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AudiDoc
AudiDoc, ASE Certified Technician
Category: Audi
Satisfied Customers: 6458
Experience:  Independent European garage owner. Over 20 years experience
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My 2002 audi tt, has a weird problem. the clutch pedal drops

Customer Question

My 2002 audi tt, has a weird problem. the clutch pedal drops to the floor after driving for 10+ miles without a gear change, its fine when cold, its fine when driving around town, it just seems to happen after a reasonable drive, If you then pull the clutch pedal back up & wait about 5 mins its fine, possibly a little spongy at first.
Had the master cylinder changed but dont want to gamble on the slave cylinder due to costs
Submitted: 4 years ago.
Category: Audi
Expert:  AudiDoc replied 4 years ago.
Hello, I'm Jason and will be helping you with your TT problem.

If the master cylinder is new, properly bled out, and there are no obvious fluid leaks externally, then the issue is likely the slave cylinder/release bearing. If the brake fluid level is dropping at all, or you're seeing any fluid build up at the bottom of the transmission bellhousing, this will also confirm my suspicion.
Customer: replied 4 years ago.
There's no leaks, or fluid level dropping, if it was the slave, why is the problem happening once the car is driven, without gear changes, it's not making sence, I'm not a mechanic but I understand hydraulic systems, if it was a blocked return, it would happen on clutch use, as it would if the slave was leaking.
As I said in the question, it only happens when you depress the clutch after a reasonable drive without gear changes
Expert:  AudiDoc replied 4 years ago.
Did this start happening before replacing the master? Also, if you stay stationary, with the car in gear, clutch pedal depressed, does the car ever feel like it wants to "creep" at all?
Customer: replied 4 years ago.
It happened before the master was changed, the car doesn't creep or try, the revs are also stable to prove this as well
Expert:  AudiDoc replied 4 years ago.
Hmmm, this is a curious one for sure, especially with no fluid loss.

However, with that said, externally, there can only be two external variables that will affect your pedal.

1) master cylinder - changed
2) air in the system. I actually recommend a back-bleed on these. I've had to do it on mine, and a few R32's. This will require a special setup to backfill the system through the bleeder fitting on top of the bellhousing.

However, if those two items are in good shape, then the big expense comes next, and these gearboxes are not fun at all to remove. I also recommend staying with a stock LUK clutch kit, rather than going aftermarket, since slave cylinder dimensions are often not perfect on the aftermarket setups.