Installing the Pressure Relief Valve on the M35A3

[glcaines]

I finally got around to installing the 4820-01-490-1773 pressure safety relief valve on my M35A3 compressor. The installation is covered by MWO 9-2320-386-20-2. All M35A3s were required to have this kit installed prior to 30AUG05, but for some reason my truck did not have the kit installed. Catastrophic failure of the air pressure system can occur if the air pump continues to build pressure uncontrollably. I'm not sure what the weak link is that lets go under these conditions. It only took about 20 minutes to install the kit. According to MWO 9-2320-386-20-2, you are supposed to replace the compression nut and attached ferrule. I did not do this because to do this required cutting the copper tubing to shorten it and there is not enough room to use a tubing cutter without removing the section of copper tubing to grant more room. The existing nut and ferrule were in excellent condition and after assembly, there were no leaks. I did have a little trouble screwing the 'T' into the top of the compressor because the hose next to it was in the way. I was able to pull on the hose and gain just enough clearance to screw it in. According to photos in the MWO, the hose is mounted slightly to the side to gain more clearance. My truck was not like in the photo.

 

[ryan77]

Pics???

 

[steelandcanvas]

Gary, Who stocks that kit?

 

[glcaines]

Gary, Who stocks that kit?

I found mine on E-bay. They appear to be present on E-bay almost continuously from several sellers. I think I paid $7.00 for mine, plus postage. A good price if the alternative is a potential explosion. I added some photos.

 

[steelandcanvas]

I found mine on E-bay. They appear to be present on E-bay almost continuously from several sellers. I think I paid $7.00 for mine, plus postage. A good price if the alternative is a potential explosion. I added some photos.

Would it be a good personal MWO for an A2?

 

[glcaines]

I'm not sure if the A2 already has a pressure relief valve or not. The TMs should say. If not, the one designed for the A3 should work, but you would need to change fittings.

 

[Rustygears]

Not only is it a good idea from a safety point of view, but it is required equipment on any street licensed vehicle with air or air assisted brakes and must limit system air pressure to under 175 psi. It is a federal DOT requirement that each state codifies in its motor vehicle regs.

 

[Floridianson]

Would it be a good personal MWO for an A2?

The A2 has a saftey valve on the top of the air tank.

Would like to have seen a better pic of the valve before you installed. Looks more like a oneway valve the a blow off.

 

[glcaines]

The A2 has a saftey valve on the top of the air tank.

Would like to have seen a better pic of the valve before you installed. Looks more like a oneway valve the a blow off.

The valve itself is as follows:
Valve, Relief
P/N N-1178-DF
CAGE: 06721

Attached is a photo of the valve by itself.

 

[AnonymousOne]

I thought I would post my pictures on how I installed my "Pressure Relief Valve" on my M35a3 / 1993

As stated by the original poster above this is required to prevent failure.

Reference numbers for searching
NSN 4820-01-490-1773
MWO 9-2320-386-20-1

Note - plugging the old copper pipe into the new fittings required some interesting foot work. As the new fitting is about an inch longer than the original part, the fixed length copper pipe needed someone to lightly stand on the copper pipe bend with soft soled sneakers until the copper pipe lined up with the new fitting so it could be screwed in The kit does come with a replacement copper pipe connection so you could cut off the old compression fitting and use the new one with the new connector but I didn't want to risk having the pipe be too short .. that would be a disaster.

 

[rtk]

pressure relief valve

I let my fingers do the walking , but could not find a kit on line , Just wondering if you could just use a air brake relief valve from a NAPA truck parts outlet , should be just as good . The rest of the kit is just brass fittings that you can get at NAPA as well . Bob k

 

[glcaines]

You can find them on E-bay for less than $10.00. Search for MWO Kit.