Clutch Master Slave Cylinder replace problem

I recently replaced clutch master and slave cylinder. 98 Jetta MK3/AHU. Clutch was working but a bit difficult to get into first. I figured at 430k miles fresh clutch hydraulics couldn't hurt (and might even help).

Wow that master cylinder R&R was a PITA, especially the top bolt on the bracket that covers the cylinder mounting nuts behind the clutch pedal. Ugh.

So, got all installed and thought I did a good bleed job (two person style). But afterwards, clutch pedal didn't come up as high as normal, you could get the last 1/2" or so of upward pedal travel by pulling on the pedal, but at that point the plastic clip on the pushrod would be disconnecting from the pedal. Later I realized my cruise control wasn't working because the clutch pedal switch never made contact (even AFTER pulling pedal up as far as possible, still not enough to close the switch). I verified this with a temporary shim about 1/4" between pedal and switch which cured the cruise.

So, my thought was somehow the master cylinder pushrod was too short. So, I gritted my teeth and took it out, compared compressed and extended position with original VW cylinder and found them to be about the same (WHAT??).

Now I'm puzzled. Maybe something about the new/old slave cylinder are different, maybe I somehow didn't get the system completely bled correctly? There could be something wrong with clutch itself, but why would old cylinders work and not new?

I guess my plan is to remove the slave and compare to old. But if they're the same what's next? Don't want to be swapping master cylinder back and forth with the effort involved.

Any ideas/suggestions would be greatly appreciated!

Reverse bleed the system. Air likes to go up, not down.

-Todd

I recently went through a similar ordeal with my 97 B4. At 270K Clutch started having problems fully disengaging. (trouble with first) Tried bleeding system every which way, things only got worse. Bought a power bleeder, success! (I vaguely recall flushing brake system prior to this - so maybe the clutch ingested air)

About a year later, ran the system dry when a brake line went. Replaced brake line, power bled system, trouble disengaging. Must be air - Bled and reBled. It has to be air, it was working fine before.... Not so much. Installed a new clutch master and slave which made the situation worse. Power bled over and over again, different bad result each time...re-installed old master and slave, got it to the point it would shift again. The next day it wouldn't. Short story long, pulled the transmission, found a piece of broken clutch spring wedged in the pressure plate. BTW, pedal was doing the same thing, about 1/2" travel left. With the new clutch, that's gone. Being that its hydraulic, I'm not sure that was related to the problem, or it being travel related new clutch vs old. Hopefully your problem is solved w/ bleeding - from what I went through, I had better luck with my old OEM master/slave.

Replaced clutch (and a bunch of other stuff) , took it for a drive and quickly forgot the hours spent working on it. Well worth it!

Broken springs usually do exactly what you said, don’t allow disengagement. I don’t think OP is having that issue, just a low pedal.

FWIW, when I mentioned reverse bleed, yes you could use a power bleeder, but you can do it cheaper. The last time I used a spray bottle and I hobbled some fittings and tubing together and pumped the fluid into the bleeder, to the reservoir.

Pics are blurry, but if you squint just right, you can image what you want it to be...
https://forums.vwvortex.com/showthread.php?6860016-Reverse-bleed-clutch-master

-Todd

Had this issue before. I was bleeding this thing over and over - was on a deadline, had to be at a job out of town so I took off. After several shifts and 300 miles all was well - it bled itself lol.

Following up my original post. In my case the problem turned out to be a defective new master cylinder (Centric 13833008 from RockAuto). I re-installed my original VW cylinder with 430k miles on it and clutch is working well now. So it wasn't a bleeding problem after all.

Comparing old to new master cylinder it was difficult to spot any problem, both same dimensions and new shaft seemed to go all the way in/out OK. But there must have been some travel resistance in actual use which caused the issues I described. RockAuto was kind enough to give me store credit for the return even though I had installed the part and had tossed my original packaging.

98JettaBioDiesel said:

RockAuto was kind enough to give me store credit for the return even though I had installed the part and had tossed my original packaging.

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Sounds like a bit of a screwjob to me. Should be a refund situation, not store credit for your next future defective brand-new part.

turbodieseldyke said:

Sounds like a bit of a screwjob to me. Should be a refund situation, not store credit for your next future defective brand-new part.

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I've purchased a lot over the years, not very happy with RA myself right now, the shipped part was not the one pictured, they refused to take it back on their own dime, I wasn't about to pay to return it when what was shown was what was supposed to be delivered. Haven't purched from them since then.

Steve

Steve Addy said:

I've purchased a lot over the years, not very happy with RA myself right now, the shipped part was not the one pictured, they refused to take it back on their own dime, I wasn't about to pay to return it when what was shown was what was supposed to be delivered. Haven't purched from them since then.
Steve

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Same here. I have a small box going of parts that they say fit my car, with the correct part number, but in no way fit my model. The cost to return them is too great so there they sit until someone needs them or I use them in another manner, which I have done before.