M35A3 Air Issues

[OGFDBrad]

I am a member of a local volunteer fire department and we have multiple military vehicles in our fire protection and rescue fleet due to there cheap and effectiveness qualities. I am currently experiencing and air issue on our all-terrain brush truck ie M35A3. The history of the issue started when the pressure popoff valve on top of the primary tank suddenly opened about a month ago and wouldn't close. I replaced the pop off valve with a new one rated at 120 psi. The old one coming off did not look corroded it just looked word out. All was well until about 2 weeks ago now I have no air pressure indicated and the pop off will pop off and close and will contiue to due so about every 2 to 3 minutes. When this is going on I can crack my tank drains and the pressure is no where near that of the pop off. Although there is always moisture in the tanks. The gauge never reads any pressure but the warning buzzer never goes off. I am fresh out of ideas and being a volunteer department funds are limited. Any help would be greatly appreciated.

 

[gimpyrobb]

Have you checked the air governor and/or the air dryer?

 

[welldigger]

2 things you NEED to do. Rebuild your air dryer and replace the air priority valve on the tanks. It looks sorta like an air regular. I believe it is mounted to the topside of the outer tank. Eriks military surplus has them I believe. They also have the air dryer parts you will need.

 

[OGFDBrad]

I was thinking air dryer/governor. Is there a way you can test them or is replacement the only test. And as far as dryer is just easier to replace whole unit as being without this truck right now for a very long period of time is not an option. And also what kind of cost could I be looking at.

Thanks Brad

 

[welldigger]

Definitely rebuild the air dryer. I think the kit is about $150 or it might even be less. Shouldn't take you more than an hour to do. It's very strait forward. The air govener is about $25. I don't know if there is a bench test for them. I think the air priority valve is about $60.

 

[OGFDBrad]

Also do you have a part number for the priority valve I am having issues finding it in the manual

 

[welldigger]

Give me a few and ill see what I can come up with.

 

[welldigger]

http://www.eriksmilitarysurplus.com/prprva28pr.html

Its cheaper than I thought. Only $25.

 

[OGFDBrad]

Ok. So just an update. I removed the air dryer and bypassed it for diagnostic purposes and still no air. So I then proceeded to replace the air governor as it was highly corroded. Still no solve to the problem. So I cross-referenced the number for priority valve and what to my suprise Napa had one so got it and swapped it and now everything works as advertised. Ordered kit for dryer and will rebuild as soon as parts come in. Thanks for all the help it is greatly appreciated.

Brad

 

[gimpyrobb]

Glad to hear things are starting to work!

 

[ProPower]

Spend the extra $25 dollars on the purge valve on the bottom of the air dryer! The Haldex rebuild kit does not come with one and they always seam to break!

 

[welldigger]

What happened is your air dryer got saturated with water. That allowed water to enter the air tanks and begin corroding the inside of the tanks. Water, rust, and crud got hung up in the priority valve stopping it up.

If you have an a3 it is important to maintain the air dryer. It will prevent many headaches in the future.

Glad to hear everything is getting fixed!!

 

[welldigger]

Spend the extra $25 dollars on the purge valve on the bottom of the air dryer! The Haldex rebuild kit does not come with one and they always seam to break!

The last rebuild kit my buddy got had one. I think it depends on which kit you get.

 

[gimpyrobb]

Spend the extra $25 dollars on the purge valve on the bottom of the air dryer! The Haldex rebuild kit does not come with one and they always seam to break!

You can buy them separate from a kit. You can pull the valve to inspect by removing a "C-clip", then decide if its needed. When I rebuilt mine, I inspected the valve and didn't need to replace it. I literally JUST rebuilt mine. PM with questions if you need any help.

What happened is your air dryer got saturated with water. That allowed water to enter the air tanks and begin corroding the inside of the tanks. Water, rust, and crud got hung up in the priority valve stopping it up.

If you have an a3 it is important to maintain the air dryer. It will prevent many headaches in the future.

Glad to hear everything is getting fixed!!

We have a member here in the classifieds that is selling the minor kit. After you rebuild the air dryer, you might want to stock up on some of his kits. Haldex had said the service interval on the "pure air plus" was bi-annually, but now they say annually. Just a heads up.