Novak Conversions Jeep Wrangler YJ shifters

Master Slave Cylinder Assembly Issues

952.5YJ

New Member
Joined
May 8, 2025
Messages
6
Location
Virginia
On my 95 2.5 the original 30 year old clutch master cylinder started to leak a few days ago, I replaced it with a pre bled Duralast master-slave full assembly and it started leaking at the master a few miles later. I replaced that with a Doorman pre bled full assembly and that one lasted a few miles and then the pedal dropped to the floor with no external fluid leaks and the fluid pushed all of the way up against the cap making it hard to take off to inspect. I know there has been a lot of trouble with the after market ones, has anyone had any experience with them failing pretty instantly? Peaking in the bell housing the fork seems aligned ok and the pedal felt great for the first few miles on each part before it died. I replaced one on my other 95 8 years ago with a Mopar one before they discontinued them in 2020 and it hasn’t had any issues. I am just suspicious of these last two parts and was wondering if anyone had experience like this and if there is anything else to check. Thanks!
 
That is a frustrating issue. I haven't used Dorman or Duralast but I have used the PowerTorque one that Oreilly sells and I had to replace them about once a year under warranty. On the third one the pedal got stuck at the floor.

I bought a "Mopar" (not sure if it was really Mopar and installed it in 2017, but I haven't put hardly any miles on it since then, so it's hard to say if it's really fixed or not.

I would try the O'Reilly one or maybe one from RockAuto just to see if it can fix the issue for longer than 5 miles.
 
I ordered a Carquest one off RockAuto. Hopefully third time’s a charm. When I installed the last two I had to push the piston on the slave cylinder in some against the fork cup to get the bolts in. Really they are studs but the nuts are stuck on them. I think it was like that on the one I did before 8 years ago, I just work it down evenly one at a time until it is seated.
 
Having to push down is normal, there is a spring inside the slave cylinder which is what maintains constant pressure on the throwout bearing so that it rides the pressure plate consistently and the bearing face doesn't skip on the pressure plate fingers.

A lot of people think the bearing pulls away from the pressure plate at rest, but nope, it is in full contact with the pressure plate at all times.
 
I put the one from Rock Auto in today it had the normal push down that you mentioned but the straps are not snapping off on this unit, I had a friend push on the clutch pedal so I could watch, the t comes up to the flange on the straps but is just shy of enough force to snap them off. Also the boot on the master cylinder at the inside of the firewall keeps sliding off and riding on the push rod. The other two actually had that as well I was going to address that with some rtv silicone. All 3 of these brands have different stamped part numbers in the cylinders but in the same spot and look identical. I think it is all one manufacturer.
 
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It was driving ok with the third assembly but the pedal felt like it was sticking a couple of times. One thing I noticed from the original one is the rubber boot around the master cylinder has several vent holes the new one only has one tiny hole. I am wondering if vacuum may be holding the pushrod in. I also hear a clicking sound now coming from the push rod with the pedal almost all of the way in.
 
Just an update. I have been driving with no issues the last few days with no issues with the PF9002 from Rock Auto. I did have the clutch pedal stick down a couple of times the first few miles but it came back up slowly and has been fine since also the noise at the pushrod went away. If anyone needs a new master/slave I think this is the one to buy now it looks identical to the other two but it was cheaper and works.
 
Novak Conversions Jeep Wrangler YJ shifters