RangerDick

Trying to diagnose an intermittent stiff clutch pedal. I replaced the accumulator about 2 weeks ago. Since then, the pedal is usually fine in the morning after sitting, but on a few occasions, it has been stiff. Nothing regular and not a pattern I can find.

In reading about the issue and reviewing the factory manual, it appears the diagnosis may be a faulty check valve in the power steering reservoir or the slave cylinder. If that is the case, I know Porsche recommends replacing the whole item, but I was wondering, has anyone actually taken apart the check valve in either system rather then buying the whole new part? It appears you can dis-assemble the reservoir, so the valve must be inside. Knowing Porsche though, it is probably sealed inside and not accessible. But being a curious type of person, I want to see if I can figgure it out.

I am going to do the factory diagnosis tomorrow of the check valves. If it points to one valve or the other, I will probably take apart the bad one, but I wanted to get some opinions from others to see what is in-store for me.

BTW, the accumulator took about 20 minutes. But grinding the wrench and bending it took over an hour. If you are local Bay Area, I have the wrench available to loan out.

jpflip

This is really interesting. Numerous questions came to my mind about this check valve inside the reservoir. Please keep us inform if you go into this depth!

Macster

We probably have the same info... but if there is no hydraulic clutch boost after a hold time of 24 hours at least one of the two valves is bad.

There are two tests to check the functioning of the valves. I won't type the test steps in but if the lower valve which is directly testable is ok the upper valve is bad.

The factory manual states the upper part of the tank can be replaced, this is the part that has the new upper valve.

However, Porsche no longer offers the upper tank part separately, if it ever did.

When one of the valves got noisy (high pitched squeal) the tech replaced the tank with of course new valves. I believe the tech told me the noisy valve was the upper one.

The old tank -- I have it at home -- has a top that looks like it can be removed. I have not done this. The tech told me the valves are not servicable -- they may not be as far as Porsche is concerned -- but I have not removed the tank top and looked for myself.

Sincerely,

Macster.

C5Driver951

Well, take that thing apart and take pics.

I'm sure a lot of us would like to see what you find. I'm certain at least on of my valves is bad as I know it isn't the accumulator.

Kevin

I wouldn't mess with it. It was the check valve that cause a handful of engine car fires. Infact if you search on Rennlist you will find a members car going up in smoke with pictures. This issues has been fixed with the new 997TT unit. Install it and don't look back.

C5Driver951

The voice of reason speaks.

From your experience does changing the reservoir with or without the slave and accumulator get rid of the common failure mode with the clutch system? Of not, I'm just going GT2 style... I'd like the consistent feel in the pedal too.

Kevin

You still retain the power steering pump and check valve regardless of the "CLUTCH" system. It's the back half of the power steering pump that supplies the Pentosin to the assisted slave.

If your desires are to remove the hydraulically assisted clutch>> I prefer to do this when one does a clutch kit. Drill the bell housing and mount the proper GT3/GT2 slave on the drivers side of the tranny. Go one step further and order up the correct GT2/GT3/Tiptronic power steering tank and power steering pump. In the end you will spend $200 more, but you will have a factory system that any dealer of shop can order parts for.

C5Driver951

Thanks, Kevin. What I really desire is a reliable clutch actuation with a consistent feel that I don't have to continually throw parts at.

The clutch was replaced prior to me buying the car, and is fairly new. I don't mind the hydraulic assist, and if the assist, slave, accumulator system were reliable, I would only have one issue with it. I find the random nature of the pickup point to be rather frustrating.

I'm happy to do it right and only do it once. However, it seems the clutch/slave and pump don't seem to make that an option whereas the GT2/GT3 pump, slave with the removal of the hydraulic assist seem much more reliable and consistent.

What I thought you were talking about with the 997TT pump is a separate issue.

RangerDick

Ok, so my results from the diagnosis of the two check valves indicate the slave cylinder check valve is bad. This was done by disconnecting the return line from the reservoir tank and measuring the amount of pentosin which came out of the tube, over an hour period- max 4cc's. When I cracked the tube, way more then that came out initially, so based upon the diagnosis, it points to a bad slave cylinder. So it's either a slave cylinder or GT-2 conversion.

I'm not in the mood right now to drop everything and drill and tap the bell housing, so I will probably take Kevin's advice and wait till I can do "everything" on an engine out occasion. I do not have any fluid migration or other issues related to a bad slave. It was replaced about 11000 miles ago, but it was 3 years time wise. I also don't have any reservoir whine, whirl or whistle, so for now, it looks like my power steering pump check valve is still good. What is kind of amazing is how cheap the retainer ring is which holds in the return lines. I'm surprised there have not been more leaks and fires reported.

Before I proceed, does anyone have an old, or junk slave cylinder they are willing to donate for a tear down? I'd love to pull it apart and have a look at the pistons, check valves and seals? I'll pay postage and a nominal core charge

Kevinmacd

Well I just did the slave and accumulator. I forgot how easy the clutch used to be! No more overflow from the reservoir, even though it was slight, I did notice that at times prior to the repair, the clutch would disengage at different distances. All fixed!

"02996ttx50

i hate the intermittent "notchy" startup feel of the stock clutch setup exhibited when the accumulator is beginning to "go". my last new accumulator lasted a total of 6 weeks before it began to show symptoms of failure. i know it's only a matter of time ( again argh ). i can't believe i'm saying this, but i almost wish i needed a new clutch to install the oem gt2 setup, per kevin's advice, which sounds very solid, compared to the other setup i.e. non oem. i can already envision how much i would enjoy the non assisted feel. it would certainly be better suited to the other rough and tumble aspects of my car's current setup.

rangerdick.. keep an eye on that sucker.. and don't engage/disengage the clutch indiscriminately with engine off, eg the multi "pump" clutch "test" of a failing accumulator. that will NOT help it. this i know.. and good luck with it.

Macster

While I wasn't told this by the techs and it wasn't mentioned in the factory manual I suspect the pump test of the clutch is only intended to be used to confirm a suspected clutch accumulator is not working properly.

It is not intended to be a test used every day to keep tabs on the accumulator's health.

A bad accumulator is pretty obvious in that if one gets in the car after the car has sat say overnight unused and the clutch pedal is hard before the engine is started the accumulator is bad.

With the car at the service department then the tech would walk through the test steps to confirm this diagnosis and test the clutch hydraulic power system to make sure this was not at fault. The accumulator can't accumulate pressure for boost assist if pressure is not being supplied due to a faulty hydraulic system.

Sincerely,

Macster.