Contaminated brake fluid?

[mybigtruck]

In another thread, I outlined a problem I am having with my brakes. In the course of looking around, I have come to suspect that I may have contaminated brake fluid. What is best way to be sure that it is? I don't want to have to start replacing all of the stuff I will have to replace until I am absolutely sure.

[Sabaka454]

contaminated with what? Flush the system.

[Bandit130]

Inspect fluid in MC front and rear reservoir. If there is a definite discoloration, may be contaminated. I had this 2 years ago when I purchased my 74. Rear was contaminated, green looking fluid. Replaced MC, rear cylinders, flushed lines, all is well since. Not saying yours is, but worth inspecting.

[mybigtruck]

It is discolored and and cap gasket is swollen and deformed. I am almost certain it is contaminated but I am wondering if there is any way to check further.
If it is, what do you guys think is the best course. there is so much rubber (seals, hoses etc.) in a brake system that I think I will have to replace the MC, flex lines, calipers, wheel cylinders, any thing with rubber. Are there rubber seals in the proportioning valve?

[wilkin250r]

Contaminated brake fluid doesn't necessarily mean you need to change the rubber. It might just have absorbed too much water over the years.

I had a similar problem with a motorcycle. I think the brake fluid just absorbed too much water, lowering the boiling point. When the system developed any heat, the fluid would expand, which caused pressure, which caused the brakes to drag, which caused more heat, which caused more pressure... until the rear brakes essentially locked up.

I never had to replace the rubber, I just flushed the system, and it functioned perfectly after that.

(of course, replacing aged rubber lines might not be a bad idea anyways)

[mybigtruck]

It is discolored and and cap gasket is swollen and deformed. I am almost certain it is contaminated but I am wondering if there is any way to check further.
If it is, what do you guys think is the best course. there is so much rubber (seals, hoses etc.) in a brake system that I think I will have to replace the MC, flex lines, calipers, wheel cylinders, any thing with rubber. Are there rubber seals in the proportioning valve?

[Killer Bee]

brake fluid is hygroscopic

the absorbed water causes oxidation and changes color as well as affecting compressibility..

should also verify compatible type of brake fluid for the system..

might want to consider total flush and replace all elastomers [soft parts] or components with them inside..

decent article should clear things up a little..

What You Should Know About Brake Fluid

make no compromises in your brake system please..

not only your life but your passengers lives and the lives of other motorists depends on it!

good luck!