Bizarre G50 Clutch Bleeding Problem

[Wavey]

I am finally wrapping up my months-long suspension and brake rebuild (new everything). Last night I decided to bleed the clutch system before going to the brakes. The clutch components were not touched during this recent round of work. The G50 clutch fork update had been done by the PO and the clutch has worked flawlessly during the time I've owned the car, but the master and slave cylinders appear to be original.

The brake master cylinder was replaced earlier in the project and the brake lines have been sitting for several months with no fluid in them, although the clutch system was never opened and had the original fluid in it while everything else was getting done.

I filled the MC with fresh Super Blue, hooked up the Motive pressure bleeder and pumped to about 15 psi (1 bar, per the Bentley manual). Bled the system at the slave cylinder and everything is going normally - dirty old fluid for a while, then nice clean Super Blue. Had a few bubbles left so I refilled and did it again. A quick bleed and it appears to be perfect.

Then I go to check the clutch pedal and it drops straight top the floor! I mean ZERO resistance, like it's not even connected to anything. The slightest tap and it falls completely to the floorboard. Pulled it up and tried a few more times - nothing. Also checked for leaks (nothing) and unclamped the vent from the reservoir.

Anyone else encounter this? The only thing I can think of is that somehow the pressure bleeding blew the clutch MC and/or slave seals?

I went ahead and bled the brake system and that went perfectly, but this has me stumped. And I was so close...

[Ned nyna 11]

Wavey,
Look in the inspection port to see if the push rod is against the clutch lever.

[MotoSook]

Never experiences this Dave. I would check the lever to rod action as Ned mentioned. If it's OK, you might manual excercise the MC if it truely is free moving to see if you can't start to build up pressure...just a shot in the dark. Good luck.

[Wavey]

Thanks for the suggestion, but what is that going to tell me? That's a serious question, not a smartass comment. The clutch worked perfectly when the car went up on stands, and nothing in the clutch system, mechanical or hydraulic, was touched during the other repairs. The only thing even remotely associated with this is that the hose from the reservoir was removed when the brake MC was replaced and the reservoir was cleaned out. The hose down to the clutch MC was plugged during that time.

I just pulled the floorboard out to see if I had somehow knocked off the link from the pedal to the clutch master, and everything is fine. I can see the new Super Blue in the tube going into the cylinder. And last night the slave bled perfectly - solid blue fluid, no bubbles - and the bleed screw is tight. I don't see any leaks anywhere in the system.

I just filled the reservoir and hooked up the Motive tank again, pumped it up to 10 psi, and worked the pedal through it's travel a few times. No change. I'm leaving it under pressure for the day in the off-chance that it might make a difference. I'm dressed for work right now, but tonight I will bleed the slave again just in case somehow last night I let the reservoir fluid get below the hose to the clutch MC.

[KTL]

Sounds like you got some air in the system when you did the refill of the pressure bleeder after the first bleeding?

Try again and see what happens.

[Wavey]

It sure does sound like that Kevin. But I'm almost positive the level never got below the hose to the clutch MC. BTW, I'm just using the Motive as a pressure source, and only putting fluid in the car reservoir. I refilled after the first bleed and then bled off maybe 4-5 oz? But if there's air in the line, it must be one Hell of a bubble because there is ZIP at the pedal. I'll try bleeding it again tonight.

[Quicksilver]

Seeing that the clutch system shares the same reservoir it is possible that the pressure bleeder could effect it. The question doesn't make much difference because the only thing that really makes a difference is getting it working.

I have found that bleeding the clutch in these things is a pain even with a pressure bleeder. I have pushed more then a pint of fresh fluid through the clutch and still had air!

The only sure fire way to bleed this that I have found is to unbolt the slave cylinder from the trans and bleed the system with the slave cylinder held vertically with the bleeder at the top.

It is a pain to remount the slave cylinder (I have big mitts) but it has been a sure fired way to get the job done.

[Wavey]

Thanks Wayne. I probably pushed a total of 1/2 quart through last night. Know what you mean about the working space too - I could harldy get the hose on the bleeder.

I guess I'll give that a try as a last resort. What keeps the slave cylinder from popping apart when it's off the car - is there a snap ring holding the piston in? Also seems if I'm going to do that I may as well replace it, and maybe the hose at the back too.

[jm529]

try manual bleeding with the slave in the car. crack the bleeder and have a helper push the pedal down, shut the bleeder and lift the pedal up. repeat until you see fluid without air and getting good pressure.

pressure bleeders are designed to work with larger volumes of fluid like in the brake system. the clutch system doesn't hold enough fluid to need a pressure bleeder.

[Wavey]

I'll try that too if pressure bleeding it again doesn't do it. The problem is there is NOTHING at the pedal - it feels like it's not even connected to anything. I mean not even a bit of sponginess or anything. You would swear there is NO fluid in the lines, but it was bleeding solid fluid last time I bled it. I don't think there would be enough pressure to manually bleed it.

[jm529]

manual bleeding will verify if you pedal is hooked up with you hydraulics.

[Wavey]

Right. Except I'm looking right at it and it's is all there mechanically - push down on the pedal, the pushrod pushes into the master cylinder.

I'm starting to wonder if the piston in the M/C is stuck at the bottom of the bore for some reason. Wouldn't the pressure bleeder push it back out?

[KTL]

After re-reading the original post, it does sound like a failure of the master cylinder. If there is no feeling of pressure resistance, the master is kaput (or the slave) or there is a monster air void in the system somewhere.

Do a test at the slave and see if any fluid can be pushed thru the slave bleeder screw by pushing the pedal. Without the assistance of the power bleeder of course!

Taking out the master cylinder is a PITA. You have to remove the belly pan and unbolt the pedal cluster. Then remove any connections to the cluster in order to get it out of the car, and finally remove the master from the pedal cluster on your bench. I think I recall John Walker saying he finds the master cylinder removal easier than the slave. I think the slave is easier?

I've tried manual bleeding the Porsche clutch and it just doesn't go well. For some reason the master doesn't push enough fluid (or has to push it too far) and the results are marginal at best. I've done a few other clutch bleeds on my Laser and a '96 Pontiac Sunfire. The manual bleed results were much better on those cars. Dunno why the Porsche doesn't fair well with manual bleeding.

[MotoSook]

Originally posted by Wavey
Right. Except I'm looking right at it and it's is all there mechanically - push down on the pedal, the pushrod pushes into the master cylinder.

I'm starting to wonder if the piston in the M/C is stuck at the bottom of the bore for some reason. Wouldn't the pressure bleeder push it back out?

I also thought the MC piston may be bottomed out...hence if you pull up on the rod, then bleed...what happens? If it's not bottomed out...then you might have a bummed MC. You might have a bummed MC if it is all the way down too....isn't their a spring in the MC that returns the piston? I never took apart a clutch MC, but the hydraulic MC is a hydraulic MC......

[axl911]

In my C2 G50, the clutch shares the same fluid resevoir as the brake. However, the pickup point is much higher than the brakes'.

Many times, I bled the brakes using the pressure bleeder, I put air into the clutch and it dropped to the floor.

If you put the SuperBlue into the Motive bleeder itself, then you won't have this problem. Otherwise, always keep your fluid level above half full in the brake resevoir.

---
anthony

[jm529]

there should be a return spring in the master. if its stuck, i'm guessing theres corrosion in the bore and its time for another master.

[Wavey]

Thanks for the responses guys!

Kevin - "...or there is a monster air void in the system somewhere.Do a test at the slave and see if any fluid can be pushed thru the slave bleeder screw by pushing the pedal. " There is absolutely no resistance at the pedal, so I'm thinking that's not going to work. I am thinking monster air bubble though.

Souk - "Hence if you pull up on the rod, then bleed...what happens?" That's the last thing I did, no change. "Isn't their a spring in the MC that returns the piston?" I would think there would have to be, which makes this whole eposide even more strange!

Anthony - I was thinking the same thing earlier today, that I may have forced a huge amount of air into the clutch system when I was bleeding the brakes. I *could* have let the fluid level drop below the clutch hose, really don't think so but it's worth considering. But I did the clutch system first and just concentrated on that before going to the brakes. I would swear that the level never got that low. And the pedal was totally ineffective after the clutch bleeding, before the brake bleeding.

SO - tonight I will put the fluid in the pressure bleeder and give it another try. I keep thinking this has to be something very simple because the clutch system always worked perfectly before, and the only change is the new fluid.

[buttjoint]

I had the same problem. I followed the bentley manual instructions and pumped the pedal slowly while the bleed screw was open, Then with pedal fully depressed close the bleed screw.

[Dixie]

It's something simple. After all, the clutch worked before you worked on the car, didn't it? Did you forgot to bleed the clutch at the slave?

[Wavey]

Uhhh.... yes I bled it at the slave. ???