Grease and brake fluid?

[eaglescout526]

So I went to AMC salvage today and got a few things. Of the few things was two clutch masters. One a Nabco(OEM) and the other is three circles to form a triangle. Anyways upon inspection of the Nabco one I found dried up brown grease on the plunger side closest to the cylinder. My question is, is there a chemical property between the two where the grease acts as a gasket?

 

Pic for what I'm talking about:

 

What is your thoughts about the idea? And I haven't seen anything in the FSM on this when rebuilding these. 

[Chad R]

I would think so. The pressure in the cylinder would blow it out when pushing it in. The rubber cup seal is the only thing that seals it. No different than a brake master cylinder.  Seeing that the clutch master cylinder uses brake fluid I would not even want to put grease anywhere near it. If I did grease it I would use a ceramic brake grease so it would not harm the rubber seals .

[eaglescout526]

1 hour ago, Chad R said:

I would think so. The pressure in the cylinder would blow it out when pushing it in. The rubber cup seal is the only thing that seals it. No different than a brake master cylinder.  Seeing that the clutch master cylinder uses brake fluid I would not even want to put grease anywhere near it. If I did grease it I would use a ceramic brake grease so it would not harm the rubber seals .

Youre probably right. I dug deeper into the FMS past the I.S.'s and found the newer (Nabco) master cyls and they show that a rebuild kit comes with some sort of lube for the ball of the piston. I will probably try the ceramic grease and rebuild one of the two or use the grease on my current one to prevent pressure loss and leakage. That's my main issue is pressure loss if the pedal is let up completely.

 

So my next question is what grease is brown or dries up and turns brown?

[Chad R]

My best guess is it’s some type of moly grease 

[Warren Mohler]

1 hour ago, eaglescout526 said:

 

So my next question is what grease is brown or dries up and turns brown?

Its a mix of the original grease and brake fluid

[eaglescout526]

So after about of month of rigorous research and diving into my vast library(more looking at the FSM) I found out that the clutch rebuild kits used to come with a grease for the rubber and outside shaft. The Crown rebuild kits fail to come with anything(shocker) because Crown auto. After searching for any properties between the grease and brake fluid I stumbled upon this:

http://www.redrubbergrease.com/clutch-master-cylinder-repair-leak-or-failure-with-rebuild-kit.html

 

I was skeptical of using this but figured, if it stops the leaking, I can live with it. So I got some and rebuilt the Nabco master I got and that one was in much better shape than my original master and the crown one was alright but it leaked ever slightly.

So far so good, I can completely let up on the pedal and still have pressure behind the push of the pedal when shifting. Fluid still sits in the master and it isn't black from the rubber of the plunger, more of a red tint from the grease but it performs really well.

So I think this mystery can be considered solved. 

 

Also performed an experiment with brake fluid and lithium grease and found the grease slows brake fluid travel when passing through it.