LMTV brake valve leaking when pedal is depressed?

[scottmandu]

I tried to get the truck inspected and they wouldn't pass it due to an air leak when the brake pedal is depressed. I've tracked it down to one of the valves (the right one if sitting in the drivers seat) that has 3 air hoses going to it above the rear axle. Odd thing is that both of my LMTV's has this air discharge when the brake pedal is depressed. It looks like it might release air under normal operation but I'm not terribly sure.

The part looks to have some sort of vent cap on it. It is a Haldex brake protection air valve.

NSN: 2530-01-360-4446
Part Number: N-50012

 

[NDT]

If you ever had to drive down a mountain grade in an air brake truck, it would be clear to you why you would not want your air to be pizzing away when you apply the brakes. Follow the diagnostic tree in the TM and replace the defective part(s), which it sounds like you have already identified.

 

[Ue413]

Mine does the same thing.....and although I took that valve apart, still haven't found the source. Regardless, can you identify the source for your valve once you replace?

 

[Andyrv6av8r]

Sounds like your tractor protection valve diaphragm is bad. An easy repair.

http://www.steelsoldiers.com/showthread.php?144109-Air-Brake-Protection-Valve-leaking-venting

 

[Retiredwarhorses]

Been there done that...napa has a rebuild kit for 27.00
mine did the same thing...total time to remove, rebuild and install is about an hour.
the diaphragms go bad...mine fell to pieces when I opened it up.
need to get the part number when I get to the shop...

 

[Retiredwarhorses]

Part number RN31BC Napa...they ordered it from Haldex.

 

[scottmandu]

Yup figured it out. It was the tractor protection valve, cost me all of about $140 installed to fix. I kept my valve and took it apart and it was filled with sand.. Oh joy I wonder what else could have sand in it!?

 

[Retiredwarhorses]

Yup figured it out. It was the tractor protection valve, cost me all of ab out $140 installed to fix. I kept my valve and took it apart and it was filled with sand.. Oh joy I wonder what else could have sand in it!?

Figured it out? we told you what part to replace...LOL
its amazing how simple some fixes can be..that's an easy one...the part replacement that is...

 

[scottmandu]

Figured it out? we told you what part to replace...LOL
its amazing how simple some fixes can be..that's an easy one...the part replacement that is...

Yup figured it out about 10 minutes after I made the original post. I just found it odd that both trucks did the same thing so I guess it's a common failure or I'm just that lucky (not).

 

[kenet3621]

Once Andyrv6v8r pointed me in the right direction, I found the Haldex RN31BC here...

https://www.finditparts.com/products/370234/haldex-rn31bc

 

[kenet3621]

Here is the old diaphragm that was in the TPV (Tractor Protection Valve). Easy to see it was totally wasted...



New one installed in less than 10 minutes. Press the brake pedal and no pressure lose in front or rear air systems! Back on the road.

Thanks to Andyrv6av8r!