Brake Fluid Problems - Mixed DOT 5 and 3?

[Speedzilla]

Hey Guys,

I am trying to help a friend with a HMMWV with some braking problems. Popped the master cylinder cap and found two fluids that were NOT getting along well, you could see two separate materials clearly, and some of it seems to have coagulated slightly. Does this look like a mix-up of DOT3 and DOT5 to you guys? I assume its not really likely, or possible for the fluid from the booster to enter the MC? I assume several seals would have to go out, but I am not sure. The brake warning light is on, and it feels like the brake pedal is soft, and doesn't feel like there is a lot of assist. Thanks for any input!

 

[juanprado]

could be a mixture. You can use a turkey baster / fluid bulb and r&r fluid in master cyl and flush/bleed but you have classic symptoms of a bypassing internally master cyl failure. I would change master cyl and flush whatever fluid out you can.

 

[Retiredwarhorses]

Just start by flushing it...the dot 3 won't ruin anything. Plenty of people have switched over to dot 3 from dot5.
you just don't want to mix the 2. Choose one or the other, just not both. People have also changed the PS fluid over from ATF to steering fluid as well, it just has to be flushed out for the change over.

 

[racing4funn]

could be and more likely water.

 

[dependable]

Dot 5 is usually light purple when new, and turns clear over time. That red stuff floating on top looks like it could be ATF. Is it oily? If so, you may have to do more than flush the system.

When I mixed dot 3 & 5 (a long time ago, so I could get home with brakes) it cause the calipers to seize up onto rotors, but it did not happen right away.

 

[Karl kostman]

Just to be sure that you have not mixed the two (DOT 3 and DOT 5) I would flush the entire system as good as you can with either 3 or 5 then fill the MS with whatever you choose to run. Mixing a water silicone based fluid with a NOT silicone base brake fluid will in the end cause you a whole lot of misery!!!
KK

 

[dmetalmiki]

I drain ALL my vehicles of dot5. and replace with cheaper and easy to obtain and replace dot 4.

 

[FloridaAKM]

I run Dot 5 in my trucks because they came that way & it was too much work to flush & refill!

 

[Bill W]

According to Army TB below ( read para,3,A ) you can mix dot 3 with dot 5 in the meantime while awaiting full conversion to BFS
http://ccsurplus.com/sites/ccsurplu...-0002-87replacement procedure brake fluid.pdf

 

[Action]

According to Army TB below ( read para,3,A ) you can mix dot 3 with dot 5 in the meantime while awaiting full conversion to BFS
http://ccsurplus.com/sites/ccsurplu...-0002-87replacement procedure brake fluid.pdf

Could any of that info have changed since it was published 34 years ago?

 

[Bill W]

Action
Anything is possible.
Have you got something more up to date that supercedes this info??

 

[Action]

i havent looked for anything. I just use DOT 5. I think I read that DOT 5 will not eat paint like DOT 3 will. not that that matters with CARC?