M656 "tractor-trailer protection valve" is venting my air

[sangamon]

I was going to take the M656 for a spin yesterday, but couldn't get my air pressure above about 50 psi.

I discovered that the tractor-trailer protection valve was releasing a lot of air through its vent.

The valve is FSN 2530-907-0668 or part 8738146

I removed the valve and am ready to take it apart.

Is there anything special that I need to be aware of, like strong springs?

Thanks.

 

[NDT]

I believe that is a standard 18 wheeler part obtainable from a truck parts house.

 

[emmado22]

I'd buy a new one. Should be a standard part from a big rig shop. You night not get the exact phyiscal replacement, but you'll get one thats functionally the same. Brakes arent the place to be looking to save a few bucks.

 

[cranetruck]

Here are a couple of drawings that may help.
There are some differences in the hook-up on my 757, but the image shows yours.

 

[sangamon]

I keep forgetting that most of the parts on the M656 are standard, ordinary, "farmer" parts. I'm used to buying Unimog parts which are only made by elves in the Black Forest of Germany!

It's a standard Bendix TP-2 valve, and is no longer available. I can't complain too much - they were made for over 30 years.

The TP-2 has been replaced by the TP-3. The TP-3 is not a drop-in replacement, as some re-plumbing needs to be done.

My TP-2 is mostly just dirty, except that the spring on the bottom is partially rusted. I need to ponder on finding a new spring, or re-plumbing for a TP-3. I'll also look around for a "new" TP-2.

I suppose I could un-plumb the trailer protection system completely, since I don't have any plans to pull a trailer. However, I'm trying to keep the truck as stock as possible.