Bewildered about slave cylinder

[gw33gp]

Since I did a clutch replacement about 1-1/2 years ago, I have to bleed the slave about every two weeks. I used a LUK clutch (self adjusting) like I always use, but decided to use a Sachs slave because it has the rubber boot on it and the LUK does not. On Rock Auto the Sachs slave description is non-self adjusting. I don't now what that means because that is a term for the clutch. After about two weeks the clutch engagement started with the pedal very near the floor. After bleeding it engages about 1-1/2" from the floor. I like it a little higher, but that still works for me. That continued on with needing to bleed about every couple weeks.

Then last year I went on a four week off-road trip on the Continental Divide Trail. As I was driving to New Mexico I realized my clutch needed to be bled again. I ended up forgetting to do it and realized at the end of the trip and on my way home, my clutch was working better than ever without have to bleed it. Later, I had to replace my transmission because it started popping out of 5th gear. After the install, the two week bleed need stated again. I just accepted it and bled it when needed.

About a month ago I went on an off-road trip on the Arizona Peace Trail. During the trip the clutch started engaging with the clutch pedal around 2" from the floor, which is near where I like it. I thought the bleed issue was gone. Then this weekend, it came back.

I can usually figure out mechanical problems and have been pretty lucky with slave cylinders over the 22 years and 272K miles that I have owned this Ranger. I have done a clutch job a couple times with no issues. I have just given into having to bleed every two weeks but am baffled as to how air gets into the slave.

It seems to happen overnight. I always notice it needs to be bled in the morning when I start it for the first time that day. I have thought that maybe when the clutch pressure plate cools overnight, it may cause the slave to pull forward due the the spring action on it. However, I think the fluid would flow in from the master cylinder before it would draw air in from around the seal in the slave. I am not going to go back in and replace the slave, but I am just curious. What else could cause this problem?

 

[superj]

crazy. for me, thats always some kind of leak. maybe at the bleeder valve seat

 

[Uncle Gump]

Do you actually bleed air out?

I've never seen air enter a hydraulic system without fluid being able to escape.

The only thing that makes sense would be the none pressure part of the system (reservoir/fill hose). A small air leak that happens between operating temp and cool down allow a tiny bit of air into the compensating port of the master. But it's only a guess.

 

[Shran]

That's weird... I wonder if there is a bad seal somewhere? Master cylinder perhaps, at the push rod or where the hose goes into the master cylinder? You'd think it would leak fluid somewhere.

 

[rubydist]

I had a slave cylinder on my 03 that would let air in sometimes. I don't know if it was the cylinder itself or the connector to the slave cylinder, but replacing the thing fixed it. I hate bleeding those things - the way they are designed makes it really difficult to bleed. I finally bought the pre-bled master and slave parts, and once I installed those I had no more problems.

 

[gw33gp]

I have no leak. I only have to add a little fluid when I bleed it. I have ruled out the master cylinder because bleeding the slave fixes the issue for a couple weeks. Yes, I do get a little air out on the first cycle of bleeding. I always do a second cycle just to be sure and no more air comes out then. I am pretty sure the problem is in the slave or the connector to the slave. The bleeder valve could be the culprit also but I do always snug it up.

Gravity should overcome air from getting into the brake hydraulic system. I have done gravity bleeding on vehicles before successfully without getting air coming in.

I have gotten very good at bleeding it and can do it quickly. My Ranger sits up high enough that I have easy access to crawl under it. I have a stick that I use to hold the clutch pedal all the way down while bleeding. I usually use a tube to direct the fluid into a container while bleeding. However, I have also done it without a tube when I am not home.

The thing that really has me perplexed is how it fixes itself when on long trips. It seems letting it sit for a few days brings on the problem.

Thanks everyone for you ideas. I will let you know if I ever figure it out. I think replacing the slave cylinder would fix it but I am not doing that unless it starts leaking.