Need advice from the clutch gurus

Slam · 10-21-2010, 12:10 PM

My 84 944 has developed a clutch issue that's got me thinking it may be time for surgery.

I replaced the slave and master about 4 weeks ago and have had no troubles. Yesterday night it seemed my friction point moved closer to the floor. The clutch engages smoothly, it doesn't slip, and yet the friction point seems to have a mind of its own. This morning it was back where it should be. By the time I got to work, it was near the floor again. The fluid is new, the fluid level is fine, the slave doesn't appear to be leaking. The clutch pedal returns fine and isn't hanging up at all. I'm thinking maybe the TO bearing is hanging or the disc has had it. Is my clutch going out with a whimper instead of a bang? I've had the car for about 7 weeks and was hoping to avoid this kind of thing until next summer.

Am I about to join the ranks of the 944 clutch surgeons? I've done a couple of 924s, so know basically what to expect.

flash968 · 10-21-2010, 12:32 PM

sounds like an air problem to me - use a motive power bleeder

Slam · 10-21-2010, 12:47 PM

Thanks, flash968.

I'm innocent! I DID use a Motive bleeder! Maybe I'll re-bleed tonight. But why would the system bleed down fine and have air show up a month later? Maybe the line is bad.

John_AZ · 10-21-2010, 01:10 PM

Before you bleed again, go under the dash and make sure there is no pressure on the clutch MC caused by the clutch pedal. Loosen the connecting rod between the clutch MC and clutch pedal enough so it is real sloppy.

When you have finished bleeding, adjust the connecting rod so the clutch pedal only has 2-3mm of play at the pedal.

I would also have the rear of the car raised higher than the front. I use a jackstand at max and add a 4x4. Make sure you block the front wheels. The slave could have a pocket of air.

If this does not help, you may have a spongy rubber slave hose that needs to be replaced. The rubber hose only goes about half way up from slave cyl to a connection joint. Common.
Be careful when ordering---many variations and bends in hose. One size does not fit all.

GL
John

Slam · 10-21-2010, 01:18 PM

Righto. Thing is, I went through the procedure as you're describing it when I did the cylinders, and I set the MC up for about 2mm play. I'll have a tinker with the car and get back to you. It seems the issue is pneumatic, not frictional... (said with tongue in cheek).

flash968 · 10-21-2010, 04:15 PM

you might have a leak in the blue line - i had this happen on one car - we would bleed it - everything was great - then we would drive it and there as air in there again - a real pain in the butt - changed out that $3 hose and it was all good

Slam · 10-25-2010, 08:55 AM

^ That occurred to me too, so I checked it when I tore into the car over the weekend. It's not seeping but it's old.

Here's what I found - the slave had failed! I did bleed again and got air so I thought I was ahead of the game. When I cleaned up I noticed a drip from the bellhousing so I pulled the inspection plug and took a bath in brake fluid. Pulled the slave and took it apart to find out what happened. I had rebuilt it only 4 weeks ago and the seals and piston showed no signs of having failed. What was curious was what I can only describe as a wear ridge in the slave's bore. Right the way around inside was a very subtle indent, presumably where the seal rests. I can only surmise that at rest the piston allowed fluid past it due to this. Or perhaps I'd rebuilt a cylinder that had been rebored in the past and was already close to being out of tolerance. I ended up ordering another slave and then using the good piston and seals from the one I'd just rebuilt and putting them in another cylinder I had. We'll see how long this one lasts, but in the event it fails I've got a good one coming, so I'm covered.

Then I bled about a liter of fluid through the system to get the air out. Time-consuming... And compared to my 83, this clutch still doesn't have the take-up I like, even though the clutch wear measurement is 22mm, which is within spec.