Clutch master or slave cylinder issue?

*** UPDATE - 4 years and 60 thousand miles later I got the car back to fix the clutch ***

I've been working on a coworkers 98 Beetle TDI - just finished up a ton of work and it's running great but the clutch hasn't been right since he bought it. No slipping - but released pretty much at the floor. I bled out the brakes and the clutch cylinders (super blue racing fluid) and it got a bit better. Didn't have to mash it into the carpet, but was still very low.

As I was driving it back to him, I noticed that if I pumped the clutch about 10 times it released at the normal height. After a while, it would go back to releasing at the floor (pedal movement has always felt normal).

I'm guessing that the clutch master cylinder has a bad seal, but I guess it could be the slave cylinder too. Any way to isolate one from the other, or should I plan on replacing both?

Unless I hear otherwise (or he wants to just go for both), I guess I'll start with the clutch master cylinder since I have heard of one causing a similar problem. The only slave cylinder I've had fail leaked fluid all over the place. I'm assuming that the fluid is bypassing a seal and going back to the brake reservoir since there are no leaks.

I'd like to know if this works.

I will post a follow-up when I have the car back to work on. His previous daily driver (old Saab 900 turbo) is really hurting so it may be a while before he can hand the beetle over again. I did find one similar thread, but the poster never responded with his results.

Hey mate am having a simerlar problem with my brakes on my mk4 TDi, I up rated the calipers and the brakes where really spongey, but now they have gone the oppisite and keep siezeing up on me and a have too keep pulling up on side of the road and lossing the nipples too let the prssure out? :s has any one else had this problem if so can any one help ?

John,

If the slave is being bypassed then you'll have brake fluid present in the boot inside the bellhousing. My money is on the mc.

gotgolf18 said:

Hey mate am having a simerlar problem with my brakes on my mk4 TDi, I up rated the calipers and the brakes where really spongey, but now they have gone the oppisite and keep siezeing up on me and a have too keep pulling up on side of the road and lossing the nipples too let the prssure out? :s has any one else had this problem if so can any one help ?

Click to expand...

The only time I've seen that is with a restriction in the line somewhere - fluid pressure is high enough to push past, but it prevents return flow. Swelling or miss-routing of rubber hoses are the main culprits. It sounds like you have a problem with more than one caliper? If that's correct, I would think the master cylinder would be the problem.

Greengeeker - thanks for confirming my suspicions.

The clutch in 99.5 in my sig is getting REALLY low too(A G60/VR6 clutch is on my to-do list right now). Had an aftermarket carpet and had to cut the front part off due to the clutch not being to disengage all the way.LOL I think that is how the LUK clutches fail when they get worn. Since it is a 98NB, it should have a LUK clutch.

How many miles on the NB?

It only has 93k miles on it. I thought the clutch was the problem until I pumped the pedal and it came up to normal. I won't rule it out though...

What did you find out?

nothing yet.... he loves driving it too much to give it up. Mentioned that the hill he needed to downshift to second to climb before I did the timing belt and intake cleaning he could now climb in 5th with no problem. Here was the thread with some pics of the work I did: http://forums.tdiclub.com/showthread.php?t=285331

Unless the clutch gets worse, it'll probably be a while before I end up with it again.

Hey guys thanks for the help and sorry about the late reply, it was brake switch, a dint put it in right!

Thanks Chris

Can anyone shed some light on Chris's post? I don't see how a brake switch can cause brake lockup. Maybe if it keeps the pedal from coming all the way back up, physically blocking travel? Electrical mis-operation would not cause this, would it?

I have known two people that have had the clutch release lever crack and bend on them. The pedal travel gets longer and longer, the slave cylinder and the master cylinder were fine.
One way to tell is that the bent lever is further from the slave cylinder as it gets worse. I will take some depth readings on a known good clutch and lever today.

I second the clutch release lever .I had one on a 2000 New Beetle with the same problem.
Later

The lever can be pushed in 11/16" when measured from the mounting surface of the slave cylinder. This is with no effort, just pushing the throwout (release) bearing up to where it touched the clutch fingers. The measurement was done with a 1" wide carpenters tape, and so was not to the bottom of the dimple that the slave cylinder pushes on.

When the lever was hooked and pulled towards the opening, it would lay flat up against the inside edge of the mount.

This was with a new throwout bearing, lever and Sachs clutch from IDparts.com.

4 years and 60 thousand miles later I finally got to work on the car DMF was shot. Did a full clutch replacement and it's good to go.

More details here: http://forums.tdiclub.com/showthread.php?t=333365

LOL, bet there lots of members waiting to find out. Nicely wrapped up

muzy said:

LOL, bet there lots of members waiting to find out. Nicely wrapped up

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I was one of them He's been running it hard for the last 4 years. Double clutching / rev matching and occasional slamming into gear. Once shifter parts started to break he decided to have it fixed.
Couple pics:
Rubbing inside transmission:

New vs. old throw out 'arms' - still decent:

Really bad DMF (bad enough to turn by hand):

gotgolf18 said:

Hey mate am having a simerlar problem with my brakes on my mk4 TDi, I up rated the calipers and the brakes where really spongey, but now they have gone the oppisite and keep siezeing up on me and a have too keep pulling up on side of the road and lossing the nipples too let the prssure out? :s has any one else had this problem if so can any one help ?

Click to expand...

Water in your brake fluid can do this.. Just normal braking will heat the water in the fluid and it will expand much more than brake fluid does, putting pressure on the brakes. Also, did you check out, and grease the slides for the caliper when you were in there?