New m932A2

[Retiredwarhorses]

New M931A2

Picked up the new M931A2 yesterday....fired right up, no jump required.
aired up the one flat tire capped of the broken/missing emergency valve and drove her home....the only issue was the primary and secondary tanks were going to 150psi and blowing off' I played with the ctis and something I did fixed it and the issued stopped, tanks went to 120 and stayed for the remainder of the drive and have been fine since. The truck has 4hrs and 148 miles on it, the BII box was full of all brand new goodies...air hose, 20ton jack, tools, Brand new in the wrapper -10, 2 new in the box US stamped locks with keys, lug wrench, trailer power cable etc....interior is all NOS, both batteries brand new.
the truck was reset at Camp Shelby Mississippi in Nov of 2011 and then parked, then sent to Camp Roberts calif . The 8.3 runs and drives way nicer then the 250 cummins IMHO.


Pics to come....

 

[Suprman]

You have a bad air safety valve you need to replace it. It is supposed to open at 60psi but it sounds like it was sticking. You are lucky the air dryer safety worked I have seen them gummed up also.

 

[Retiredwarhorses]

It appears all is working correctly, I figured one or more valves were frozen due to none use, but with air pressure came un frozen...do you think the safety valve is still a issue? How can I test. I don't have access right now to psp or TM
everything airs up fine, gauges on prime and secondary tank build to 120 then stop and fluctuate from 90-120 while driving arounds as normal. Where is the safety valve on the 931?

 

[Suprman]

It is called a pressure protective valve it is on the passenger side by the air tanks if you are standing by the drain valves it is back and a little left. They are like 30 bucks if it stuck once chances are it will stick again.

 

[Retiredwarhorses]

I thought so, at least on my m923 its in that location, the only one I found was literally next to the dryer assy for the abs...it's not in the same position as the m923...on my 923 its right off the bottom tank, it was broken off when I got the truck as a,fork lift tried to move the truck and broke it. I assume this the correct one?
also can you explain the 65psi pop off pressure? Would it not pop at 120psi? I know we have primary tank, secondary and wet tank and spring brake tank. I will get my head into the -10 when I get off duty.

 

[Suprman]

You said in your first post you built pressure to 150 psi then the air dryer safety relief opened which is exactly what is supposed to happen in that situation. The governor is past the ppv so the pressure will just build. If the valve stuck once it will do it again. They look like this.

 

[Retiredwarhorses]

Thanks bro....i will climb under tonite. Can they be cleaned...or just replace it? This is a standard valve, any civy part numbers....napa?

 

[Suprman]

No it needs to be replaced it is a standard pr2 65psi pressure protective valve. Napa sometimes has it I have better luck with fleetpride. Both of my a2s are rebuilds one 2010 and one 2012 and they both had old ppvs that both went bad the first week. Both had bad shocks too its a much nicer ride with a new pair of shocks. I usually drive around town in xc mode too make the ride nicer also.

 

[jonesal]

Where are the pictures? You're killing us.

Al Jones
'84 M923

 

[tobyS]

Suprman is probably right about replacing the valve. But there is always a fresh lubing with Marvel Mystery Oil, that has helped sticking valves in the air systems I maintain. Not sure why there is no air lube on them, but opening the top most fitting would allow a bit of the oil in to loosen it up...or take it out and clean it, replacing old grease with new silicone grease. And you can examine the damage of rust on the spring or plunger to know if replacement is necessary.

It does seem that it would be a modulating valve for kicking in or out the compressor that was malfunctioning...which may be what suprman is describing, but I don't have an A2 myself to look.

 

[trooper632]

whats the best way to lube the air system, and how do you know it needs to be done

 

[Retiredwarhorses]

Yea, is it like muffler bearing grease? Lol

 

[tobyS]

Compressed air is prone to moisture, which eventually washes out grease lubricants and collects dirt in what remains. Seals and tight fits (like valves with return springs) don't work with much debris of course.

So one installs an oiler, which drips atomized oil into the stream of air, that lubricates but does not last and must be replaced/fed/consumed. The longer fix on the truck is first a new part, second a rebuild that probably replaces the spring and puts in silicone grease properly, not in too much excess, and third, open a fitting and squirt in air tool oil (Marvel Mystery Oil is one). Sometimes it softens old grease up and works properly for a long time.

I have not researched how the pump is lubed OR if there is a self lubricator in an air line, I'm just talking about the pressure system valve.

 

[Retiredwarhorses]

In the quick ref parts cross reference, I found NAPA part number MBI KN31000, while it looks a bit different, I assume this will work. The specs are it opens at 65psi, closes at 45psi.....I think the one pictured is adjustable? I know the one on the truck now looks just like the one Superman post the pic of....plus it is safety wired to prevent further tampering.

 

[Retiredwarhorses]

Well, the little gremlin is back this morning....I took the ppv off and cleaned it up, put some air tool oil in it and blew it out....does the air blow out at the base of this unit?i assume its wired cuz it's adjustable?

im confused...the -10'shows the safety valve located on the inlet side of the wet tank, blow off at 150psi...the ppv allows pressure to build to 60-65 psi before allowing air to build to aux powered equipment.item C is blowing on page 1-58, the ppv is item E, its on the inlet of the wet tank...

 

[Suprman]

I don't remember the part number but it is a standard bendix pr2 pressure protective valve. The tm does not recommend any lubricant for the air system. Remember anything you put in will find its way into the tires via ctis. Jeff in sparta said you can put some air brake system alcohol in if there is moisture in the system. If the valve stuck once it will stick again they are inexpensive and can cause expensive problems when they fail. The wire on it prevents the open/close pressure setting from being changed. You can get one that is not preset and set it yourself too.

 

[Suprman]

The 150psi blow off valve is on the air dryer. It's there so when your valve sticks you won't blow something up.

 

[Retiredwarhorses]

Well, I will get it replaced....do I have a possible governor problem, I mean, the tank airing up to 150’ should the governor not stop them at 120psi or so?

and now...just in the past few minutes...the CTIS,assy in the cab is just leaking air while truck is off....

 

[Suprman]

The governor is on the firewall towards the passenger side. There is a cap on the front of it (facing drivers side) that unscrews. Sometimes they are tight you have to use pliers for the first turn. With the cap off you will see a threaded rod coming out with a set nut. Loosen the set nut and you can adjust the governor pressure. You can adjust it with the truck running if you like, each time you make an adjustment you should pump the brakes to cycle the compressor and then it should build to the adjusted pressure. Once you have it set lock the nut back down and screw the cap back on. The primary and secondary pressures will never exactly match I set the lowest one to 135.

 

[Suprman]

The governor is past the ppv so if the ppv doesn't open the governor can't do it's job.