M151A1 brake fluid

[billystuart]

What type of brake fluid is used in the M1561A1?

 

[m816]

Silicone

 

[glcaines]

what type of brake fluid is used in the m1561a1?

dot 5

 

[poppop]

The Military used silicone, which is DOT 5 because water will not mix with it. A lot of these vehicles sat for long periods of time, so with water inspersed in the fluid componets would rust. I have rebuilt several systems that were extremly cruded up but the componets honed clean quickly with no pitting. When I rebuilt the brakes on my M151A1 I opted to use DOT 3 because of the price difference. I drive it regularly and have had no problems with the brakes in the 8 years since I put DOT 3 in it. I have one duece I use on the farm and have DOT 3 in it with no problems. The two types will not mix so you need to be sure what was in it before you add either one. DOT 5 is usually purple but can fade or lose its color all together. If you can get a sample out add some water and see if it will mix into the fluid. If it does then its DOT 3, if not its Dot 5. If it is five and you want to use DOT 3 then you must thourghly flush the system before adding. The same with the change the other way. We have some members who say they have mixed the two with no problems but flushing is the proper way to change. Why take a chance with something as important as your braking system.

 

[one2boost]

Yup, when I had a fleet of those, we strictly used DOT 5.

 

[nattieleather]

@billystuart I agree with Poppop. You need to determin which brakefluid you have. M15a1's are old enough that it is possible that they left the military with DOT 3 brake fluid in them as the Army didn't switch to DOT 5 until the early 80s. It is also possible that who ever owned it before you has been putting DOT 3 in because they don't know better or they figured out that was what was in it.