I have a 1985 F-700 with the 429 in it. It is a dump truck that I use quite frequently. However, I've started to have some brake problems. When the truck is running, it sounds like brake fluid is gushing thru the lines. Whenever I depress the brake pedal, it makes a big flushing noise and the brake pump on the engine whines horribly. The truck is equipped with a hydraulic parking brake system which works fine. Ive still been driving it with those noises and it seems to stop ok, but im worried that one day I will totally lose my brakes. Does anybody have any idea what is going on?

 

check the fluid first off. The hydraulic parking brake also provides you with pressure for your power brakes.

That truck will NOT stop without the brake booster working.. Trust me.

You dont want to work the truck with low fluid. Mostly because if its low, its leaking somewhere..

 

Ive checked the fluid level and it is fine. The parking brake holds the truck very nicely. I guess maybe the pump is going bad but so far I havent been able to find a replacement.

 

There's a filter inside the reservoir. Maybe its plugged up. Its normal for the pump to make some noise under a heavy stop situation. Hard to say whats going on without seeing it and hearing in person. Does the pedal feel firm when its making noise, or does it pop or shudder with the noises?

Maybe nothing.. These things get old and make funny noises. Its up to us as the owner operators to decide which noises constitute repair.

It must be something to do with the pump since the brakes are working otherwise and the noise is coming from the pump area..

A hydraulic shop would put a tee on the pressure side and take some readings both without a load, and under a load. Im not sure what the system is made to run at, or what to really test against. You may be able to call Ford to find some test procedures..

Its possible that the relief is gummed up and causing the pump to over pressurize the system, then it pops in and out of bypass, making the growling noises..

 

I didn't know there was a filter on the inside. I guess i'll have to check that out. Also, another thing I didnt mention before was after I drive the truck somewhere, a little brake fluid comes out what seems to be a relief hose coming out the top of the reservoir. That may be caused by over pressurizing the system. Any ideas?

By the way thanks rummur s c for all the help so far!

 

Sounds like there is air in the system..