M151A2 master cylinder plunger - it's stuck

[Maple Leaf Eh]

Fellow M151A2 owners' suggestions sought.

My A2 went off the road in 2018 with an obnoxious engine knock. I got busy with an estate, had some more important life business to get through, the lockdowns started, and the Jeep didn't go into rebuild until 2021. My builder did a full body strip and repaired lots of bad sheet metal. The mechanicals were removed and reinstalled, except for a tested Take Off motor. The brakes before the build were pretty snappy! However, since June 2024 when I got it back, the brake pedal has nearly no resistance.

I tried bleeding the lines, but the plunger on the master seems to be stuck in. My builder had the Devil's own time reinstalling the pedal and master assembly, and he's extremely reluctant to get into it again. (He's bigger than me and neither of us have small arms or hands, not to mention we're not circus contortionists. And this was his last build - ever.)

What fixes (and I have the TMs) might I consider to move the plunger - without disassembling the installation? Can the plunger be moved from the footwell?

 

[glcaines]

If your A2 had ROPS installed, the light switch was moved over. If you remove the light switch, you have better access to the bolts for the MC. Just follow the TM to remove the master cylinder, I did it and it wasn't that difficult and I also have large hands. I replaced my MC with an NOS one and all of my problems disappeared, and it wasn't that expensive. However, one thing to remember is that there are two different copper washers and they need to be replaced. They are a different size and it is important to get the correct ones or you will have leaks. Another note is that the NOS MC I purchased had a very cheap cap on it that didn't have a vent hole, so save the one from your old MC which is likely better. Make sure you use the correct brake fluid. DOT 5 is not compatible with DOT 3 or 4 or 5A.

 

[Maple Leaf Eh]

Hmmm? You've made me think, and some days that's a bad thing. If the light switch can help access the left side, would opening the instrument panel and tilting it forward help access the right side?

 

[glcaines]

Not sure if it would help. I didn't do it. Removing he light switch only helps if ROPS was installed and the light switch was relocated to the right. The TM is actually very good at describing the process of switching the MC, but doesn't mention the part about the light switch. Be careful of sharp metal when switching the MC. I had several cuts on my hands from the process.

 

[foxmike]

I recently replaced the MC with a NOS one as well. Removing the light switch helped a lot.
There is a caution about bench bleeding the new MS. Don't bottom out the plunger.