5 ton Brake problems

[kstate90]

I have a 1970 AM General 800 series 5ton 6x6 that I have been having brake problems with. It was originally a dump truck that we converted to a fire truck under FEPP. I noticed that the pedal was getting soft so I checked the fluid and it was low. Added about 1/2 a quart and got the brakes working. Went to drive it today and noticed a puddle under the truck. On the side of the air valve next to the master cylinder there is a vent tube and it appears that the brake fluid is coming out of that. Do I need a new Air valve? I assume that a seal inside the air cylinder valve has gone bad and is spitting the fluid out. We have 2 other trucks like this and have not had this problem. The master cylinder has been replaced at some point as it is painted white. I have brakes but not very good. Brakes need to be good on this as it carries about 1200 gallons of water. Thanks.

 

[Westech]

You mean the brake booster? If it is leaking out of that you probably can get a rebuild kit but if you don't want to mess with that swap it out with a good used or new unit. Even thinking of driving that truck even unloaded is not the correct answer.

 

[kstate90]

Thanks for the reply. I will call Kansas Forestry Dept tommorrow and see if they have a new one on hand.