...of the clutch master cylinder? I'm beginning to wonder if this is my problem of my "clutch pedal with mind of its own" syndrome. For those of you who don't know the details, I replaced my OE clutch with an ACT street modified clutch. I'm having trouble with the clutch pedal wanting to move itself's engagement point and freeplay. One minute it will be perfect, then the next minute it will be hard as a rock with the engagement point 1/2" from the top of the pedal travel.

I think I have come up with a pattern. I had my car parked for a while tonight and it was cold. When I got into my car the clutch had alot of freeplay and was pretty loose. I remember when the clutch gets hard it usually after some prolonged idling, like in the Taco Bell drive thru line last night.

I think water may have contamnated my brake fluid, although it was just bled. It may make sense too, cause as the brake fluid in the slave system in the engine bay heated up, this caused volumetric expansion, which in turn caused my clutch pedal to become hard. When it was cold, the opposite happened and it softened up. From my understanding, brake fluid is supposed to resist expansion/contraction due to temperature, and the presense of water certainly compromised this. The automatic adjuster on the clutch was probably confused like crazy too.

How did the water enter my freshly bled clutch system? Perhaps since I washed out the engine bay after I bled the clutch to clean the brake fluid the water got into the hydraulic system, and I know brake fluid absorbs moisture. This plus the automatic self adjusting mechanism is probably causing my clutch to act all funny. Does this sound possible or am I way off?

 

water is bad...the reason brake fluid works is because it is uncompressable....i believe that water wont do nearly as good a job.

 

Water, like any liquid, is not compressable. The problem is that water causes rust and a rusty (read weakened) brake system ain't good. The second problem is that water boils faster than brake fluid. Boiling water is a gas, gas is compressable, making the brake spongy, which ain't good.

 

oh, yea thats it, hehe, its been a while since chem

 

What does brake fluid have to do with the clutch?

 

Bert is right. Just water compresses just like any liquid. If you have a spongy clutch pedal only at certain times, I don't think you can blame the water. If the lowered boiling point is going to cause air pockets, you'd think that the pedal would be soft all the time. Moreover, only by an act of sabotage could significant amts of water get into your clutch/brake system, don't you think?

 

The hydraulic clutch uses brake fluid too.

Water could get in to the system if the seal on the reservoir isn't perfect and was hit with a high pressure spray when you cleaned the engine compartment. Just bleed it again, won't even take you 1/2 hour. If your problem goes away, great, if not, you at least eliminated one possible problem. Good luck.

 

Alright well obviously the hydraulics of a clutch system will never get as hot as brakes will. I dont know what temp the engine compartment gets (yet) but I can imagine at idle even with the fans running it gets around 220 degrees or so. At least this is a guess, cause my motorcycle has a digi water temp gauge and it gets to 220 degrees before the fans turn on.

I bought an indoor/outdoor thermometer from Radio Shack today that has a remote lead. I will use this to monitor under the hood temp (or intake temp, or amplifier temp in the future). Then hopefully I can put a more reliable pattern on my problem.

Although the water boiling point is low, the expansion point is probably what is at fault. Just think- whats that coolant overflow reservour for? So far, it seems after the car has been sitting a while, the clutch has alot of freeplay. This makes sense, because the fluid isnt expanded. When the engine compartment is hot, and it heated the fluid enough, the fluid is expanded, thereby giving the clutch the hard feel and the raising of the engagement point. The fluid would not be hot enough to boil unless it got really ungodly hot under there.

I'll put in the probe and monitor its activity to have solid numbers. Hopefully just bleeding the thing out will cure the problem. Or who knows, maybe in time the water will eventually work its way out of the system...assuming its water that caused the problem.

 

I agree, it shouldn't be a problem with it boiling. The water will not work it's way out of the system by itself if it's sealed properly though. You'll have to exchange the fluid.

 

it also lowers the boiling point of the fluid, making the vehicle fade once the temperature goes beyond the boiling point. this is why manufacturers list both wet and dry boiling points of their brake fluid.