LMTV air system dumping at purge valve

[Konichiwa512]

In the rain last week while helping a friend retrieve his P-24 fire truck from GovPlanet, my M1078 started releasing air pressure from the purge valve below the air dryer every 10 to 20 seconds. It has since dried out, but the air keeps dumping. Air gauges are holding steady at 120psi and the truck operates normally other than the constant release of air from the purge valve. The troubleshooting steps in the MX manual only say, "Notify DS Maintenance," and I have not found a thread on this problem for the LMTV.

 

[doghead]

Service the air dryer.

Clean the purge valve.

 

[simp5782]

Which dryer do you have? The circle type with fins or have you updated to the Haldex Purest Dryer? You should be able to stick a screw driver in the purge valve hole and force it back closed. This is a common problem on the M939 trucks.

It is a stuck purge valve but by knowing which type I can get you the correct part number for a new O ring and lower half rebuild for that particular dryer.

Suprman sells an updated Purest type air dryer or he did have some in stock. Or you can get an Wabco Air Saver Dryer from member FuzzyToaster.

 

[Konichiwa512]

The LMTV is '92 model with a cylindrical dryer with cooling fins.

 

[simp5782]

The LMTV is '92 model with a cylindrical dryer with cooling fins.

Major dryer service kit haldex #DQ6030 or # 419784

Graver pure air dryer. Kits are found on eBay fairly cheap. Rebuild/service the dryer with this kit or contact one of the members above for a newer air dryer style

Sent from my SM-G935P using Tapatalk

 

[FloridaAKM]

Get the newer style Haldex dryer from vendors here. I played the repair the cylindrical dryer game (full of goo) long enough to find out I was wasting my time & bought one from Suprman. Here is a picture of the install. No more problems now.

 

[Konichiwa512]

Does the new dryer replacement kit come with the mounting plate?

 

[simp5782]

No. It is available thru napa. DQ6051 or just drill your bolt holes yourself.


Fuzzytoaster has a dryer version as well that I am using that seems to work quite well and cheaper parts for it. Only difference is that you have to get a few fittings to make it work since they are boss fittings.

 

[wandering neurons]

As a former Tucson resident, it normally doesn't get super-cold there. So how cold was it when you had the problem? If near freezing, check the heater on the bottom of the drier. I had my purge valve freeze open due to Maryland cold weather and water venting from the valve. Electric connector between purge valve heater and the LMTV chassis wiring was damaged, heater didn't work, water froze in the valve, couldn't build air pressure, couldn't use the truck to pull my wife out of the ditch she slid into. Had to use my 4x4 kit truck (see signature for info) to free her.
Check voltage and ground on the plug, resistance of the heater. Start the truck, remove the small plastic shroud around the heater, and feel for warmth.
Worked for me, but I also just ordered a Suprman Special newer-model drier, should arrive Thursday.

 

[snowtrac nome]

Usually when this happens its a torn o ring in the purge valve, also look at the relief valve on top mine started leaking this winter and I had to replace it. its kind of balmy out right now around 7 degrees with a 30 mph wind.

 

[Konichiwa512]

I removed the purge valve and cleaned it, but the problem persists. It looks like performing the full service on the air dryer would be just as much work as replacing it, so I might as well do the upgrade and save future headaches.

 

[1951M1078]

I think you will be happy doing the upgrade. I am.

It will give you more time to repair all the other stuff you have not found yet ?