m51a2 Brakes will not release after driving a distance
I have a 5 ton dump truck where all the brake componets have been replaced. Master cylinder, hydravac, wheel cylinders etc. Brake master has more than required 1/2 inch slack. two new hydravacs have been installed. Around the field the brakes work perfectly. stops on a dime and releases pressure properly. Put the vehicle on the road and travel variable distance of 7 to 20 miles at speeds of 45 mph or greater and the truck stops fine but retains air pressure on the brake light switch and the booster... thus the brakes are locked. Bleed master cylinder at bleed nipple without any release. Pressure must be released from outlet on booster to release. Anyone have a clue as to the problem? Compressor, pressure regulator and all else check out fine. Thanks for any clues
Location: Northern Michigan - Tip Of The Mitt - Squaw Creek
Posts: 1,462
first off be sure to add your location to your sig line. on the brake issue, my XM818 had the same issue when i bought it.matter of fact the prev owners made sure they showed me where they left the wrench to bleed of a little fluid when it locked up. turned out to be the glad hand cover on the right front had the little vent hole plugged and was retaining pressure. i know it does,nt make a lot of sense but after cleaning the vent it works just fine for 3 years now.I admit that it drove me nuts for a couple days until i figured it out.
RE: m51a2 Brakes will not release after driving a distance
check the vent on the glad hand cover on right front fender. if plugged, your brakes will lock when applied. Had same problem on my M51A2, replaced everything with new parts, had to bleed every time I used the brakes. Pulled some hair out, listened to Wrecker One from NJ and fixed my problem. JT
The older I get, the more I know I don't know, but how I love a Deuce
RE: m51a2 Brakes will not release after driving a distance
That special glad hand cover for the right front comes in two versions...one has a differential type vent on it and the later one has a little hole in the center... both performing the same function... letting out air which creeps by the check valve for remote application of brakes when towing. That line needs to breathe.
RE: m51a2 Brakes will not release after driving a distance
Thanks a bundle for the responses. Truck was missing glad hands on the front when I bought truck and replace them with general commercial units. Will try the suggestions and find vented unit. MANY Thanks
This is somewhat the same problem we have with the water truck, but the brakes do not lock or bind. Tried venting the right front line (no glad hands) but the brake lights still stay on, and no air comes out. Takes between 1 and 5 minutes to go out, depending on how hard the brakes are used. MC, brakes and hydroboost all in good shape.
mbware, you don't need to buy a special part, just drill a small hole in center of the one you have on it. Start with a 1/16" hole. You'll be all set. JT
The older I get, the more I know I don't know, but how I love a Deuce
m51a2 Brakes will not release after driving a distance
