(1990 F-150 4x4 5-speed manual)

I completed a clutch job about a month ago and the truck ran smoothly for a few weeks. One morning I hopped in to drive to work and the clutch slave cylinder seal was blown. As it turns out this is a common problem and most folks recommend to replace the slave cylinder when putting in a new clutch (in this case we are talking about an internally mounted concentric slave cylinder).

So I learned my lesson, pulled the trans again, and replaced the slave cylinder (and the master cylinder while I was at it). I put it all back together and hooked it up to the hydraulic line. While I was attempting to bleed the system, the brand new slave cylinder started leaking like a sieve from the piston seal.

So now I am facing pulling the trans a THIRD time . I am trying to figure out what on earth I did wrong so that I don't do it again.

Here is my best theory, and I am seeking any more input on it:

Before installing the new slave cylinder I removed the bleed screw completely and the female quick connect and filled the cylinder with brake fluid, chasing the air out as much as possible (then reinstalled the bleed screw and quick connect). I slapped it on the bell housing and bolted the transmission to the engine block. At this point I did not connect it to the hydraulic line leading to the master cylinder for another two days!

1. Was the build-up in hydraulic pressure caused by the pressure plate pushing against the throwout bearing compounded by the fact that the pressure had nowhere to go for two days enough to ruin the new seal?

2. The new cylinder was aftermarket. Are they known to occassionally have faulty seals right out of the box?

3. I'm guessing not, but is the seal itself replaceable in these concentric slave cylinders?

4. What else could I have done wrong?

 

I half the same exact problem with mine when i did it. I found burrs on the end of the hydraulic hose, and they were not allowing the seal on the slave to do its job. I replaced the hose (like $45-from o'reillys) and everything went together great. You could try taking emery cloth or something to it, and maybe get it to go.. its worth a try rather than pulling the tranny again, hope this helps.

 

Where are you buying the slave cylinders from?

 

I had the same problem and on the third exchange of a new leaky one for a temporarily not leaky one I finally gave up and went to a Ford Dealer, bent over, and paid premium dollar for the motorcraft part.

And... it doesn't leak.

Considering I pulled the tranny off four times total, I should have just bought the motorcraft part in the first place.

Hindsight is 20/20.

 

rocketfootballer: the new slave is definitely leaking from the piston seal and not the hose connector, I can see fluid running out of the throwout bearing whenever the clutch is depressed.

Bought the new slave from NAPA. I just picked up another new one today from O'Reilly under the assumption that NAPA won't take back the leaky slave (I have to assume I did something wrong) and I saved $10 on it.

That is NOT what I wanted to hear frederic, but thanks for the input. I'm hoping I have better luck with the second one.

 

There's not much you could do wrong that would wreck it. I'd forget the NAPA and the O'Reilly and get a genuine Ford. Unless you enjoy R&Ring the the trans.etc.

 

I did my clutch and throw-out last summer ( summer being the key word )-bought them from the local NAPA -- have had no problem--but my life is good all the time !!!
I can fall in a bucket of...well you know..

Gary

 

Installed the O'Reilly part and everything is fine. I'm sure there is nothing wrong in general with the NAPA part, just got unlucky I think and got a faulty seal right out of the box.

 

After you have to change it every 6 months you might change your opinion about that. What I don't understand is that you have a motorcraft part that last for 20 years... why would you switch to a different brand to save a few bucks? I guess you don't mind the work of pulling your transmission.

 

huh...i just did the slave on my truck this past weekend and got all of my parts from NAPA...i mite be checking mine out in a weeks time to make sure the same hasnt happened to mine....as of now mine is good.

 

Anyone heard of reliability issues with these concentric slave cylinders? I've had a '96 302 4X4 5-speed F150 for about 10 years and have replaced about half a dozen of these hydraulic wonders. All were OEM, from Ford and typically last me about a year and a half. After paying Aamco, Ford and the local mechanic to replace them I've taken to doing it myself. I've never had a recurring problem with any other component of the clutch assembly, just the friggin' piston seal on the slave cylinder. I milked the last one (just got it back together this afternoon) for a couple of months. I noticed that it leaked like a sieve on cold days (40 degrees and lower) but was fine once the engine got everything warmed up. Warm days it was firm and wouldn't leak a drop. Anyone have a suggestion as to what I can try to extend the life of this one?

 

Is there oil in your fluid reservoir? Oil will eat the seals if it gets into the fluid.

Get a turkey baster and suck some of the fluid out. Put it in a jar and add water. Shake it and look for separation. If there is any oil you will see it.

 

If anyone knows how I could convert to a mechanical clutch, please let me know. I'll be all over it. An external slave would be a suitable alternative. I love my truck and I don't drive it hard. It's been very reliable and relatively trouble free. Except for this hydraulic clutch. It's hard for me to imagine oil contamination, especially since the reservoir is mounted on the firewall, away from everything but the brake reservoir. Water? Maybe... but, the cap seals tight, isn't cracked, the seal is good and I don't open it very often to check it... that kind of limits the opportunity for anything to get in there. It's pretty clean under the hood so, I don't think dirt is getting in there. And it's all fairly new. About 3 years ago, I replaced the entire hydraulic system (master cylinder, reservoir, line and slave cylinder) using new Ford parts. One evening, about a year after that, the slave cylinder just came apart while I was driving down the street from my house. I didn't have the time to fool with it so I farmed it out to a repair shop. They said the piston pushed out of the bore. The one they installed looks like a decent quality aftermarket but the basic issue appears to be the same. Seal failure. The bottom lip of the outer seal retainer ring is rusted from the leaking clutch fluid. My problem is, by the time I know something is wrong, it's too late to troubleshoot it. I'm either already calling a tow truck or I'm having to prepare to replace it. The reservoir is too small to retain contaminated fluid once there's a leak so, the evidence is hard to come by. I've gotten over 150,000 miles out of mechanical clutches in other vehicles, vehicles that I drove abusively, I might add and I baby this thing. What the heck could I be doing wrong? Like I said, this is extremely frustrating for me. I done this enough times I could talk a 5 year old through it over the phone. About the only thing I haven't tried is using only Ford ESA M6C25A. I've been using Prestone synthetic DOT 3. Maybe I'll flush it this weekend and go with Ford fluid.
Thanks for your reply Andy. You made me consider other possibilities.

 

duplicate msg

 

I'v had this issue too, the first 3 time i changed the clutch i had to go back and replace some part of the hydraulic system, the 1st time had to go back and get the slave, the 2nd was the master and the 3rd the slave, master and line.

At first i thought that the seal failure had something to do with the heat built up when the clutch was getting old and slipping. But now after reading all of this there has to be another issue.

the last time i did the clutch was 1 1/2 ago. An oreillys slave and it already shows signs of seeping fluid. But I think youll have just as much luck with a parts store as with the dealer. At least oreillys give you a free replacement.