Low air buzzer going off when turning the wheel

[Coalman]

Sorry fogot to put ,I have an m35a3 I have a problem with the low air buzzer going off when turning the wheel. (before somebody jumps in and says use the search I did ) I went and put marvels mystery oil in the air intake on the steering box and also in the air assist cylinder behind the axle I also tuned up the regulator on the frame, took the air assist cylinder apart and cleaned it, checked it on the bench, and it seamed OK Now what should I do next is my question? Any help would be greatly appreciated Thanks Kevin

 

[porkysplace]

How low is the air pressure droping on the gauge ?

 

[Deuce007]

Mine has also had this problem for a long time and I haven't been able to find a solution yet either. I have an idea that mine might be because of the priority valve leaking. That is explained here : http://www.steelsoldiers.com/showthread.php?103324-Replacement-Of-The-Priority-Valve-On-The-M35A3 I tried to fix it several months ago by putting some ultra black silicon around the lip of the cover but in heinsight I think that might have caused it to gum up. I am not certain that is the problem but I think it might be. Just out of curiosity do you know if your priority valve leaks?

 

[Coalman]

The only time the air gauge goes down fast or the buzzer goes off is when I turn the wheel and hold it there. You can see the gauge drop. This only seams to do it when the truck is at idle or low rpms like when you are parking

 

[porkysplace]

Get soldier B to turn the wheel while you search for the air leak . Most likely either the cylinder or a valve leaking.

 

[Coalman]

It is not the cylinder on the back of axle.I Had that apart and cleaned and the reinstalled it. It does it in both directions so that should take out the possibilities of a hose???

 

[rosco]

The same leak, is probably occurring, when the engine is running faster, but the compressor can better keep up with it then. The priority valve may be the problem too. Sometimes the valves can be just taken apart and cleaned. They get gummed up. Also I have found that its best to lube them with a silicone based lube. Sometimes you can disconnect the line, up-stream from the valve, and use a spray can with a straw to insert some lube directly into the line. Air can be a significant issue - or the loss of it. Those DOT guys perk right up, when they hear that buzzer go off. They get cranky and hard to deal with.

 

[runk]

On a M35a2 with the air assist installed, when you are maneuvering a lot at idle (in my case to get it parked in the back yard), the air assist uses air faster then the compressor can keep up with. The air exhausting out when you switch the direction you are turning is normal, as is the exhaust if you hold it against the stops in either direction. With the truck off you can bleed the air system down pretty fast by turning the steering back and forth a bit, at least down the to the pressure the pressure closing (or priority) valve is set. The valves are usually set about the same pressure as the low air buzzer. I know if my buzzer goes off, the steering is about to get a lot harder !

 

[Coalman]

Thanks Runk, it never did this before though. It just started setting the buzzer off That is why I am a little concerned Thanks Kevin

 

[runk]

If it's a new leak (leaking all the time, not just when the steering wheel is moved), the most likely cuplrit (again on the M35a2 install, looks like the a3 setup is the same based on the TMs) is the useless, cheap, crappy regulator in the air assist system. If you have one (the latest installations deleted it), it is mounted on the inside of the frame rail in the air line that supplies air to the drag link valve.

 

[Coalman]

Only when turning the wheel

 

[runk]

Well, that at least narrow the possibilities for leaks. Has to be the drag link, hoses and fittings to the cylinder, or the cylinder. Have to get down there with some soapy water and get the joints wet while someone else moves the wheel. I'd do it with the engine off so you can hear, rear wheels chocked for safety. If you run out of air, run the engine for a bit. You can also rig a hookup to the emergency air glad hand from an external compressor to get air to the system without running the engine.
Let us know what is leaking.

 

[doghead]

I can not back up more than about 100 feet with my trailer in my driveway before mine will do the same thing. I think it is normal.

 

[Coalman]

Mine is a real bear to try and steer when you are moving slow. That's why I think somthing is wrong. I can hardly make a turn at an intersection without going over the lines .

 

[AceHigh]

Coalman, I first had this problem on my A3 to the point I could not drive it anymore- it started gradually at first, and I did all the air assist maintenance stuff, but it still get worse.

Finally I was tracing the air lines, found the priority valve (didn't know what it was at the time though) and hit it with a hammer. Suddenly it made a loud noise and almost immediately air built up. That solved the problem for about 6 months, then it came back.

 

[rrrr]

When I installed my air o steering I left off the regulating valve based on the recommendations of the forum and the installation instructions indicating it was optional. Works great over the last year with no issues. (edit for content)

 

[runk]

Its always been hard to steer, or that is new with the low air ?

If you've got a leak, that means that the air cylinder isn't getting enough air.
If you got a stuck valve in the drag link so that it is exhausting air when it shouldn't (or all the time), then the cylinder won't build enough pressure to be useful.

The drag link is basically a clever assembly of air logic valves that sense when the drag link is being compressed (steering one direction) or stretched (the other direction). When you're turning left it supplies air to the cylinder to push the steering left and vents the other side of the cylinder, when steering right it switches cylinder sides. When the steering is still, I think it vents both sides but haven't put a gauge in line to see. It is a pretty cool setup and I'd like to open one up, but I'm not willing to play around with the one I'm using!

So, still need to know where the air is coming from. Leak = fix it; stuck drag link = lubricate and exercise. There is a good thread on how one member fixed his stuck drag link with lubrication and exercise.

 

[runk]

Removing the priority valve (pressure closing valve) is a very very bad idea !

It is there to make sure you still have air assist to the brakes if the air assist steering fails. If you have a big leak in the steering (or any other air system problem) and the air system drops below the set point (about 60 PSI) it closes off the steering supply so any remaining pressure can be supplied to the brakes. When my regulator failed, I was very glad the valve shut off the massive leak and I still had brakes !

The regulator in the air assist system is junk and not necessary, and should be removed. But, don't remove the priority (pressure closing) valve it is an important safety component !
replacement priority valves are available from Erik's-
http://www.eriksmilitarysurplus.com/prprva28pr.html

 

[maccus]

I can not back up more than about 100 feet with my trailer in my driveway before mine will do the same thing. I think it is normal.

Doghead is right. It is normal when turning a lot for it to go into the alarm condition..