Don Carter

I’m new to 5 speeds, and this 87 is really kicking my butt! It’s the car in the “Barn Find” thread but I’m starting a new thread for this clutch problem since I’m having so much trouble figuring it out. Here’s the history….

- Bought car in Feb with clutch not working
- Found a really cheap master cylinder on closeout and rebuilt the MC from inside the car. (the internals were not identical but pretty close, so I went for it) Bought a slave from Roger, bled the system and the clutch worked normally. Drove for a week or so, then the TB light came on momentarily so…
- Took the car down for 6-8 weeks to do a TB/WP job and had to removed the slave to get the flywheel lock in place. When I re-installed the slave, I could never get the clutch to work right and eventually the piston got stuck in the slave. Later inspection of the MC showed chunks of both seals missing.
- I decided to start over and replace everything, so replaced full MC, slave and blue line, all from Roger. Bled system very easily and clutch worked perfectly. Drove a day or two, then decided to install a Lizard shifter. Installed shifter, found rear bushings were completely gone, broke coupler trying to replace bushings, 3 couplers later, got the right one and got it all back together… BUT, the clutch went to the floor after sitting for the 2 weeks or so it took to get all this done.
- After many attempts to bleed and get the clutch working I noticed fluid bulging in the slave dust cover.
- Drained and inspected the slave, could see or feel nothing wrong with the seals, piston or bore.
- Reassembled, bled and clutch worked again. Went for a drive (today) and clutch eventually went to the floor after a couple of miles. (Enjoyed the Lizard until the clutch went out)
- So now MC piston and slave piston seem to be not fully retracted, and sortof stuck half way in their bores. No visible bulge of fluid in the dust cover.

Thanks for reading this far, long I know, but didn't want to leave out anything important.

Any ideas?

Bilal928S4

Where you able to find the missing chunks of the seals? Could they have migrated to a location in the system and giving you these problems?

gruffalo

Clutch bleeding after my tb/wp job almost drove me crazy....

I had to pop the mc piston to let excess air out, before I got it to work.

Others have been successful with other methods, I tried them all with no luck.

Hai gebissen

What fluid are you using?

Herman K

My experience of getting air into the system

The brake/clutch fluid reservoir "clutch section" down pipe/outlet has a build in screen I found that my screen had brake fluid varnish build up restriction 100% flow of the fluid to the MC ones I cleaned out the screen (or replace the reservoir) I never had the problem again.

If the car has had long periods of sitting the brake fluid varnish may have build-up on this screen and causing blockage.

Don Carter

Bilal, never found the chunks, and yes, I think they could have caused the first slave to lock up.

Hai, using Valvoline synthetic.

Herman, I think the flow is good since it will drip steady if I open the bleeder, and when I remove the slave the flow is very strong.

Kevin in Atlanta

Random thoughts...

If you are not losing fluid it is either getting past the seals in the master or slave. Recently my rubber line from the slave to the body developed a pin hole leak. Fluid filled the outer rubber hose before spilling to the ground.

I have always bled my clutches by pushing fluid up through the slave bleeder valve. The whole pump and hold thing has never yielded good results.

Don Carter

No sign of leaks, looked under the dust cover in the MC, no bulging dust cover on the slave. The rubber hose looks like it might have been replaced in recent years, it has that "newer than everything else around it" look.

I did bleed by pumping up from below a couple of times and it seemed to work, but most recently I used the gravity bleed followed by manual pumping of the slave to push air bubbles out and it also seemed to work, at least for a while. I've never used the pump and hold method like with brakes.

jcorenman

What brand? If it was FTE or *** then it was probably OK. But especially on a car that has been sitting, it is important to check the internal bore of the original slave-- any corrosion would tear up the new seals, which may have been what happened.

As Hilton noted in your other thread, I think this has to be a defective slave cylinder. The slave is a dead-end, fluid gets pushed in there from the master and pushes on the slave piston-- there is nowhere else for it to go.

The only way to get fluid into the boot is for it to leak past the slave piston seal, which should never happen.

Interesting. I've also seen a couple of MC's where the piston didn't move far enough back to open the port to the reservoir, post here.

But if fluid flows freely out the slave bleeder with the pedal all the way up, then you are good in that respect. Dripping sounds right, but should flow freely with a few psi from a pressure-bleeder.

Is it a DOT-4 fluid? If so, it should be OK-- although most folks use ATE blue I think. But seal problems (decomposing, leaking, sticking) are usually age or fluid-related... So I would be highly suspicious of the fluid.

Don Carter

Jim,

Thanks for the feedback. After sleeping on it, I'm thinking that when I remove the slave, I will find some fluid under the dust cover which would explain the pedal going to the floor. I'm guessing that there's just not enough to make it bulge yet. If so, at least that will point again to the slave.

Hai gebissen

Is this compatible with DOT-3/DOT-4 conventional brake fluid?

On my Saabs, which are all DOT-3/4 cars, I use ATE Super Blue as a safe upgrade in my brake and clutch systems. I will use it in my 5-speed S4 as well.

Don Carter

According to Valvoline it's compatible
http://www.valvoline.com/products/co...brake-fluid/28

SeanR

I've seen similar when someone inadvertently pressed the clutch pedal down after the slave had been removed. Any chance of this happening when you had it apart?

Don Carter

I've also been reading about the differences in MC's, old vs new. I didn't modify my new one, but it seems the symptoms of this problem is different, grinding gears, clutch not completely disengaging, etc. I can easily pull the piston and cut it down later if needed.

Don Carter

Sean,

I think that may have happened during the early stages with the first MC and slave, but not recently. Not sure why that would cause a problem though. Are you thinking the spring slams the pedal down hard, damaging something internal in the MC?