Accumulator, Slave, or BOTH?

[D_Nyholm]

I am having trouble determining if I need a Clutch Slave, Accumulator, or both. When I shut the car down, the pedal goes immediately stiff. I also noticed that I have some fluid coming from the front reservoir and the pedal feels notchy and does not have as much assist if you go quickly. I purchased a new accumulator and it looks relatively easy to change, but the slave looks like a PITA. I was thinking of just changing the accumulator to see if that helps, but I am thinking that it is both and I might as well just do them both at the same time. Can anyone give me a definitive answer on what I need?

Thanks in advance,

Dennis

[Loren]

Checking accumulator

1. Cold start engine (accumulator temperature approx. 20°C) and let run for approx. 20 seconds (accumulator is full).

2. With the engine switched off, depress the clutch pedal repeatedly until an abrupt rise in pedal resistance against your foot can be felt (accumulator is empty). While doing this, count the number of depressions

carried out up to the point of the rise in pedal pressure.

3. If the number of times the pedal was depressed is over 35, the accumulator is faulty and must be replaced.

[D_Nyholm]

Checking accumulator

1. Cold start engine (accumulator temperature approx. 20°C) and let run for approx. 20 seconds (accumulator is full).

2. With the engine switched off, depress the clutch pedal repeatedly until an abrupt rise in pedal resistance against your foot can be felt (accumulator is empty). While doing this, count the number of depressions

carried out up to the point of the rise in pedal pressure.

3. If the number of times the pedal was depressed is over 35, the accumulator is faulty and must be replaced.

I guess that is where i am confused. The number of depressions until I get a rise in pedal resistance is 0. It immediately gets tough. According to that then the accumulator is NOT faulty? Why does it instantly get tought to press?

[Loren]

I would get some Pentosin and bleed the clutch circuit to make sure you don't have trapped air somewhere.

At this point it would appear that the problem is air and/or a bad slave cylinder.

[D_Nyholm]

Cool, thanks, that is what I needed. I guess since i have the accumulator, I might as well change it when I pull out the slave. Can't wait to be doing this project on jackstands in my garage... ;)

[Loren]

It will be a tough reach - both are on the top of the transmission (more or less).

[D_Nyholm]

Ya, looks like it'll be a tough one, but with the DIY on here, i think it'll be possible. Since it is the winter, i can't drive the car anyway!! :(

[Chuck Jones]

Most of the time it ends up being the accumulator...but it can end up being both. Remember...that Pentosin is HIGHLY flammable and under pressure. Do yourself a favor and do a search for a DIY on changing it out before you start...there are a number of articles written on the subject in the various Porsche forums.

[D_Nyholm]

Yeah, i already read jpflip's and mikelly's reports and DIY's. It looks like i'll have to pump the pedal more than 25 times and then bleed out most of the excess fluid before i even start to unscrew anything. Along with having a few rags stuffed up around the accumulator to catch any spraying fluid.

Though I am still thinking that the 3-4 hours shop time might be worthwhile since that will only equate to $500+parts. Thought the satisfaction of doing it yourself may outweigh that. I am still trying to figure that one since it sounds like it might be more of a headache than satisfying.

[Chuck Jones]

I bought my accumulator from Sunset Porsche for about....IIRC....$95 or so, and the install was less than an hour's work....once they have it up on a lift you can access it from underneath....given the fact its flammable and hard to get to....I'd just pay to have it done....then you have no worries about it being installed right....unless you're proficient with this sort of thing.

Edited January 1, 2009 by Chuck Jones

[Iceyankee-Tsi]

Greetings everyone:

Please correct me if I am wrong but this particular case seems to be a bad accumulator only. To my knowledge this applies unless you have any type of Pentosin leak in the slave cylinder area. I mean, if it was a damaged slave cylinder you would surely see some sort of leak coming from the push-rod area of the cylinder. Taking as the most probable cause of the leak that the hydraulic seal of the inner piston/cylinder assembly has given up. A lack of Pentosin may also be seen in the reservoir if a defective slave cylinder is suspected. In the other hand, since the accumulator is an enclosed container with an inner bladder(as observed in another post from a member) it makes sense for it to damage under constant use. Providing a harsh clutch engagement.

Andres

[D_Nyholm]

Greetings everyone:

Please correct me if I am wrong but this particular case seems to be a bad accumulator only. To my knowledge this applies unless you have any type of Pentosin leak in the slave cylinder area. I mean, if it was a damaged slave cylinder you would surely see some sort of leak coming from the push-rod area of the cylinder. Taking as the most probable cause of the leak that the hydraulic seal of the inner piston/cylinder assembly has given up. A lack of Pentosin may also be seen in the reservoir if a defective slave cylinder is suspected. In the other hand, since the accumulator is an enclosed container with an inner bladder(as observed in another post from a member) it makes sense for it to damage under constant use. Providing a harsh clutch engagement.

Andres

Any truth in this? From reading i am thinking that since the front reservoir is overflowing, it must be the slave since that is the only place where the fluid can cross over.

[jpflip]

Since a long time I am trying to understand the slave functioning. In the picture you can see an explosive view of the unit. I have found: the accumulator and power steering pressure goes to "Pressure A" of the piston. Which is a smaller area to push the piston. So remember accumulator and power steering pump work together. The larger area which is "pressure B" of the piston got his pressure from the pedal. I understand there is also "W" that I would like to call a pressure differiential control valve. The pressure acting on the spring relocate the plunger to supply fluid somewhere else (I did not clarified that one). Also X and W are also pressure relief valves and that is where I have found a possibility of migration since there was a weak o-ring on the X part. Also my thinking was a migration possibility between the two piston pressure area separated by big rubber rings (pressure A and pressure B part). but they were in good shape. I had to suspend my study of this unit because now I need another unserviceable unit to do some test without having it in pieces. So I have to wait for my valve to fail again :( Or if there is any volunteer to send me your u/s unit I will pay for the shipping since I am located in Montreal Canada....I don't know if this will take me anywhere but understanding a system can lead to a fix....