I have a 92 F150 M5od with concentric slave. A few weeks ago I had to replace the clutch becuase of slipping. After I put the truck back together everything seemed fine except for a slight pause and spring back at the end of travel when I let out the clutch. I drove for a few days then on a really cold day I had to double clutch the truck on my way home from work. I bleed the clutch and everything was good for the next week, then one day that was very cold again it got really bad, really fast but I checked and had not lost any fluid I double clutched and got home. Next day it was fine and I checked it a week later still no fluid loss and fine. Today on my way into work the clutch hung a little again but I didn't worry about it.
Leaving work just before I got to the freeway I hit the clutch in trafic and about 30 seconds later the truck started wanting to go so I turned it off and when trafic went I started it and got on the freeway. I made it till I got off to go home. I used the clutch once on the exit then had no clutch the next tiem I hit it for a light. I got out and got the truck off the road, looked and had no fluid. From what I could see there was no fluid anywhere on the master cylinder on line and I didn't see any extreame amount of fluid when I pulled the inspection cover on the bell housing. The inspection cover was dry from when I wiped it off when the tranny was out
and the inside of the housing only had the light oil/grime that I couldn't clean out.
So my question is, how do you test to find out if it is the master or slave leaking? I would really rather not have to pull the trany again but I dont' want to drop $50 that I don't need to on a master if thats not it.
One other thing I noticed is there is what looks like grease in my master cyl resuvour when I am bleeding the system.

 

Well on cold days the hydrualic clutch will be slow in repsonse not matter what. As for checking it I would get a buddy and have him push on the clutch pedal while you inspect the system. Some of these things are a pain in the **** to diagnose. All i can say is good luck man.... post what you find so if anything of this happens again we have a general idea of what it would be.

 

Well, I bled the system again really good and did not see any obvious leaks, of course I had fluid everywhere from bleeding it so I couldn't tell if there were any. My friend who is a mechanic drove my truck back to his shop while I followed and he said about half way the peddle started sticking down about half way up and not returning. I'm guessing that for some reason when I replaced the clutch the slave cylinder decided to go out. So now I'm pulling the tranny back out to change the slave. I also think that at first the slave was leaking a little but not enough to cause trouble very fast, That is why at first the peddle would hang just a little and spring up. Then when the slave got worse and started leaking more I ran the master cylinder down and now that needs to be replaced as well which may be indicated by the peddle now not returning past about half way. I hate to replace the master cylinder if it's not bad but most people have said you can mess up the seals when you run it dry, I'm guessing the seal leaking causes a lack of pressure allowing the peddle to stay half way down.

 

Well, I was half right. The clutch was leaking. The bad part is I pulled the trans again, put in a new slave, also put in a new master and inspected the line for any cracks. Put it all back together and after driving for about 10 minutes I hit the clutch to go around a corner and when I let out it didn't come with my foot. I used my toe to pull the peddle up and it went into gear just fine but after that almost every time it didn't come out. Most of the time at a stop it will act normal but almost never when I am already moving with the peddle come out. The slave came with the bearing and said it was pre greased when I bought it but after a few days of the clutch sticking I sprayed it very carfully with lithium grease to see if that would help but it didn't change things a bit.

I've had the trans out twice now, once for the clutch and once for the slave. The entire system is new but I am still having problems. Anyone have an idea of why the peddle would stick on a brand new master and slave clutch disk and pressure plate?