Clutch Pedal Pressure Building While I Drive

[RidgeRacer]

I have a 2001 5-speed Pathfinder.

I replaced a piece of the clutch plumbing a few months ago (can't remember what it's called, but it has a piece of heat-shield looking material on it).

Since then, even though I have bled the system several times - it seems like maybe there is air getting in the lines somewhere. The reason I think that is because if the truck has been sitting overnight, the clutch pedal pressure is normal. The clutch engages in the range where I set it at first, but if I drive a lot and shift a lot, the engagement point moves up and up so that after a few hours of driving it will eventually act like the clutch is slipping.

But then, I can park it overnight or let it sit a couple of days and there is no fluid on the garage floor, it doesn't appear that the master cylinder level has dropped - and the pedal will go back to normal again - until I take it for a long drive, and it will build pressure again.

What could cause this? Maybe a bad master or slave cylinder?

Thank you!
Modified by RidgeRacer at 3:16 PM 12/27/2009

[Fisherdude]

could be a bad connection on the slave cylinder... one of these problems could F you in the A one day like it did with me. Let your mechanic look at it before you get stranded somewhere unable to shift your car..

[RidgeRacer]

OK - so I replaced both the master and slave cylinders. Figured I'd do them both - hoping that it would fix the problem.

After driving the car around for a full day after replacing them, I could tell that the engagement point was getting earlier and earlier in the clutch pedal travel toward the end of the day, like it was doing before. It didn't seem to happen as quickly or as much - but it was noticeable.

I noticed that when I removed the old master cylinder, it was almost out of fluid. I haven't seen any fluid on the garage floor though... WTF?

It makes sense that if there's a leak somewhere letting air in (and presumably fluid out), that the pressure would increase like that. But why am I not seeing any fluid on the floor? Is it possible that it's only leaking when it gets hot? If so - how can I track down the leak?

[Fisherdude]

while in your clean driveway pump your clutch about 30 to 50 times and check to see if there's fluid in the driveway, then do the same test when the car is warmed up. could help narrow down the problem.

[Chuck Tribolet]

RidgeRacer: I'd be looking real hard at the ends of the thiing you replaced.And where is it and why did you replace it?

Chuck

[RidgeRacer]

Yeah - that makes sense... Maybe a bad connection.

The whole thing started when I had to replace a connector piece that goes between the slave cylinder and the hard clutch line. I'm not sure what it's called, but it's flexible and has a piece of silver heat-shield looking stuff around it.

After that job, the pressure building thing started. I couldn't find a leak and searched the forums and got the idea that maybe I needed to replace one or both of the cylinders, so that's why I did that.

I'll try the clutch pumping thing in the garage and see if maybe the connection to that flexible line is the culprit.