Air Brakes

[3up]

Hello everyone,
Just made a deal on a 1992 M934 A2 with 17' Expando box. Selling class A motorhome and going to build out this live and travel in it. This is a Boyhood dream for me and my girl loves the idea. Anyway it blows air off every 6 seconds driving is this normal? It has a pyrometer but it goes past 1200 degrees easy. Is all this normal? My first full air brake system. Thank you Les

 

[98G]

My best guess says your PPV failed and your compressor isn't shutting off. You're hitting 150psi and hitting the pressure relief valve.

The root cause is moisture in the system.

Confirm my diagnosis and replace the PPV as a start....

 

[98G]

Also, I haven't had a pyrometer on an 8.3, but that sounds higher than I'd want to see. Insusoect someone tampered with the fuel settings.

 

[3up]

Awesome i will get one asap. Im checking the air filter too im looking for the easy fix . Thank you for your help.

 

[simp5782]

Way too much fuel for your elevation.

1200 would be max temp if the probe is in the manifold. 1000 if it's in the down pipe


Adding an intercooler will let you max the pump out pretty much and you won't see anything near 1200 even at 55000lbs. @profo has done this

 

[3up]

Intercooler? like a universal one? Is there one everyone on here likes?

 

[Mullaney]

Hello everyone,
Just made a deal on a 1992 M934 A2 with 17' Expando box. Selling class A motorhome and going to build out this live and travel in it. This is a Boyhood dream for me and my girl loves the idea. Anyway it blows air off every 6 seconds driving is this normal? It has a pyrometer but it goes past 1200 degrees easy. Is all this normal? My first full air brake system. Thank you Les

.
Well Congratulations!

You may not be able to go as fast as a Class A Motorhome, but you can definitely get out in the woods and have fun. Even better that your girl is happy with the idea! Just don't wear her out on the idea because you are always working on the truck. Easy to get wound up on fixing the truck. Heck, throw a camp stove and a lantern, an air mattress and go enjoy it. THEN you have something that you both want to fix

I noticed that you are a new member, so WELCOME to the Steel Soldiers!. Be sure to take advantage of the downloadable TM's for your truck. The 939 Series are what you need for the truck. The last few numbers in the TM's (Technical Manuals) tell you what they are all about. The "-10" in the end of TM9-2320-272-10 for example is the Operations Manual (User's Guide)

The "-24" is general support manual for the M939 series truck. (There are 4 books)
The "-24p" is parts (There are 2 books)

Download all of them. That way you have them as you go along. They are REALLY DRY reading, but just thumbing through the pictures will be useful. Especially when you are trying to describe the thing under this other thing - and we won't know what the heck you are talking about. The books will solve that.

Snap a few pictures of your New-To-You truck so all of us can oggle it.
And, again - welcome to the outfit!

 

[simp5782]

Intercooler? like a universal one? Is there one everyone on here likes?

Rg31 mrap units have an aluminum radiator. Transmission air charge cooler and intercooler made into one @silverstate55 might have one near youm or I've got a few

Radiator swap is about a three job and a simple Mod. Welding intercooler pipes is more time

 

[3up]

Thank you. We plan on going the first night we live close to the dez so it will be easy.

 

[98G]

A KS RSMS truck. In my experience the KS RSMS group did a superior job reconditioning them. Contract cost was $65k per truck.

 

[3up]

Cool how do you know that? Did it get a new motor and trans? It has zero rust looks like its life was in the desert

 

[3up]

What does KS RSMS mean? Is there a way to figure out how many miles it really has on it after the rebuild

 

[Mullaney]

What does KS RSMS mean? Is there a way to figure out how many miles it really has on it after the rebuild

Readiness Sustainment Maintenance Site @ Fort Riley, Kansas

Hate to be the bearer or bad news about mileage, but military vehicles are exempt from mileage (odometer) requirements. If the speedometer is swapped out, chances are good that it got changed and started at zero. Most are low mileage, but driven by a hormone fountain in a hurry to get to the next thing that needs to be done.

 

[3up]

Cool thank you. I was hoping they would log the odometer when they did the rebuild mine shows like 42,000 or something like that total

 

[98G]

Most likely it got new gauges at reset so what it shows is what's been put on it since reset.

Not all engines were swapped. The data plate on driver side front of engine will tell you if so.

The rust proofing by KS was unparalleled.

 

[G744]

42K is ancient on a tactical. Exceptionally so.

DG

 

[98G]

42K is ancient on a tactical. Exceptionally so.

DG

Yes, but...

Figure the last civvy owner may have gently driven it quite a bit.

 

[Crf450x]

I’d definitely do a little diagnosing before firing up the parts cannon…and even if it is the ppv, you can take it apart and fix it for next to nothing rather than buying a new one. That’s just my opinion.

 

[Floridianson]

Just wondering have you looked to see / feel where the air is popping from? If it is an over pressure of 150 then you would back down on the governor to 120. Just spit balling could it be the air dryer lower unit popping off and needs to be serviced? As for the pop off valve some can be taken apart and cleaned as it a adjusting screw, plate rubber and spring. Easer if you take it apart is bring it into the shop with shop air with gages with adjustable regulator and you set your pop of pressure with the adjusting screw. Not fun but can be done. Just try and remember / count threads of where the set screw was to start. This help take some time off setting it back to specs.

 

[3up]

Thank you, it only pops off driving, its passenger side by air tanks The gauge on the dash pumped up to about 120 primary and secondary. I read here somewhere that if the horn doesn't work it will tell you it's certain valve but I couldn't find that thread again and my horn doesn't work, yes its high miles but i have a feeling its a new motor no smoke on cold start runs really good. And it was all i could afford at this time.