CarlK920

I have an 87 951. For 3 of the last 4 winters, when parked, the clutch pedal goes to the floor (or when pushed, goes to the floor without engaging the clutch) and fails to work. Previous years, the local mechanic (not Porsche but pretty good -- I think) has replaced the clutch master cylinder. Last time he said he just cleaned it and put it back in, and it actually made it through the winter (with occassional use) and all of last summer. (He hasn't replaced the slave -- said it worked well; and haven't had any problems with that -- as far as I know anyway.)

This winter parked in my Dad's garage 200 miles away; about 3 weeks later (some VERY cold weather, in an unheated garage) went to move it -- same problem .. clutch to floor and not functioning. I'm assuming its again the master cylinder that isn't functioning, so I've purchased a new master cylinder, and am trying to get a shop manual/info for the local guys who've never worked on a Porsche before! (scary, I know - but its either that or haul it 200 miles to the guy who has been good at fixing it, but not really solving why it keeps doing the same thing over and over again .... that's what I get for owning a Porsche in western ND without a ton of money or the mechanical skills and equipment to do the work myself, right?!)

BUT, before having them tear everything apart ... from what I've read here it sounds like maybe I'm getting air in the system somehow when it is parked.
Does this make sense??

If so, .. is there anyway to solve this without having them tear out and replace the master cylinder??

Anyone have any ideas on why this keeps recurring?? (Clutch seems to work well at other times, with just a bit of "stickiness" at floor in cold weather). This gets a little old, year after year!

Sorry about the length of this .. I'm a newbie .. but wanted to let you know the "history" of this!!

Thanks for any help!!

tod84944

Sounds like the slave cylinder. If you were getting air in the system, it would be doing that while you were using the car. Check the resivor and make sure that it is full. You might have a leak at the bottom of it and all of the fluid leaked out. But, ever time I have had one of mine with the clutch pedal on the floor, it was always the slave cylinder. Which, is a lot easier to change than the master cylinder.

nine-44

Has he changed the fluid? Maybe contamination is killing the new master? The fluid level has to be kinda high in these cars, the clutch feeds high in the reservior.Maybe he has never bled it properly and the air is rising to the master, going dry and sticking to the floor. They are a pain to bleed out all the way. Good luck, you'll find an answer here, let some others post. It sounds goofy to me.

KuHL 951

I have a hunch that really cold weather must cause the seal to retract a bit on the first push of the pedal letting in some air. So many folks have complained of the same thing in real cold temps. Any chance that moisture was never completely flushed from the system?

Tom M'Guinn

Ever had the clutch and throw-out bearing and arm checked? I'm wondering if something is bent and causing the master or slave to extend or compress beyond their intended range? Other than that, I second the suggestion to make sure the fluid is clean, including the reservoir and lines. BTW, don't forget to check the hard/soft line running between the master and slave. When I did mine, I first replaced the slave. Then the master popped and I replaced it. Then the line started leaking and I replaced it. Now it seems to be holding...

CarlK920

Thanks for the ideas .... to answer a question on fluid level: I know the fluid level has stayed high, because I was concerned that this might happen, so I've checked often .. and "topped it off" just before parking and it was still full when I checked now with the pedal on the floor/nonfunctioning
It is possible that their is some contamination going on ... one year anyway there was some dark streaks in the fluid in the reservoir ... don't think that was the case this time though.
As for the possibility that it hasn't been bled properly in the past ... this last time it worked well for 18 months .... then parked in the cold and goes bad by itself ???

CarlK920

The cold weather on the seals is consistent with the history ... at least most of it. Last winter it was in a garage that wasn't heated, but is attached to my house, so it wasn't as cold. This winter it was in an unattached garage with cold (I mean COLD, as in -25!!) weather before I tried it again.
If that may be the case ... and the seals get warmed up again ... is there a way to try "fix" it without pulling the master cylinder apart?
Also, to make sure I'm being clear -- when I say the pedal goes to the floor, I mean it goes to the floor but without doing anything ... I don't know whether you'd say the clutch is "engaged" or not engaged (sorry, about not having the terminology right!) ... but, what happens is the clutch basically stops working ... the pedal doesn nothing ... if I'd start it in gear it would move, but couldn't shift. There was a suggestion that this means the slave is bad -- not the master -- does that makes sense?
Thanks again for the ideas and help!

Luis de Prat

And that sounds exactly like the cause of your problem, due to 1) the symptoms, and 2) the fact you've only replaced the master cylinder.

KuHL 951

I misread the first post. I thought your mechanic replaced both M/C and slave. Replace the slave cylinder for sure. I would buy a bottle of cheap brake fluid and use it to flush the entire system, including brakes. Then start from scratch with a good fluid like ATE. A Motive bleeder will make this task so much easier. My slave failed suddenly on a cold morning after sitting for a week.

hosrom_951

Don't forget the intermediate hose that runs between the clutch master and slave cylinder(s).

Luis de Prat

Huh?

hosrom_951

There is a hose running between the clutch master and slave cylinders, that would need replacement if either the master cylinder or slave cylinder leak.

Luis de Prat

Unless you're referring to the blue brake reservoir hose, which can be replaced if necessary I don't believe the hose between master and slave is a maintenance item.

Master or slave will leak due to failed seals or scoring by the piston within the cylinder, not because of the hose.

Tom M'Guinn

Actually, my hose did leak. There is a junction point where the hard line is connected to the rubber part, and it can leak there. As I mention, my hydraulics failed one part after another, until I had a new slave, master, and hose in between.

hosrom_951

I just ordered all three parts (clutch master cylinder, slave cylinder and hose).

The hose was for ~$20, and doing a search proved that if the master and/or slave cylinders fail (leak), the hose should be replaced since that also fails (highly recommended and as Tom said and experienced).