What is this part? (Air System under dash)

[TMNT]

Ok guys, the service air valve under the passenger dash is leaking around the "on/off" handle. It makes foam and bubbles pretty bad when sprayed with soapy water.



I want to replace it but I can't find it on any parts list and it doesn't seem to be on any of the air system diagrams in the TM's. I've searched several of the usual suppliers, (Erik's, TNJM, Saturn, Memphis) but i don't see one there. Does anyone know the proper name or part number for this valve? Does anybody have one that doesn't leak?

 

[gimpyrobb]

Can't you tighten it up?

 

[TMNT]

Can't you tighten it up?

It's not leaking from the connections. It's actually leaking out where the valve handle comes out of the valve body. I don't see a way to tighten that, but I haven't pulled it out of there and worked on it just yet. It's just a valve that feeds a T for hose couplings. I guess I could replace with Home Depot air line parts, but I like keeping the truck true to its original design.

I've been tracking down and fixing the leaks in the air system. The pressure regulator (governor) was leaking like crazy and so were several fittings around the regulator. I fixed all of those. My other leaks are this under dash valve, the air gauge hose, and the air-shift hose. All of those are making foam at places other than the fittings.

 

[gimpyrobb]

Ahh, pull it out and put new O-rings in it. Should be good to go.

 

[gringeltaube]

Not sure about the O-rings, Gimpy. Those are so-called plug valves... (quarter-turn, 3-way, tapered-plug, spring-loaded... in this case) They are all metal to metal contact; at least the ones I have seen so far. And that one pictured looks very similar, although we can't see the spring.

In most cases if a plug valve starts leaking it can be fixed via a little sanding/grinding, and re-assembling with heavy (synth.)grease. I have yet to find one that was worn out beyond possible repair.

See this related thread...


G.

 

[TMNT]

I think I'll try taking it out and refurbishing it. It didn't realize that the valve might be repairable.

 

[gringeltaube]

LOL... what is NOT repairable on these lovely trucks? ... a blown tire, maybe.....??

G.

 

[welldigger]

LOL... what is NOT repairable on these lovely trucks? ... a blown tire, maybe.....??

G.

That strongly depends on who you ask.

 

[KsM715]

It's just a valve that feeds a T for hose couplings. I guess I could replace with Home Depot air line parts, but I like keeping the truck true to its original design.

The "T" and air line fittings are not original to the truck so why not just get a new and reliable valve to put in its place and keep the old one as a project to work on for a rainy day.

 

[brianp454]

For the time being you can plug it you need to drive the truck.

I went out and looked at my truck. I think the booger in finding a replacement would be the two screw mounts. An option would be to get one surplus or from a local guy that parted one out. I imagine that you talk to some other local folks with military vehicles and can maybe help out.

Also, it looks like mine has an e-ring or something that is spring-loaded. It looks like removing it will allow for disassembly, cleaning, etc. If it does have o-rings or other seals you might want to include a bit of silicone oil\grease, petroleum jelly, etc. to lube them for easier operation. I also find that they do not tear as easily with a bit of lube.

Best!

 

[TMNT]

The leak is small enough that it doesn't prevent driving the truck. I have been driving it that way for a year and a half. I didn't even know it was leaking until I started looking for leaks last weekend. I was hoping to get the system to hold air for more than a few hours without leaking down to zero.

I would buy a new valve if I could find one. Otherwise, when i have some time, I'll take this one out and refurb it.

I think that the two under-dash hoses are the bigger leaks. Both were blowing bubbles and making foam in several places. I found replacements for them but I'm thinking I'll replace the hoses with new DOT airline and push on fittings.

After those repairs are made, my system should be pretty tight.

 

[TMNT]

I removed the plug valve from the truck, disassembled it and cleaned it up. There was a fair amount of green and white corrosion. I polished up all of the mating surfaces, lubed it with Teflon grease, and reinstalled it.

I also finished replacing the air hose to the gauge and the one to the front axle switch on the dash. I replaced those with DOT brake line and push-on DOT connectors.

The plug valve still leaks air, probably more than before. All of the other leaks are gone. I took out the plug valve again and replaced it temporarily with a ball valve from Lowes.

The part number for the valve is MS500046-1 and NSN 4820-00-753-3853. It appears to be used on several vehicles and even in some aircraft applications.

 

[rmgill]

Try lapping the plug with a bit of tooth paste or fine polishing compound...

 

[cranetruck]

.....
The plug valve still leaks air, probably more than before. All of the other leaks are gone. I took out the plug valve again and replaced it temporarily with a ball valve from Lowes...

If you are going to use the valve in its intended application, keep in mind that it must vent when turned "off" (the air pressure to the front drive engagement mechanism must be released)...

 

[Heavysteven]

I use soft set #5 pipe dope on my connections.