Park valve venting out exhaust

[dhirocz]

Rebuilt my mv3 valve this weekend, since I haven't given it any love since I had the truck and recently I started noticing it leaking out the exhaust port with the truck in park with the foot pedal allied only.

Valve works fine. Except it still leaks. Doesn't leak with the tractor brakes released.

From what I can find, some troubleshooting matrixes mention that either the two way valve or the quick release valve can backfeed into the park valve and cause this issue. Some also mention a bad foot brake valve.

I'm still waiting for my service manual to arrive. Until then I don't have any air system diagrams specifically for this truck to help pinpoint the source of the problem, so any advice would be helpful. I'd rather not throw parts at it, even though at their age I might replace them all as a function of preventative maintenance.

The park valve works fine otherwise.

[imalumberjack]

My two cents? replace them .... I have never had any long term fix by rebuilding it was only a short term patch.

[pearce trucking]

I've got my transmission and drive shafts out rebuilding my cm871. I know I'm going to replace the three separate valve bodies under there along with most hoses while its all easy to access. 700000 miles.

[dhirocz]

Ok so I'm very dissapointed in Bendix right now... new tractor protection valve was jammed open. 2 weeks old.

I rebuilt my old one, and though it was working fine, I replaced it with a new genuine Bendix TP5 because it had a rough life. The new valve lasted two weeks. Why? The tractor protection circuit had a plastic valve...not metal like the OEM...that was dimensionally inaccurate and jammed 1/2 open in the bore.

I removed my metal valve from the one I rebuilt and installed it. Voila! No more problem, moves freely as designed.

I guess Bendix is moving towards using cheaper China junk. Knowing this, I will make sure to keep my old valves around in case I get another dud.