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.

 

Subscribe!!!I would love to know more about this check valve and his function.....TSB 4897????

 

I have my old power steering pump out of my car and it is sitting full of fluid so it did not dry out. let me know if you cant get parts.

 

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. Sorry Marskii if I'm stepping on your similar post

 

I did exactly what you are going to do! It was an interesting operation to discover a piston with two heads having steering pressure being applied constantly to one of the two head and the other head receive pressure from the clutch pedal actuation.....

 

JPflip, Thank you very much for the pics. It is indeed a complex system. In looking at the pics, is it you estimation the "x" and "y" photo's are the check valve? Based upon the location and where the lines are, that would be my guess. When you took it apart, was there any noticeable damage to any of the parts in the x or y area? I guess I will have to pick up a new slave and see if the old one will offer up any secrets. What was your conclusion as to the failure of your slave?

 

"JPflip, Thank you very much for the pics."

Your welcome!

"It is indeed a complex system. In looking at the pics, is it you estimation the "x" and "y" photo's are the check valve? "

It is in fact a check valve but I wonder also if it is a relief valve also. The difficult part was to follow the oil passage inside the body of the valve....

"Based upon the location and where the lines are, that would be my guess."

Good guess....

"When you took it apart, was there any noticeable damage to any of the parts in the x or y area?"

Nothing at all!!!! I am used to repair aircraft hydraulic systems and Iwhen I started the dismantling of the valve I was sure to found something... Nothing at all, the o-rings were in good shape and there was no erosion or damaged of any kind. The only thing I could not do is a test of spring pressure that can become weak after some times....Of course we don't have any replacement parts and let me tell you some of the o-rings are difficult and may be impossible to found...

"I guess I will have to pick up a new slave and see if the old one will offer up any secrets. What was your conclusion as to the failure of your slave?"

Feel bad to say that after trying to discover the secret of the weakness of those valves I came out without any positive answers....

I got another damaged one and may be one day I will do another attempt to found the reason why we got so many problems with these valves

Remember most of our problems are fluid migration. Fluid migrate from the high pressure, power steering pump, to the low pressure, clutch pedal hydraulic actuating mechanism. I was almost certain to found the o-rings on the double head piston damaged and I was sure the fluid was migrating exactly there. But I was wrong the o-rings at that location were perfect and the cylinder looks good too.....

Keep us inform if you are trying to get into the heart of this valve!