VW Tiguan 2010

Monday we got a VW Tiguan 2010 diesel in because the customer advised his clutch pedal was operating close to the floor. The pedal effort had been at least 75% lost within its working stroke. I was asked to check the clutch master cylinder and told these are somewhat difficult to access and remove!

I saw what I thought looked like dampness of fluid on the clutch master cylinder primary push rod. I suspected the cylinder was faulty. The fluid level however had not reduced and I could not visually see any signs of a leak. Rightly or wrongly I advised the boss I thought the master cylinder appeared to be leaking. He got a master cylinder and told me to fit it. I explained that I'd never fitted one on these models before. I decided to look on AD for a time to remove and fit the master cylinder. 1.70 hours was quoted. I then utubed the car and a guy on there had removed the DPF for some reason and put me off wanting to do the job!

The AC piping and heat shieldings covering the bulkhead wall was also off putting making me think the job was more difficult than expected. 

Anyway for what its worth, this might help others...

1 / Unclip the cloth type head shielding from the brake master cylinder hose and fold it back towards the passenger side bulkhead area just enough to gave clear access to the master cylinder tubes and electrical connector.

2 / Put rags underside the master cylinder area for the clutch.

3 / Pull off the feed pipe from the clutch master cylinder and turn it so that it is facing upwards to stop the brake reservoir fluid emptying.

4 / Unclip the electrical connector from the clutch master cylinder.

5 / Working from the frontal view of the outlet pipe from the clutch master cylinder, and using a small pick, pull the spring clip towards you gently to release the outlet fluid pipe from the clutch master cylinder. When you unclip the steel fluid pipe from the bulkhead wall and then push down on the 90 degree bend of the pipe to release it from the clutch master cylinder, make sure you keep your eye on the "top hat shape seal" that will fall out onto your rags that you safely placed underneath the master cylinder early. (IF you lose it you need to buy a new pipe, which is very expensive)

6 / Working inside the drivers compartment lower pedal box area you can see two 13 mm nuts. Remove them. Looking through the lower dash panel at the lower column area and shining the hand lamp away from you behind the lower dash panel you will see the one remaining upper 13 mm nut. Using a long 3/8 drive extenson and ratchet remove the 13 mm nut.


7 / The master cylinder can now be removed from the underside lower bulkhead dash area.


8 / The master cylinder twists 90 degrees to release it from the pedal box. Secure the pedal box in the vice and using two pairs of hands push together the white plastic clip within the pedal box that secures the master cylinder push rod to the pedal.

Note. the white clip once removed is in two halves. The clip is not broken, it is designed that way.

9 / To refit the clip on the new master cylinder push rod, place both halves of the plastic clip around the ball end of the push rod and then locate and push back into the pedal until you feel and hear the clip click into position. Rotate the master cylinder 90 degrees to lock it back into the pedal box.

The remainder of refitting is the reverse of the above. It took me about 15 minutes to remove the pedal box completely.

Now the problems...


I primed the hydraulics using a pressure bleeder and was more than happy with the quality of operation of the clutch pedal, i.e. no sponginess or sagging pedal. I then road tested the car and all seemed fine. No gear crunching or notchy operation. The following day the customer complained the clutch pedal had dropped!!


So I checked it and found that the quality of feel seemed to suggest either a leak or trapped air. I primed the system again and the pedal felt normal again, so I went to road test it but this time the pedal was failing as I was exiting the garage doors. All this occurred Tuesday evening.


Thursday afternoon...

I primed the system and pressure tested it for leaks, either internal or external. No pressure loss. I tried both static pressure tests and dynamic tests and found no leaks. 

I tried manually bleeding the hydraulic system but learned that the clutch master cylinder when the pedal was depressed would not push the fluid through the system. When I pressure blead the system the fluid would pass through the system only when the clutch pedal was fully released. When I depressed the pedal fluid would stop exiting the clutch slave cylinder bleed valve.

At this point I felt that the master cylinder could be faulty?

The boss contacted someone (I assume LUK) who told me that the brake reservoir fluid cap vent could be blocked and cause this fault! I asked why the braking system was not affected but he said the braking system would not be affected by a blocked vent? He also advised about the pressure regulating valve within the clutch hydraulic line to the clutch slave cylinder. He advised that sediment and contaminated brake fluid builds up in this valve and causes the pedal to dip and sag in operation.

The brake fluid is brand new going in and brand new coming out. Nothing along the lines of contamination can be visually seen. He insisted the pressure valve would be the cause.

I've removed it ready for a clean out with brake fluid and a air line tomorrow. I'll have to see whether he is correct or not?

To be continued...