brake problem with m35

[2deuce]

The air pack was frozen and the brake pedal was rock hard. I obtained a used air pack and installed it, built a power bleeder and bled the brakes. After bleeding I had about a half pedal without air. I started the truck and built up pressure. Still had the same pedal at first. I turned off the truck to listen for the air pack working but couldn't hear anything. Then started hearing a gurgling noise in the MC and then the pedal went to the floor. Sometimes I could feel some resistance in the pedal but it would release and then go to the floor. When I let up on the pedal a lot of fluid and air would come up through the MC that could be seen because I had the cap off. There is no air in the MC unless I push the pedal to the floor and then release it. The fluid level remains constant in the MC. Do you think the air pack failed? or could it be the MC?

Thanks

 

[welldigger]

Pull the rubber boot off the MC. If there is brake fluid in the boot then your MC needs rebuilt/replaced. However the symptoms you describe mirror what my truck was doing. My air pack was totally shot so I had to buy a new one. My MC was also bad but I had a firm pedal even with the MC seeping fluid. It sounds like your used air pack needs a rebuild or replaced. Air seems to be bypassing the inner seals of the air pac piston shaft and getting into your brake fluid.

 

[2deuce]

I haven't had an air pack apart, so I don't have an understanding how it works, but it sounds like I'm going to get some experience. Quite a lot of brake fluid is coming up with the air when I let up on the pedal and it doesn't come up instantly, it boils up after a second or two after the pedal is up. Thanks

 

[welldigger]

Yup your air pack is toast. Don't do what I did and buy a rebuild kit before you at least pull the large end off. The large side is the air side. It has a tendency to collect water and rust up. If the pitting is too deep to hone out its time for a whole new one, don't bother trying to rebuild.