Intermittant clutch slip
06-15-2015, 09:36 AM
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Intermittant clutch slip
I am having issues with astrange intermittent clutch slip. Late last year I installed the 949 sport organic1.8 clutch after having the turbo on the car for 6 months running wastegateboost on the fairly new (<15k miles since 1.8 swap) Excedy clutch. I had noslipping issues on the Excedy before the clutch swap.
Some time after taking 1000miles to break the clutch in I would get slippage after fast 1-4thshifts. It would only do it every now and again. From past experience when aclutch lets go it will slip all the time, especially in higher gears when buildingboost. I can let the car cool down and go out and do the same fast gear changesor fully loaded in 4th and 5th with no slippage.
I have finally figured outthat the slippage is temperature dependent. If the car is cold (<30 minutesdriving) it never slips. If it I have been driving hard (no slipping at first)or it is real hot outside it will start slipping after driving it for a while.First I thought my speed shifting was contributing, but last week it startedslipping after cruising on the interstate for 10 minutes.
Searches found peoplehaving similar issues due to expansion of the clutch fluid causing someresidual pressure on the pressure plate that reduces the clutch clamping forceenough to cause slippage. This would make sense since I am only having thisissue when things heat up. I measured the temperature of the clutch line whereit crosses over the exhaust side and top of engine and it was round 190 deg inthe hottest places. Didn’t think that was that hot. I don’t know if this isreally happening since the master should have the port open to the reservoirwhen the pedal is all the way up so any fluid expansion should just go into thereservoir, not apply pressure to the clutch fork. I checked and the littlebreather hole in the reservoir cap is open so there is no pressure gettingtrapped in there either.
I have done 10+ clutchpedal adjustments to ensure there is enough free play at the top of the pedalstroke, but still fully disengaging when the pedal is fully depressed. Ibelieve the manual calls for ½” at the top of pedal. This apparently is toallow for any fluid expansion. I even have the pedal up cruise switch removedto give it a ton of free play at the top.
I re-used the Autozoneclutch slave and master that were replaced with the 1.8 swap and Excedy clutch.I did add a 949 braided clutch cable. I have bled the crap out of every fittingseveral times now. Going to try and make a pressure bleed fitting out of an oldreservoir cap just to make sure I get it all out.
Even after doing all this Ican still get the car on ramps after a hot/slipping drive and there is no freeplay on the clutch fork. It does have some pressure on it, not much (don’t knowhow much is needed to slip). I can easily push the fork back on the slavecylinder and it will push fluid out back into the reservoir.
I am starting to wonder ifI need a return spring or something on the clutch fork to take any pressure offthe release bearing when I am not stepping on the pedal.
Any ideas would be greatlyappreciated since I am very confused at this point!
Some time after taking 1000miles to break the clutch in I would get slippage after fast 1-4thshifts. It would only do it every now and again. From past experience when aclutch lets go it will slip all the time, especially in higher gears when buildingboost. I can let the car cool down and go out and do the same fast gear changesor fully loaded in 4th and 5th with no slippage.
I have finally figured outthat the slippage is temperature dependent. If the car is cold (<30 minutesdriving) it never slips. If it I have been driving hard (no slipping at first)or it is real hot outside it will start slipping after driving it for a while.First I thought my speed shifting was contributing, but last week it startedslipping after cruising on the interstate for 10 minutes.
Searches found peoplehaving similar issues due to expansion of the clutch fluid causing someresidual pressure on the pressure plate that reduces the clutch clamping forceenough to cause slippage. This would make sense since I am only having thisissue when things heat up. I measured the temperature of the clutch line whereit crosses over the exhaust side and top of engine and it was round 190 deg inthe hottest places. Didn’t think that was that hot. I don’t know if this isreally happening since the master should have the port open to the reservoirwhen the pedal is all the way up so any fluid expansion should just go into thereservoir, not apply pressure to the clutch fork. I checked and the littlebreather hole in the reservoir cap is open so there is no pressure gettingtrapped in there either.
I have done 10+ clutchpedal adjustments to ensure there is enough free play at the top of the pedalstroke, but still fully disengaging when the pedal is fully depressed. Ibelieve the manual calls for ½” at the top of pedal. This apparently is toallow for any fluid expansion. I even have the pedal up cruise switch removedto give it a ton of free play at the top.
I re-used the Autozoneclutch slave and master that were replaced with the 1.8 swap and Excedy clutch.I did add a 949 braided clutch cable. I have bled the crap out of every fittingseveral times now. Going to try and make a pressure bleed fitting out of an oldreservoir cap just to make sure I get it all out.
Even after doing all this Ican still get the car on ramps after a hot/slipping drive and there is no freeplay on the clutch fork. It does have some pressure on it, not much (don’t knowhow much is needed to slip). I can easily push the fork back on the slavecylinder and it will push fluid out back into the reservoir.
I am starting to wonder ifI need a return spring or something on the clutch fork to take any pressure offthe release bearing when I am not stepping on the pedal.
Any ideas would be greatlyappreciated since I am very confused at this point!
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