Clouded Brake Fluid

[Peter M.]

While checking the brake fluid level in my 1966 dual reservoir PB master cylinder with a flashlight, I noticed what looked like whitish clouds suspended in the standard DOT clear reddish brake fluid. One reservoir had more then the other but both were contaminated. The fluid is 2 years old and the brakes operate perfectly. Obviously I will replace the fluid --- Is this a common occurrence caused by water absorption?

[Jerry Clark]

Re: Clouded Brake Fluid

yes, unfortunately
jer

[Duke W.]

Re: Clouded Brake Fluid

Brake fluid tends to darken with time, but I'm not sure what causes it. I notice that front brake reservoirs darken faster, so it could be heat related. If the fluid has not been changed for a long time a fine sludge can also build up on the bottom of the resevoir. I think some of this might be tiny pieces or rubber that wear from the cups and other rubber parts.

I've seen test strips that you can dip into the fluid and its quality is indicated by test strip color. I recall the strips did not test for moisture, but something called "alpha contanimation", but there was no explanation what that is.

Changing the fluid every two years should go a long way toward adding longevity to your system.

Duke

[Jerry Clark]

Duke: "whitish clouds suspended"

sound like water to me.......no mention of Darkening
jerry

[Duke W.]

Re: Duke: "whitish clouds suspended"

I don't think it's water. I've mixed water with fresh brake fluid and it does not change the color. Also, water is miscible with conventional glycol brake fluid, so the water content is impossible to judge visually.

I can't come up with an explanation for the description, but it would be safe to assume that it's some kind of contamination, and a thorough system flush would be a prudent Rx.

I flush all my cars brake fluid every two years, and my basic rule for brake fluid quality is that if it is dark enough to not be able to see the bottom of the reservoir, it should be flushed, and the same would apply to anything that appears to be suspended in the fluid or a non uniform color.

Duke

[Jim T.]

Re: Clouded Brake Fluid

I have been using Castrol GTLMA brake fluid. The LMA is Low Moisture Activity according to the container. It is a mostly a clear color of brake fluid out of the container. It says that it exceeds DOT3 and DOT4 specifictions and made in USA. I read once where this brake fluid does not absorb moisture as easily as some others. I would think this could only mean when you remove the cover to check the fluid and absorbing less moisture from the air in a sealed system.