HMMWV Brake Fluid DOT 5 HELP!!

[scottofazphx]

So I picked up a M1152 that was purchased from GovPlanet couple years back and has been sitting ever since. When I got it delivered to me, I noticed when brake pedal was engaged fluid would squirt out at the proportion valve. Well come to find out someone took off the one hose that cost like 300 bucks. Anyways I ordered up the hose and a fresh 1 gallon of DOT 5 brake fluid (purple), installed the hose and was about to refill the reservoir so I could bleed the system and noticed the fluid did not look purple. Upon further inspection the fluid is clearly yellow, see attached photo.

Question for the community is, Is the military still using DOT 5 in the maintenance of these trucks or did they switch over to DOT 5.1 (yellow) over the years? The cap on the on the reservoir make this even more confusing since it appears to say to use only MIL B 46178 Fluid. I cant find any data on this fluid at all.

Im basically at a loss, do I flush the entire system and install fresh DOT 5, do I use DOT 5.1/3 and hope for the best or is there really a 46178 fluid out there. Maybe i need to drain some fluid at the rear of the truck and see if its yellow or purple to see if someone topped off the system with DOT 3.

Thanks for any advice you guys might have!

 

[MarkM]

DOT 5.1 is NOT a silicone brake fluid. Dot 5 is.

DOT 3,4 and 5.1 are all glycol-based fluids with the major differences is the boiling point.

 

[Coug]

A complete system flush is always a good idea if there is anything unknown about what fluid is in the system.
At that point you can run whichever fluid you want to, though if it were mine I'd try checking at the brake calipers what fluid color comes out first.

 

[Coug]

B-46176 (not 8 ) is mil spec silicone brake fluid.
It's difficult to tell the 6 and 8 apart on stamped covers like that.

 

[scottofazphx]

A complete system flush is always a good idea if there is anything unknown about what fluid is in the system.
At that point you can run whichever fluid you want to, though if it were mine I'd try checking at the brake calipers what fluid color comes out first.

Yea im thinking it's probably best to remove some of the fluid left in the reservoir and test it to see if it mixed with water. Maybe they used a yellow DOT 5, seems it exists. Then I think I'll bleed some out at the rear caliber and do the same and/or see if its purple. If still unclear I agree prob best just to flush entire system. I have a new 1 gallon of mil DOT 5 so that i assume is enough.

 

[GopherHill]

I think DOT5 yellows as it ages. Do the water test on the old fluid.

 

[scottofazphx]

I think DOT5 yellows as it ages. Do the water test on the old fluid.

Yep, that's what I found out. I tested the old fluid and its DOT 5. separates water just as it should. Thats a relief, now just going to bleed lines till I get new purple fluid coming out and call it good. Thanks for all the info and hopefully this short thread will help others in the future.

 

[Retiredwarhorses]

Yep, that's what I found out. I tested the old fluid and its DOT 5. separates water just as it should. Thats a relief, now just going to bleed lines till I get new purple fluid coming out and call it good. Thanks for all the info and hopefully this short thread will help others in the future.

DOT5 doesn’t remain purple….just verify whats in it and bleed the brakes out as normal.

 

[MarkM]

The problem with DOT 5 is it does not absorb water so if it's old and the system has collected water it naturally flows to the lowest point in the system and rots out the lines in that spot.

 

[mgFray]

Can confirm, my HMMWV had yellow fluid in it that was tested as DOT 5. Stuff I added when I bleed the system out was purple as well. Turned more 'maroon' in color one blead through the system. My take, only the color in a new un-opened bottle can be trusted.

 

[Vapor Trail]

Which type was in a 2004 M1123? Not ABS and newer than 98 so I'm in a gray area. The brake system was missing so I don't have anything to check.

 

[Coug]

Which type was in a 2004 M1123? Not ABS and newer than 98 so I'm in a gray area. The brake system was missing so I don't have anything to check.

Every truck should be DOT 5 if it wasn't equipped with ABS.