Why is it impossible to bleed a 948 clutch?

Driving home from work last week I lost the clutch pedal, so figured I'd replace the master and slave cylinders. I've done this to probably 10 different cars over the years, including stock 944s and 951s. No big deal.

I'm ready to burn this POS to the ground!

I've spend days and days and quarts of brake fluid presure bleeding from the top down, from the bottom up, and just pumping the pedal with a helper. Nothing but a crap pedal feel with tons of free play in the pedal and the car is undriveable.

What the hell am I suppossed to do?

This is an old LT1 conversion using a '84-'88 C4 Corvette slave cylinder mounted to the bottom of a Renegade Hybrids bellhousing.

Do I rip the damn thing apart and convert to the C5 Corvette internal slave? Would that be any better?

Try un-bolting the slave and then bleed it with the pushrod all the way out. Once bled, re-attach and see if that helped. Face the bleeder valve up higher than the hose. Do not push the pedal down with the slave off though. It would blow the slave apart.

As far as using an internal slave on that setup, I've never done an LT conversion, so I don't know if it'll work or not. That might be a better question for Kent at TPC.

Thank you for the suggestion, but that was a disaster. I pulled the slave, angled the bleeder upward, pressure bled it from above, but then couldn't reinstall the slave. I tried with everything I had, but couldn't force the slave and pushrod assembly back into place without opening the bleeder again.

So I just got soaked with brake fluid and the pedal is worse then when I started.

Went through another bottle of Dot3 pressure bleeding from above and below with the car in various positions. Nothing.

There has to be a way to do this. How are people bleeding these systems?

Sorry to hear about all the troubles but I definitely think Kent is gonna have the secret for ya on lt1 clutch and what not.

Worth the call to Texas, he's got me off the wrong path several times. And when Kent isn't bring me back from the depths of uh-oh's it's usually Bob or rays posts on what I didn't do yet that I should have. Lol

Rob44 wrote:Thank you for the suggestion, but that was a disaster. I pulled the slave, angled the bleeder upward, pressure bled it from above, but then couldn't reinstall the slave. I tried with everything I had, but couldn't force the slave and pushrod assembly back into place without opening the bleeder again.

So I just got soaked with brake fluid and the pedal is worse then when I started.

Went through another bottle of Dot3 pressure bleeding from above and below with the car in various positions. Nothing.

There has to be a way to do this. How are people bleeding these systems?

With that being the case, I believe your clutch master pushrod is adjusted wrong. I bet it has the master cylinder pushed in and is blocking the return port. This would keep you from bleeding it properly, and would prevent you from being able to push the slave cylinder back in by hand. Disconnect the master cylinder pushrod, and see if you can push the slave in. If it works, adjust the pushrod so that there is a small amount of free play in the clutch pedal.

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With that being the case, I believe your clutch master pushrod is adjusted wrong. I bet it has the master cylinder pushed in and is blocking the return port. This would keep you from bleeding it properly, and would prevent you from being able to push the slave cylinder back in by hand. Disconnect the master cylinder pushrod, and see if you can push the slave in. If it works, adjust the pushrod so that there is a small amount of free play in the clutch pedal.[/quote]


You were right about the master cylinder ports blocking the fluid. I finally got back to the car and disconnecting the clutch pedal from the master cylinder allowed me to easily compress the slave cylinder and it's rod to push up air into the fluid reservoir and reinstall the slave without opening the bleeder again.

I had the clutch pedal adjusted so there was just a hair of free play in the pedal before hand, so I don't really understand how it was blocking off the fluid ports in the master cylinder at that setting?

Awesome. Glad you figured it out.

Well, still no clutch. I don't get it. There can't be any air left in this system. Could something have broken in the bellhousing that mimics air in the hydraulics? The clutch works and car can sort of be driven, but barely disengages right on the floor, so I know it's not good for the synchros.

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