Brake fluid

OldFoggey · #1 (**permalink**) 03-06-2014, 08:09 PM

My brake lights aren't coming on and I've troubleshot it to the pressure switch on the master cylinder. Figuring that I would have to replace some brake fluid when I swap the switch I looked in the manual to see which fluid I need to use. The manual says DOT5 is required. I bought a bottle of DOT5 fluid but I noticed that my brake fluid is clear. Federal standards require that DOT5 brake fluid be purple in color. My car is build #889 built in 2010. Did my car get the wrong fluid put in it or is the DOT5 requirement not correct?

Thanks.....Don

patrickt · #2 (**permalink**) 03-07-2014, 06:12 AM

Quote:

Originally Posted by OldFoggey

Federal standards require that DOT5 brake fluid be purple in color. My car is build #889 built in 2010. Did my car get the wrong fluid put in it or is the DOT5 requirement not correct?

You can't rely on the color -- depending on how long the fluid has been in there it can change. Obviously I don't know what you have in there, but DOT-5 is oil based and it won't mix with DOT-3/4 or water. DOT-3/4 will mix with water, but not oil. So....

I would syphon some of the fluid out and then mix it with a DOT-3 sample in a nice clean mayonnaise jar. If they don't mix, then it's looking like DOT-5. Then try and mix it with water. If they don't mix, then it's really looking like DOT-5. Then mix the fluid with some oil. If it mixes, then you're almost assured it's DOT-5.

Anyway, that's how I would do it....

Cashburn · #3 (**permalink**) 03-07-2014, 08:22 AM

Should be High Temp DOT 4. The DOT 5 would be purple and they stopped using it many years ago. If you replace the switch relatively quickly you won't lose a drop.

cbreez · #4 (**permalink**) 03-07-2014, 08:36 AM

Buy a couple of those switches as you WILL be replacing them every year or two...heat from headers kill them...

joyridin' · #5 (**permalink**) 03-11-2014, 06:12 PM

DOT5 is silicon based. Silicon repels water whereas regular brake fluid will absorb it. It should not be mixed because the DOT5 could repel areas of high moisture and cause pockets of moisture. You could lose your pedal if these high moisture areas get hot and turn to steam or become displaced during heavy braking.

I bought moisture strips some years ago from Autozone to test the moisture content. There will be no moisture content in DOT5 fluid.