LMTV Air Brake Issue...

[Augdog1964]

Hey all,

Did a precursory look at the TM, and couldn't find this particular issue...

When I press the brake (for instance at a stoplight), the rear brake set does not just dump air and lock, it continues to dump air.
At a long light I start to lose system pressure as the system continues to bleed.

Its so loud back there as it bleeds, its almost impossible to find where its dumping... almost sounds like its inside the bed crossmember...

Anybody else have this? Any ideas how to fix and track down?

Thanks!
Dave Bane

 

[porkysplace]

With the truck shut off pressurize the system with your shop air compressor, you will be able to hear it then.

 

[Suprman]

Could be the tractor valve needs to be rebuilt. Common issue.

 

[Andyrv6av8r]

Could be the tractor valve needs to be rebuilt. Common issue.

This. Diaphragm needs replaced.

 

[FloridaAKM]

Get a tractor valve rebuild kit, pull the valve off the frame over the rear axle, rebuild, replace & you are back in business without the air leakage. It is easy with common tools & a little time. been there, done that, but got no t-shirt.

 

[snowtrac nome]

sounds like your qr valve on the frame I usually replace them on commercial rig they have so much corrosion its a waste to try to rebuild them.

 

[Augdog1964]

Ok thanks guys! Tractor valve it is... anybody have a source for a new one, or the rebuild kit?

 

[Andyrv6av8r]

I may have a spare kit.

 

[Augdog1964]

Got the rebuild kit ordered... thanks guys... found the numbers in the link to a previous thread... looks easy.

I would be interested in any part number on the TPV Valve itself... but I'll see if I can find it on the part during rebuild.

Andy, thanks! I got one coming!

 

[FloridaAKM]

Finditparts, Haldex P#RN31BC for the tractor valve repair parts, not to pricy! For shuttle valves, Haldex P# KN25060 for the new units. Info for those who need new parts in the future.

 

[Oxyacetylene]

It may also be a faulty service brake diaphragm. Crank the truck and let it build up air pressure, then shut the truck off. Chock the wheels. Have someone else press and hold the brake pedal while you are under the rear of the truck so you can find the exact place the air is bleeding from. The tractor protection valve is on the crossmember and when the one diaphragm goes bad it will vent air from the top of the valve. If the air is coming from the vent line mounted to the frame rail, then you probably have a bad service brake diaphragm. Mine had a hole in it, and when holding the brake the air pressure would vent back through that line.

 

[Oxyacetylene]

Were you able to isolate the air leak?

 

[expeditionnw]

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