Bought a new Wagner master cylinder for my truck and no surprise it’s made in China. I decided to pull the pistons out and have a look at the quality of the components which didn’t look too bad, but there was fair amount of some type of assembly fluid (oil?) in the bore. It was pretty viscous, sort of like STP. Mineral spirits cut it like it was oil. Any idea what this stuff is? I always heard brake fluid and oil don’t like each other.
Master cylinder assembly fluid/oil?
- Thread starter LG63
- Start date
Tim The Tool Man
Well-known member
Not an expert but I would guess they used straight break fluid or possibly some type of silicone lubrication.
Certainly can't hurt in cleaning the components with non-chlorinated brake 
parts cleaner and re-assemble. At our shop, we simply inspect a reman master cylinders before bench bleeding but none of the techs ever complained about seeing a heavy oil type of fluid in them. A bench bleed before installing would flush out any material.
parts cleaner and re-assemble. At our shop, we simply inspect a reman master cylinders before bench bleeding but none of the techs ever complained about seeing a heavy oil type of fluid in them. A bench bleed before installing would flush out any material.It is an assembly fluid. Years ago when rebuilding cylinders was much more common, most brake manufacturer's offered an assembly fluid. In recent years, I have not seen it and myself, just use DOT 3 brake fluid.
As mentioned, I would also suggest cleaning everything up with brake cleaner and blow dry with compressed air.
Tim
As mentioned, I would also suggest cleaning everything up with brake cleaner and blow dry with compressed air.
Tim
LG63 why did you buy new only to take it apart and remove the mfg. assembly product?
What did you relube with? Obviously the mfg wanted that product where they put since it cost them money to do it.
So I would now be suspect of your "new improved version" ....if you don't trust their product then you should have looked at another mfg that you do trust.
No doubt in my mind that the product was supposed to be there for proper assembly and operation.
What did you relube with? Obviously the mfg wanted that product where they put since it cost them money to do it.
So I would now be suspect of your "new improved version" ....if you don't trust their product then you should have looked at another mfg that you do trust.
No doubt in my mind that the product was supposed to be there for proper assembly and operation.
c39er
Well-known member
It's an assembly lube for brake hydraulic brake parts. I have a small bottle of it.
454ragtop
Well-known member
Raybestos makes or made brake assembly fluid. I still have a bottle, night and day difference versus brake fluid for assembling calipers, lot slipperier (is that even a word?). I would just put it back together, no need to clean it out.
Jim
Jim
Kevin C
Well-known member
"For lubricating hydraulic components, such as the piston seals inside calipers and wheel cylinders, you can use a silicone-based brake lubricant or ordinary brake fluid. This type of lubricant will help assure smooth movement of the seals in their bores, and will help prevent these parts from sticking or corroding."
http://www.brakeandfrontend.com/issue/article.aspx?contentid=38625
http://forums.rennlist.com/rennforums/993-forum/510131-brake-piston-seal-grease.html
Might be silicone.... I always had a bottle of brake assembly lube but I never looked to see what it was. Seemed to help prevent corrosion and scoring.
http://www.brakeandfrontend.com/issue/article.aspx?contentid=38625
http://forums.rennlist.com/rennforums/993-forum/510131-brake-piston-seal-grease.html
Might be silicone.... I always had a bottle of brake assembly lube but I never looked to see what it was. Seemed to help prevent corrosion and scoring.