M35A3 power steering boost

Problem: M35A3 hard steering with the power boost system

Our fire department (located in rural East Texas) just purchased a M35A3 from Federal Surplus Property (San Antionio) along with a parts vehicle. The primary vehicle appears to be in good shape except for one thing: the steering is very difficult; not too bad at highway speeds. However, we intend to use it primarily as an off-road brush truck configured with a water tank and pump.

The power boost steering does not provide much assist (at least I think it should be better than it is). The air system gage on the instrument panel reaches 120 psi several minutes after engine start-up and I can hear the relief valve open and close so I believe the vehicle has adequate initial tank pressure. I have been unable to locate any power boost system leaks at this time.

1. What pressure should the boost (drag link and cylinder) system be operating at?

There is a pressure regulator located up stream of the drag link; a Norgren R07-200-RNKA 300 to 100 psi. I have not yet determined what pressure it is set at now.

2. Will I risk harming the system if I crank the regulator wide open (to 100 psi)?

3. What if I remove the regulator entirely and operate at the 120 psi air pressure?

Royce
8/15/2010

You can safely remove the regulator. It's not needed at the low pressure these trucks run at.
It may or may not solve your problem.

Frodo is right, ditch the regulator. Also the A3 should reach full air in less than one minute or so not the several minutes you mentioned.

Keep in mind, the air assist add-on, is never going to provide the same amount of assist as a hydraulic assisted steering system.

Do you get an air release, with a change of direction of the steering wheel?

The Torque Valve on the drag-link, senses the steering direction and switches air to the correct end of the air cylinder.

If you just sit still, and turn the wheel about a 1/2 a turn back and forth, you should hear the air being released with each change of direction.

Air assist will not provide enough assist to simply use a finger or two while sitting still, and be able to turn the wheel lock to lock, like conventional power hydraulic steering.

So, if you hear no leaks and can hear the "pfft" with direction changes, you are probably functioning to full capacity of the system.

Keep in mind that if you try to turn the wheels without moving you are placing an unworkable amount of force on the steering gear. The AIR O MATIC is designed for the 900x20 and the larger tires do place more resistance in the steering. If you only try to turn the wheel when you are moving it will not be an issue.

Hope this is helpful

RL

There is a valve mounted on the firewall that may be shut off. If it is shut, you won't be getting any air to the regulator. Ron

Turn the valve off on the firewall and see if you can tell the difference, I was the same way with our M35A3 so I turned the valve off just to see if it was actually working or if something was wrong. You should be able to tell the difference. We used ours on a 4,000 acre fire a couple months ago and it worked great, wish we had another on just like it. It might take awhile to get there but once it is there you can sure do some good with it.

the air o matic is designed to turn 14.50x20 tires. if you are not getting any power from the system, then the drag link is bad, or the system was turned off. under front fender is a line that goes from the drag link to a connection to the right of the steering box, that connection has a regulator on the back side of it between the frame and the engine. there is a small black cup at the bottom of it the screws off and on. screw it off and with the engine running, twist the knob under the cup to increase the pressure to the drag link. you should be able to feel an increase in assistance as you open the valve. if that fails to get you the desired results, then you may need to replace the drag link.

Dragging this thread out because I need some perspective on how much "assistance" the Air-O-Matic is supposed to provide.

I have an A3 and I CANNOT turn the wheel while at a stand still no matter what. I'm not talking about lock to lock, I can't turn it at all. I am a pretty strong person, I'm 6', 280lbs, and while I could stand to lose some weight, there aren't many things that I've come across that I'm too weak to do............EXCEPT for steering this ******* truck.

The truck makes full air quickly, the valve at the firewall is on, the regulator is opened all the way up, and when moving I can hear air release from the steering when I turn the wheel and return it to center. So I'm pretty sure the system is getting air.

However, under 10mph I have to put my full body weight into turning the wheel, and at a stop I cannot make any appreciable corrections to the steering no matter how much effort I put into it. I tried so hard last night that I had to stop for fear of breaking the linkage or the steering wheel. I put so much effort into backing it out of the shop, that my jacket is still wet with sweat this morning. When I got back in my M1009 to drive home, the steering felt like a race car in comparison. Now I know not to expect the same from an air system as I would from a normal power steering system, but right now this truck is undrivable as far as I'm concerned; I cannot turn the steering wheel enough to make right turns at a speed that would be considered a "safe" turning speed.

At this point, I don't think it's normal.........there is NO WAY that it is normal.

So....... for you guys with A3's with perfectly functioning steering, how much effort does it take you to turn the wheels while at a stop? Can you go from lock to lock at a stop with moderate effort?

I love the truck, but if this is normal it's going up for sale. I can put up with a whole lot, but having to make a 67 point turn just to turn right at a light is not one of them.


Thanks,
Mike

My A3 didn't have much/any assist until I screwed the frame mounted regulator in a good bit. Not sure where it was when I started or how much it has left but I screwed it in 5 or 6 turns. Now at a standstill I can turn lock to lock with a moderate effort on the steering wheel. I tried to drive it in the yard recently with no air pressure, I broke one of the plastic fittings removing the hood for sandblasting, and was unable to steer it at all without having it moving first.

renovate7 said:

My A3 didn't have much/any assist until I screwed the frame mounted regulator in a good bit. Not sure where it was when I started or how much it has left but I screwed it in 5 or 6 turns. Now at a standstill I can turn lock to lock with a moderate effort on the steering wheel. I tried to drive it in the yard recently with no air pressure, I broke one of the plastic fittings removing the hood for sandblasting, and was unable to steer it at all without having it moving first.

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Intellectually challenged question here, but just to clarify which way did you turn the knob on the regulator to increase pressure? Clockwise or counter clockwise?

it's been stated in many threads - the regulator is not necessary for the deuces 120psi system. I believe there was even a maintenance update to remove it from the equipment.

However, under 10mph I have to put my full body weight into turning the wheel, and at a stop I cannot make any appreciable corrections to the steering no matter how much effort I put into it.

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If it is up to par, you should be able to just use like one finger to turn at 10 MPH. Still, it probably will not turn easy or at all at a full stop.

Get rid of the regulator, add air tool oil to the two moving parts, should be good to go.

Yup, I'm intellectually challenged. I had turned the regulator all the way........ counter clockwise. It works now, it's certainly not "fun" at a stand still, but it's turnable.



Mike

Hello All,
Been having some tough steering as well, discovered this. Still trying to identify it and and get a replacement.
Any thoughts?

Thanks,
Jon

that is a breather hose for power steering, you would only need it if that part goes under water, I cut out the bad parts on mine and wrapped in a rubber tape and remounted it in engine compartment. You can not find that hose I looked every where

Tomcata3 I took a good long look at your duece on saturday at Appel's ( in between clips). That is a very nice truck that you have.

RECONJON said:

Hello All,
Been having some tough steering as well, discovered this. Still trying to identify it and and get a replacement.
Any thoughts?

Thanks,
Jon

Click to expand...

My truck had a hose that looked just like that when I bought it. I looked for a week to find the correct hose to replace it and found this TD7 Neoprene Coated Duct Hose but it is very spendy like $115 for 25 feet and I called the company and they would not send any length of hose less than 25 feet so you either buy the 25 feet and have 18 feet left over or you can take the hose off completely and not replace it or finally you can be like me and just use any standard 1'' ID hose as long as it has a reinforced rib to keep it from collapsing from suction. hope this helps.

AceHigh said:

If it is up to par, you should be able to just use like one finger to turn at 10 MPH. Still, it probably will not turn easy or at all at a full stop.

Get rid of the regulator, add air tool oil to the two moving parts, should be good to go.

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I haven't removed my regulator yet so do I have to worry about the air tool oil doing any harm to the regulator?

I replaced mine with the appropriate size generic rubber heater hose purchased from NAPA auto parts. The new hose is bullet proof compared to the shredded old paper wire one. Very cheap $ to boot!

Paul