Brentflyfish

Okay experts – clutch issue on 1994 964
I don’t think it is the clutch itself – am guessing it is the slave cylinder. But here is my attempt to explain the symptoms and you guys please help me out.

I have had the car for about three weeks now driving it daily. On a normal day the pedal would have about half an inch or so of travel with little resistance before I could feel the positive pressure/spring on my foot. I have notices two or three times that when I come out in the morning the clutch pedal is halfway down. One pump and it would spring right back into position. The shifting is smooth and usually engages about half way through the pedal stroke.

Today, I got the car and the pedal was down. This time it did not spring up. I had to push it all the way to the floor to shift and had a little trouble getting it to shift into gear. After driving for about 10 minutes the pedal returned and the car shifted just fine again. It acted just like every other day.

My thought is that there could be a problem with the slave. I have not seen any fluids under the car though which is a little concerning – just a small drop of oil about the size of a quarter near the right rear wheel that is usually only there if parked when hot. It is not a continuous drip, just one or two and then done. I was told during the PPI that the only identified leaks were rocker arms.

The local repair shop quoted me a total of around $500 to replace the slave (assuming that was the problem).

Thoughts? I have a 1994 964

Rocket Rob

$500 to replace the slave? Wow, the shop labor rate must be really high. Its not that hard to replace, if you have the time and inclination.

I would first start with the basics. Moving up in progressive cost and effort.

1) Bleed the clutch.
2) Check the clutch pedal roll pin
3) Replace the slave and slave hose
4) Replace the master

If you have done all 4 steps, then the problem is inside the bell housing.

5) You need to drop the engine and/or tranny to inspect.

My advice is to start with the steps above and hopefully, you don't get to #5.

Brentflyfish

Do my symptoms sound out of line with a problem in the slave? I am inclined to try myself, but have very limited space in which to work.

Rocket Rob

It may be the slave. They have a finite lifespan. But you may be lucky, and just need a bleed.

elbeee964

Sure, the 2nd part is a no-brainer, but Vegas would lay 3:1 odds it's the rubber in the slave gone kablooey (from 15 years hot, remote service.)
All of them go ****-up, given time...

Actually, I think your car likes you -- it's giving lots of heads-up signs -- and not just leaving you suddenly stranded somewhere.

Brentflyfish

She is fun to drive that is for sure - any how toos on bleeding the lines?

Indycam

Is the brake fluid level in the reservoir going down ?

How does a bad slave cylinder cause the pedal to go down overnight ?
If the piston is at the top of its stroke because no one is stepping on the pedal
and the pedal is up , how does the pedal go down ?

If the seal on the master cylinder was leaking when not under pressure ,
the fluid might leak from one side of the piston to the back side of the piston ,
that would let the pedal drop .

Brentflyfish

was wondering the same thing myself. What do others think the issue could be?

Rocket Rob

To bleed the clutch, you need a power bleeder. I use the Motiv Black Label (no affliations). The process is pretty simple.

You will need a jack stands, a 7mm closed end wrench, a power bleeder, a catch bottle, and a clamp for the brake fluid reservior.

Start by jacking up the left rear and remove the tire/wheel. Ensure that you have jack stands under the car.
1) Fill your power bleeder with fluid
2) Attach the power bleeder to the reservior
3) Clamp off the reservior vent
4) Pressurize the power bleeder. I use 20 psi
5) Slip a 7mm closed end wrench onto the slave cylinder's bleed nipple
6) Attach a hose to capture the "old" brake fluid
7) Open the bleed and watch the dirty fluid come out. Keep bleeding until you see no bubbles and clean fluid.
8) close the bleed
9) Hop in car and check clutch feel (note: Only do this with the bleed closed!)
10) Disconnect catch hose
11) De-pressurize the power bleeder
12) Remove power bleeder
13) Reinstall tire, lower down
14) Take for test drive

https://rennlist.com/forums/964-foru...-question.html

To replace the slave and slave hose, see this DIY. https://rennlist.com/forums/964-1989...-save-you.html

Brentflyfish

wow - great info.

So is the group consensus that I either have a need to bleed or replace the slave cylinder? Any reason to look at something else?

John D.

I agree with Rob - it certainly sounds like the slave.. As well, if you have small hands - I can tell you it is *possible* to replace the slave without tearing the engine out. And $500 for installing a replacement slave is a ridiculous number...

I had a 964 C4 engine out recently - and it will be coming back out next week as the disc pressure is too much for Jen. As well - on my 993 C4 - I pulled that engine today. In BOTH cases - I removed the slave while the engine was fully installed (not dropped a few inches, which does make it easier...)

A clutch slave is about $85 (it's an FTE part, BTW) and a clutch master about $125... If you really need more working space up there - you CAN drop the engine about 2" at the rear without much of a problem - but, like I said - it's not required - if you have a good light, smaller hands - and a bit of patience...

As for the rubber hose - if you are doing the slave - you might as well replace that - which is about $30. I've never had the hose go on any of mine - but....

As well - Rob is right on target with bleeding the slave..

Hope this helps!

John

Indycam

How does the slave fail in such a way that the clutch pedal drops over night ?

John D.

When air has been induced into the system it will "collect" as the system rests (typically at the high side of the hose - which rides higher than the slave itself as installed) - the air bubbles will collect into a single larger bubble (apex of the hose connection) - which will drop the pedal. When he pumps the pedal the next morning - the air bubble(s) are dispersed and tries to fill from the reservoir - which is temporary, as there is still air in here.

My question - which leads me to the slave - is somewhere - air was induced into a closed system...

John

Rocket Rob

Indy - While I stand on my recommended troubleshooting procedure, my suspicion is that either the roll pin or clutch master has failed. If the roll pin is partially collapsed, then the spring may not be returning the pedal to the top as it should. If the clutch master has a leak in it, then the pressure plate pressure is causing the pedal not to return to the top.

But you should go through the procedure above before jumping to that. I hope the problem turns out to be something simple and inexpensive to fix.

Indycam

The symptom reported is that on first pump in the morning the pedal was going from down to up .
He parks it with the pedal in the up position and then in the morning it is down .
That would be a funny set of symptoms for a roll pin .

"clutch master has failed."
I got 25 cents on the clutch master .

"then the pressure plate pressure is causing the pedal not to return to the top."
Eh ?