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Clutch fluid migration...


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I know you talk about it in the past but no firm answer....My clutch expansion tank in front is always overfilled after an hour drive. Some of you are suggesting in previous post (here or 6speed) to replace the clutch slave cylinder other are talking about the accumulator or even both. As per repair manual there is a test to do for the accumulator which is: 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 −arrow− faulty and must be

replaced!

I did it on my car and no difference even after 100 depressions of the pedal. Can you check on your car if this test is valid and let me know. Because I don't understand why a faulty accumulator can cause fluid migration. To me an accumulator is an inline reservoir who provide a sudden surge protection on the hydraulic system or extra fluid under pressure (bladder type)in case of hydraulic system failure . At least on the aircraft that I am working on...

Let me know how you fix it....And were to purchase those parts...

Thanks for your help, info and replied, J.P.

996 116 237 52 slave cylinder

996 314 166 00 accumulator (nil pelican parts ???)

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Actually you can test it quite easily...no need for 100 presses. Leave the key off...depress the clutch about 20 times and it should become a bit stiff....but not really hard. It sounds like youre expecting it to become very stiff. Then start the car and wait about two seconds, then depress the clutch....it should feel very light and easy to depress.....if it does feel light...your accumulator is working.

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I know you talk about it in the past but no firm answer....My clutch expansion tank in front is always overfilled after an hour drive. Some of you are suggesting in previous post (here or 6speed) to replace the clutch slave cylinder other are talking about the accumulator or even both. As per repair manual there is a test to do for the accumulator which is: 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 −arrow− faulty and must be

replaced!

I did it on my car and no difference even after 100 depressions of the pedal. Can you check on your car if this test is valid and let me know. Because I don't understand why a faulty accumulator can cause fluid migration. To me an accumulator is an inline reservoir who provide a sudden surge protection on the hydraulic system or extra fluid under pressure (bladder type)in case of hydraulic system failure . At least on the aircraft that I am working on...

Let me know how you fix it....And were to purchase those parts...

Thanks for your help, info and replied, J.P.

996 116 237 52 slave cylinder

996 314 166 00 accumulator (nil pelican parts ???)

I sort of had the same problem... I noticed small drops of fluid on the ground behind my front driver side wheel. Took it to porsche and they said that the clutch fluid reservoir was over filled, no biggie, empty fluid out, clean up the mess, and sent me home. A day later, more spots on the ground. Took it back to them and then they discovered that the fluid was leaking out from another area and over filling the clutch reservoir which caused the whole system to over pressurize. They ened up having to replace the master cylinders or the acumulator (can't remember exactly, I'd have to look at my paperwork) for the clutch, brakes and someting inside the steering... ended up costing over $2,000... thank God for Warranty... $50.00 deductible

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To test the accumulator you want to run the car for a few minutes to let the accumulator build up pressure. Then shut the car off and depress the clutch pedal, counting how many times until the pedal becomes noticeably stiffer. If it takes less than 15-20 to feel stiff then the accumulator is likely faulty. The main symptom of a faulty accumulator is coming out to the car after a few hours and going to depress the clutch pedal when you start the engine and having the pedal feel rock hard. The normal feeling of the 996 turbo clutch pedal is extremely light, without the boost from the power steering pump the pedal is ridiculously stiff. The accumulator retains pressure and gives you hydraulic assist even when the engine is off, but only for approx 20 pumps of the pedal. If you can press the clutch pedal 100 times after the engine is off and have it feel the same, you definitely have a problem. The most common problem of a clutch pedal that doesn't feel right when depressing it is the accumulator. The clutch fluid over flowing the front reservoir is a different issue however. This is almost always a problem with the slave cylinder. The slave is what connects the two parts of the clutch fluid circuit. You're right on the accumulator not making sense in causing this, there is a valve that fails inside the slave and allows pressurized clutch fluid up and up into the front reservoir. It sounds like you might need both though! Make sure you buy a few cans of pentosin to bleed the system.

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If you can operate the pedal 100 times and feel no change I would say your accumulator isn't working at all. I understand the purpose of the accumulator is to provide a reserve of pressure when the engine is off to assist clutch operation.

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Just order Pentosin + accumulator + slave cylinder. I will let you know what fix it . I will also dismantle (or cut in half) the accumulator and the slave cylinder to exactly found out were there is a possibility of oil migration and what can cause this failure (o-ring wear or cylinder corrosion or bypass valve failure...). Give me a month before I found the time to crawl under my car and start working on it. Thanks for your info Wvicary.

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had the same issue on 993tt and it was definately the slave cylinder!!! the accumulator would give you a hard pedal if defective,especially on the first few pushes after switching off. what happens is the pressure built up by the pump is being allowed into the clutch line and thus causing the resevoir to seem overfilled. change the slave cylinder and bleed....job done! however as the accumulator is screwed onto the slave if you have the money it makes sense to change at same time.

WARNING!!! MAKE SURE YOU PUMP THE CLUTCH PEDAL AROUND 25 TIMES TO DEPRESSURISE THE SYSTEM BEFORE TRYING TO UNSCREW THE ACCUMULATOR!!!!

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  • 2 weeks later...
Thanks a lot Topmech0 for your help. I am still waiting for the parts and anxious to start working on it. There will be a feedback on my final result. Thanks again, J.P.

Do you have experience with replacing the slave cylinder on a 996TT? I ask because I will be removing the accumulator and slave cylinder on my 996TT to replace the accumulator and lubricate the slave cylinder actuator rod (squeaks due to lack of lubrication). If you have found instructions for this procedure, it would be helpful. In searching, I found instructions for a 996 non-turbo, but the slave cylinder on those is quite different compared to the TT. Thanks in advance!

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If you look on 6speed you will found a post by Mikelly. He is doing the job right now...http://www.6speedonline.com/forums/996turbo-gt2/137426-clutch-slave-replacement-need-answer.html.

Myself I just received the parts today so I will soon start this job. You don't have the repair manual for the TT ?

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Just to give you a start I was told you need a 27 mm open end for the accumulator and a 13 mm crow foot can be helpful for the most aft hydraulic line. Also a special tool is needed for the quick disconnect hyd line . The one with the red collar. Just do a Google search for fuel/ac disconnect tool....Good luck and please keep me inform of your struggle !

Edited by jpflip
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