suitable. A transmission jack, a long axle stand and a special alignment tool is also required.

Disconnect the battery earth lead and raise the vehicle. Unbolt and remove the plastic under-tray which will expose an alloy plate that should also be removed. Remove the front section which exposes the exhaust bracket that is bolted to the gearbox; this can be removed later as it is fixed with three bell housing bolts. Support the rear exhaust silencer and unbolt the two supporting brackets. Split the rear section of the exhaust from the front section and carefully lower out of the way to gain access to the heat shield. Unbolt and remove the heat shield to expose the propshaft.

Remove the crossmember support for the gearbox

Support the gearbox using the long axle stand and remove the cross member support for the gearbox.

How to change a clutch on a BMW 3 Series

You may need to carefully bend the heat shield out of the way to allow better access to the bolts. Unbolt and remove the slave cylinder and stow to one side. Unclip the reverse light switch on the side of the gearbox.

How to change a clutch on a BMW 3 Series

Remove the bolts holding the propshaft centre bearing then mark the propshaft position and remove the bolts holding the propshaft to the gearbox. Carefully swing the propshaft to the side and secure out of the way using bungee ties. This allows plenty of room to remove and lower the gearbox.

The exhaust bracket from earlier can now be removed, along with the three bell housing bolts. Disconnect the gear mechanism by removing two pins – they are held by two metal tabs that are prised upwards.

How to change a clutch on a BMW 3 Series

Remove the clip from the gear mechanism to the gear lever and tap it off, however be careful not to lose the two small nylon shims either side of the link arm.

How to change a clutch on a BMW 3 Series

Remove the 10mm bolt from the gearbox closing plate and remove the remaining bell housing bolts – the two top bolts are a little tricky. Knock the starter motor dowel through the bell housing using a punch to release the starter motor. Once the bell housing bolts are removed, carefully lower the gearbox to the floor. Remove the worn clutch, bearing and fork. It is important to remove the worn fork pivot and replace it.

How to change a clutch on a BMW 3 Series

In this example the dual mass flywheel (DMF) was also replaced with the clutch and bearing, however, in most cases you have no need to replace the DMF as this can be checked whilst on the vehicle for signs of heat stress and evidence of grease loss. The DMF should also be tested for free play and rock between the primary and secondary masses. LuK tool number 400008010 is specifically designed for this purpose and full instructions and DMF tolerances can be found by searching “DMF data sheet” at

Clean the first motion shaft splines and any debris from the bell housing (especially important when a release bearing has failed). Put a small dab of high melting point grease (not a copper-based product) on the first motion shaft splines and make sure the new driven plate slides freely back and forth. This not only spreads the grease evenly but also makes sure you have the correct kit. Wipe any excess grease off the shaft and driven plate hub.

Fitting the new clutch
Fitting of the new clutch will require a special tool. The clutch is a self-adjusting clutch type and it is also fitted with a transit locking plate between the wear cradle and diaphragm springs. Note: do not remove this locking plate until the clutch is bolted to the flywheel.

How to change a clutch on a BMW 3 Series

After checking the spigot bearing check the adjusting springs on the new clutch pressure plate to make sure they are fully compressed. Fit the clutch alignment tool and locate it into the spigot bearing on the flywheel. Place the driven plate over the alignment tool, making sure the correct side is facing the gearbox (note: ‘Getriebeseite’ means ‘gearbox side’ in German).

How to change a clutch on a BMW 3 Series

Bolt on the pressure plate, tightening each opposing bolt progressively around the cover until the desired torque setting is reached. Once the driven plate is secured the locking plate can now be removed. To remove this use an appropriate sized Allen key in the centre of the plate and rotate it anticlockwise – this can be discarded once it has been removed. Finally remove the alignment tool by using an appropriate size bolt. Refitting is the reverse of removal.

How do Stop-Start systems work?

The last few years have seen the introduction of Stop-Start systems by many manufacturers across various vehicle models to improve fuel consumption and reduce exhaust emissions.

One of the main problems the introduction of Stop-Start systems has caused is that when the starter is operated the voltage in the vehicle’s electrical system can drop. In normal circumstances this is not a problem, the vehicle is not usually in “driving mode” and it doesn’t matter if some of the vehicle electrical systems do not function during starter motor operation (exterior lights, heating & air conditioning and audio systems, for example). However, during driving this is not acceptable for reasons of safety and driver convenience.

To counter this problem most systems use an additional power supply to ensure that voltage-critical equipment will not stop operating during starter motor operation. For some models this consists of a large capacitor that is charged by the alternator using engine power, or kinetic energy generated during deceleration and braking.

Considerable thought has been given to the safety mechanisms; most, if not all, Stop-Start systems will not operate if any of the doors or the bonnet is open and will only operate if sufficient vacuum is available to ensure the normal operation of the braking system.
As the use of Stop-Start technology is increasingly adopted, there are now as many systems as there are manufacturers, but they can be categorised as follows:

  • Those using a “conventional” starter motor
  • Those using a combined starter motor/alternator

Although some models use a conventional starter motor for cold start and Stop-Start operation, it is usually modified to ensure it can withstand the extra use it will encounter. However, the time taken to start the engine with this system is thought by some to be too long so other models are using a different approach.
Battery technology is also changing, with the extra starting cycles requiring a more robust battery construction. Absorbent glass matt (AGM) batteries, Gel batteries or the slightly cheaper enhanced flooded batteries (EFB) variants can be found in most vehicles with Stop-Start systems. Replacement of these batteries may necessitate programming of the vehicle’s computer system to allow the battery degradation process to be monitored. On many models the Stop-Start system will be disabled for up to 24 hours following battery disconnection or replacement to allow the battery condition to be evaluated.

Which Stop-Start Application Do They Use?
Toyota Yaris

The Stop-Start system of the Toyota Yaris has its starter motor in constant engagement with the flywheel ring gear and then the ring gear is connected to the engine flywheel with a one way clutch. This, together with recognition of the engine’s static crankshaft position, allows instantaneous ignition of the correct cylinder, thereby reducing starting time.

It is interesting to note that the number of starter motor operations is recorded and the calculated “end of starter lifespan” is indicated by a flashing warning lamp on the instrument panel. After replacement of the starter motor the counter has to be reset.

PSA group

Using a conventional type of starter motor for cold start, the Peugeot/Citroen group employs a combined starter motor and alternator assembly (so called reversible alternator) for the Stop-Start system. Connected to the engine crankshaft with the auxiliary drive belt, it provides silent operation and short starting time.

Unlike conventional alternators, diodes are not used; instead voltage rectification and motor operation use metal–oxide–semiconductor field-effect transistors (MOSFETs). Presently, it would appear that it is only the “e-HDi” models that use the aforementioned capacitor.

3 Essential Items That You’ll Need When Servicing Stop-Start Systems

Starters & Alternators 

Used in many modern vehicles, StARS (Stop start Alternator Reversible System) consists of a reversible alternator that replaces the conventional alternator and starter motor. The reversible alternator provides the function of alternator and starter combined with the new design allowing the conversion of electrical energy into mechanical energy, and visa-versa.

StARS works similar to the conventional alternator where the later applications would have the charge rate controlled by the vehicle ECU (computer controlled and smart charge systems). The new variation now has a separate ECU which administers the reversible alternator and the vehicle’s engine.
When the vehicle is slowed down by the user the ECU analyses the speed of the car and if/when the speed falls under 5mph the ECU switches off the engine. Once the brake pedal is released the ECU then gives an order to start the engine again. The reversible alternator plays the part of the starter motor to achieve this.

The system is designed to work in 5 phases:
1. The vehicle is switched on and the ECU will crank/start the engine. This is achieved by the battery providing electrical energy and the reversible alternator then acts as a starter motor to help crank the engine.

2. During normal driving (when the vehicle is not being slowed down) the reversible alternator then acts as a conventional alternator by converting the mechanical energy into electrical energy and charging the battery.

3. Once the vehicle speed has been reduced below 5mph by braking the StARS ECU gives a command to stop the engine.

4. Once the brake pedal has been released the StARS ECU then gives a command to start the engine again. The battery provides electrical energy and the reversible alternator plays the part of the starter motor and cranks the engine.

5. The vehicle is switched off and the ECU will stop the engine

AUTOELECTRO provides a whole array of replacement starter motors and alternators for modern Stop-Start systems and applications.

Servicing Data 

AUTODATA has enhanced its online product offering to include technical information on vehicles with Stop-Start technology.
The technical information provided by Autodata on its online system enables technicians to identify the specific location of key elements such as the main battery, additional battery and the Stop-Start capacitor.

Procedures for disconnecting and reconnecting each element are clearly explained along with additional information for servicing the system.

Replacement Batteries
EXIDE has expanded its coverage of the UK car parc with new AGM and ECM batteries. The new products cover vehicles from VW, Audi, Toyota, Ford and a slew of other brands.
Exide’s AGM batteries are claimed to have around three times the lifecycle durability of standard batteries. Parts of “matching quality”, they are designed for cars with Start-Stop and regenerative braking systems. They are also used in standard vehicles to increase endurance and performance.

AGM battery coverage: Audi A1, A4, A5 and Q5; BMW 5, 6, 7, X5 and X6; VW Golf, Polo and Touareg; Chrysler Voyager; Dodge Caliber; Jeep Cherokee and many others.

ECM battery coverage: Ford Fiesta, Galaxy, Focus, Mondeo, B-Max, C-Max and S-Max; Toyota iQ; Mazda CX-5 and a range of other models.

Diagnostic Troubleshooting – the pitfalls of ‘diagnosis by fault code’

Recently we had a visit from a Peugeot 206 that arrived at the workshop with a stallingcomplaint. The owner explainedthat when she came to a halt on a roundabout or in stationary traffic, after 10 seconds or so the engine would start running ‘lumpy’ and then cut out. The car had been taken to a number of garages where various parts had been changed but the problem still existed.

The Peugeot engine

First things first, I took a look under the bonnet and all seemed to be in order so it was time to take the car out on the road. I didn’t have to wait too long to notice the problem myself, however after coming to a halt the car restarted straight away. In order to investigate further I decided to take the car on an extended test drive to see if its performance was affected in any other way. Although the car did perform well it was slightly sluggish at the top end so I made sure to double check that the cutting-out was still occurring before taking the car into my workshop to have a proper look.

Back in the workshop

Using the scan tool first, no DTCs were logged. I then checked the serial data and, again, all appeared to be as it should. The 206 is a car I see on a regular basis, mainly for reboot maintenance, so at this point I decided to look at the basics in a little more depth. The air filter and air intake pipes were checked, and despite their clean appearance, the air filter looked like it needed replacing. The car stalled whilst in my workshop and appeared to be running ‘lumpyish’ before cutting out.

The fuel pressure test

With scope in hand my attention was now drawn to the 12 volt power supply coming from a multi-purpose relay which is mounted under the ECU. Removing the ECU usually uncovers a damp and dirt trap; this is exactly what I found so needless to say there was a bit of cleaning required. After disconnecting the relay, checking the pins and cleaning the sockets the connection was sound and the 12 volt supply was all in working order. I then restarted the engine, allowing it to run, but once again the engine began to sound lumpy and cut out. This was strange but I could now tell that the engine did not have an electrical supply problem. The earth path was checked for possible high resistance (which can cause running problems) but there were no troubles there either.

It was now time to move on to the idle air control valve, throttle position sensor, the map sensor and the infamous Lambda sensor. I checked the 5v first and all was sound with that.

Time for a rethink

The next check was the mapping sensor and this test proved to be the breakthrough that I was looking for. This sensor is a ‘digital type’ and is much faster than the old analogue type. With the engine running I attempted to open the throttle fully. The engine RPM rose and then gradually fell before cutting out as if it had run out of petrol. After conducting the test three times, the output of the mapping sensor frequently rose accordingly with the engine RPM, suggesting that there was no problem in this area.

Now I finally had something concrete to go on: fuel flow and pressure regulation. This was a very strange situation as fuel supply problems normally occur in the power band, which would lead to a severe drivability problem – lack of power. However, I was not entirely happy with the top-end performance so felt it was time to carry out a test on the fuel pump.

Testing the fuel pump

Firstly I went to look around the fuel pod for the pressure regulator, but it was nowhere to be seen!The rail had both supply and return pipes fitted, so the only other place it could have been fitted is in the fuel pump return. These pumps are fitted in the tank underneath the rear seat and I intended to carry out a two-fold test: the first was to connect the fuel pressure gauge to the return flow; and the second was to connect the scope to the 12v supply and also use the ground wire to the pump.

Fuel pump

With the engine running and the fuel pressure reading under 2 bar, the voltage was stable at 12.8 volts, however the fuel pressure started to drop rapidly and the engine started to run lumpy although the voltage still remained stable. Once the car cut out, the voltage went down and shut off the relay (as it should). This test was carried out three times.

I had now reached my decision that the fuel pump was at fault and I would remove the pump for a more thorough investigation. I couldn’t see any damage or blockage – the regulator was fitted to the pump on the return circuit and was of a ‘fired-type’ and the pump speed was varied to generate the pressure. Finally I had something positive to report to the customer!

I replaced the fuel pump with a quality Bosch replacement, the car was then retested and the problem was solved.

Every so often a problem job like this will come knocking where there are no DTC’s logged and the fact that it turned out to be a faulty fuel pump was very strange indeed. In the past I have often come across fuelling issues – which usually result in a lack of power or non-starters – and in some cases a DTC would be logged. In the case of BMW in particular, at least three vehicles were down on power and in all cases the fuel pump proved to be at fault.

Andy’s Final Thoughts 

It was obvious to me that my new customer, like others before her had fallen into the hands of what I describe as ‘Fault Code Jockey’s’. By this I mean that you’ll often read adverts in the local paper saying: “We have the latest in diagnostic equipment that can pin-point any fault”, however If that was the case I would be a millionaire by now!

Every aspect of a fault must be reviewed and tested and such a job can be very challenging. As such, knowledge is not only needed but in a lot of cases it is also gained. Using BMW as an example, a faulty fuel pump can log a DTC of ‘lean fuel mixture’ and ‘Lambda sensor’ but that doesn’t automatically mean you have found the problem and doesn’t even guarantee that there is a base to start with. Therefore it should be remembered that regardless of how committed you may be, there is always room for improvement!

Why does poor turbo boost occur?

Unfortunately, simply installing a direct replacement may not be the end of the story when a workshop is faced with a problematic turbocharger.

If performance problems in a petrol-engine vehicle persist, even after the replacement has been fitted, the issue may well be due to a malfunctioning recirculation air valve (RAV).

If the RAV is damaged or malfunctioning, the inevitable result is poor engine responsiveness and, to make matters worse, the problem could even lead to the turbocharger failing as a result of it being overloaded.

The RAV is installed either directly on the turbocharger itself or in the pressure side area of the charge air line. Poor engine performance can be caused by factors such as a ruptured membrane on the inside, leaking control lines or corroded plug contacts.

With electronic RAVs, an entry is generally created in the ECU, so checking the fault memory will save workshops a lot of time and unnecessary labour.

What does a RAV do?
The task of the RAV is to take a proactive measure against turbo lag by preventing a backlog of charge air, which can accumulate as a result of gearshifts and causes the deceleration of the rotating assembly.

If the driver suddenly eases off the accelerator pedal at high turbocharger speed, it will cause the throttle valve to close and high dynamic pressure to be generated on the compressor side, which cannot escape. This counter pressure drastically slows down the impeller and leads to high mechanical loads on the turbocharger and the closed throttle valve. Once the gear change is completed and the throttle valve reopens, the turbocharger has to be brought up to speed again, which is why there is a delay.

RAVs minimise the delay following these load changes – commonly known as turbo lag – by releasing the accumulated charge air between the compressor side and the closed throttle valve via a bypass. Once it has passed through the compressor, it is guided back into the intake section ahead of the turbocharger.

This loss of pressure on the compressor side prevents a deceleration of the impeller and when the throttle valve reopens, the RAV closes and the boost pressure increases immediately. Therefore a noticeable drop in performance should always lead technicians to check the RAV before replacing the turbocharger.

Turbo range
Through its joint venture with Bosch, MAHLE Aftermarket is now able to supply the UK aftermarket with an extensive range of OE quality turbochargers for petrol engines developing 45-220 kW and diesel engines rated between 35-165kW.

Latest additions to the MAHLE Original range are part numbers 011TC17498000 for four cylinder 92kW engines fitted to Vauxhall Vectra, Saab 9-3 and various Volvo models, 082TC14411000 for four cylinder 135kW engines used in BMW 3 Series and X5 models and 222TC15242000 for three cylinder engines fitted to the Smart range.