DJG

Ok Thanks, I will try that

sounds like the shoes are stuck on the drum try to loosen the wheel cylinder then use a good puller on it with some heat and PB blaster oil on it I think that's how I removed my uncle's but it was  a long time ago I might have even put a rolling jack under the free wheel and dragged it back and forth with another fork tuck to loosen it up.

they are new just old truck dropping sand all over every thing no air leaks all relay valves changed out and checked out the only air is coming out the vent on the left rear relay valve when brakes are released. checked hoses ok could it be a bad brake chamber leaking from one side to the other ?

Thanks, But he put two brand new valves on and it still leaks when the brakes are released.

Does it have an water type oil cooler if so check to see if that is plugged I had one once on cat motor that drove me nuts once I boiled it out it ran nice an cool

Need some help a friend gave me a 1985 Mack dump truck to fix after he changed out a lot air valves the problem started with a bad brake chamber he replaced it with a new one and he told then air started leaking from the back left side relay so he changed them all but air still coming out of it when brakes are released. could the new air chamber be bad ? 

Need some help a friend gave me a 1985 Mack dump truck to fix after he changed out a lot air valves the problem started with a bad brake chamber he replaced it with a new one and he told then air started leaking from the back left side relay valve when brakes are released so I took all the valves apart they all ok air is getting to all of them. it is a  MODEL DM685S

Thanks Dan

Vin #1M2B120C1FA055812