FMTV Leaking Air when brake pedal is pushed

[agazza2]

My truck has started to leak a lot of air when the brakes are pushed. It was coming from the rear of vehicle, so was hard to diagnose just by myself. I used a rod to hold the brakes while I diagnosed where the leak was coming from. The leak was coming out of the exhaust valve on the Tractor Protection Valve which is located directly on the cross member above the rear axle. This is a common problem, but finding a completely new part is a problem as it differs slightly from commercial truck applications.

The original complete Tractor Protection Valve is Midland/Haldex RN50012. Everywhere I checked it was not available due to being marked as Military only.

The rebuild kit part number is Midland/Haldex RN31BC. NAPA lists it online, but my NAPA could not get it, but I found it on FinditParts.com This kit is the most complete one I found, and is only missing one round disc, as the military had one extra section on their tractor protection valve. Order 2 kits for a complete set to rebuild. Here are a few photos of the valve. If you search Haldex KN34101, KN34111, KN34130 ect there are many parts that very close. I think KN34101 would be a direct replacement based on my research but may require one or two adapters for the lines.

 

[FloridaAKM]

I went thru the same thing you did to stop the air loss, except that the fine fellows here directed me to the repair parts suppliers & what to look for. Search the threads for the last year or so for any other problems you come up with. Another thing that will give you problems is the diaphragms in the shuttle valves on the left front side of the truck, under the cab. You can replace or repair them @ your discretion. Good luck with your truck!

 

[scottmandu]

I was able to find an off the shelf aftermarket valve. I don't recall the part number though.

 

[Rene M]

Today i installed the new KN34101 and it vents worse... not sure yet why but i would not recommend that valve just yet.

 

[agazza2]

Today i installed the new KN34101 and it vents worse... not sure yet why but i would not recommend that valve just yet.

That is strange as when you reference the Haldex site and enter the Part number for the Military Part N50012 it cross references the OE Part number N30162RD which is the same as the KN34101. Is the same exhaust valve installed? Where all the connections the correct thread on this model?

 

[Rene M]

Today i installed the new KN34101 and it vents worse... not sure yet why but i would not recommend that valve just yet.

Well, i would like to take this time to say.. it works better when you put the 3/8 plug back in the top of the valve. oops.
=you do have to put two adapters in one side because the ports are 1/2 not 3/8.
other than that .. works great.

 

[agazza2]

FMTV Tractor protection valve repair kit

Here is a photo of the Haldex repair kit RN31BC

 

[agazza2]

Well, i would like to take this time to say.. it works better when you put the 3/8 plug back in the top of the valve. oops.
=you do have to put two adapters in one side because the ports are 1/2 not 3/8.
other than that .. works great.

Thanks Rene for the follow-up. Now we have a replacement part and a repair kit for this item on the FMTV that is prone to failure.