Air bags or shocks

[budbud7]

I have a 1999 Thomas RE with 5.9 engine. I think either the air bags and/or the shocks need to be replaced on this bus. Two years ago when I bought the bus the school bus mechanic said that the suspension was ok. But it just look like the tire is too close to the wheel well. All of the seats are out except 7 up front.

The bus seem to drive ok but I'm not a professional. Look at the attached picture and please tell me what you think. The bus does not have leaf springs, just two air bags and two shocks in the rear. The front have leaf springs.

[ermracing]

The shocks don't hold the weight of the bus, the springs (leaf, coil or air) do that. It may not be the bags, but there is a leak in the boat somewhere.... Do they pump up after the bus is running? If they do, how long does it take for them to drop after it's shut off? Can you hear the leak?

[Brad_SwiftFur]

Start the bus. Let the air system charge. Suspension air bags should inflate when air pressure reaches 80 (maybe as low as 60).


If the air pressure reaches 100+ and the air bags are still flat, you have a problem to diagnose. Any hissing air pressure is probably bad, but most parts are reasonably easy to fix. Suspension "leveling valve" is a fairly common failure and easily replaced.

[budbud7]

I have never heard any air leak. But then I have not been seeking one. The height does not change when the system is fully charged. I will charge it up and get under there and search. Also I will check out the leveling valve. Most likely its inline, near the bags. Is the valve electrical or purely mechanical?

Right now, the ground in my part of Texas is saturated!!

[ermracing]

The leveling valve on ours is between the bags, to the rear of the diff. Pretty easy to spot once you get under there, just follow the levers and stuff. Hopefully it's something simple like that.

[Johnny Mullet]

I totally suspect a bad leveling valve or linkage to the valve.

[Brad_SwiftFur]

Either the leveling valve (or associated pieces) need some work, or perhaps the leveling valve isn't getting air pressure - don't overlook that possibility.

[Native]

Originally Posted by Brad_SwiftFur

Either the leveling valve (or associated pieces) need some work, or perhaps the leveling valve isn't getting air pressure - don't overlook that possibility.

Good point. We had to replace the valve that comes out of the tank and feeds the air springs. Ours was filling up every once and a while. It was nice when full, but we experienced vary nasty jolts when the rear axle hit the bump stops.


So, there is the compressor, the tank, the valve on the tank, the air lines, the leveling valve, the self-adjusting arm that attaches between the rear axle and the leveling valve ... and the air springs to be examined.

[budbud7]

Originally Posted by Johnny Mullet

I totally suspect a bad leveling valve or linkage to the valve.

Sunday I was able to get under the bus and I did find a valve and some linkage. It appears that 1/4" rod with 1/4" rubber tubing makes up the linkage. The rubber tubing is broken up. Its attached with small hose clamps. Do you know if this is a stock arrangement (the hose/hose clamps) or is it a temporary fix.

There still might be an air leak because I didn't get that far in checking things out.

[Tango]

Definitely a Jake-Leg job!

[Brad_SwiftFur]

Originally Posted by budbud7

Sunday I was able to get under the bus and I did find a valve and some linkage. It appears that 1/4" rod with 1/4" rubber tubing makes up the linkage. The rubber tubing is broken up. Its attached with small hose clamps. Do you know if this is a stock arrangement (the hose/hose clamps) or is it a temporary fix.

There still might be an air leak because I didn't get that far in checking things out.

Originally Posted by Tango

Definitely a Jake-Leg job!

I've seen more than one truck come like that from the factory! Replace rubber tubing, and you're back in business.

[~Pat~]

If an obvious break like what's in the picture is found I would surmise someone got tired of messing with the airlines and crimped the line. Your back airbags may have a hidden Schrader valve somewhere.

[johnbloem1974]

That break where the black hose is does not hold any air. It is simply the flexible piece to hold the actuator arms. You may not actually have a leak. It could be just that the arms are not working properly. Replace that piece to get the arms li ed up properly and you may be in business!

John

Edit: Derp! Did not take the time to read the previous posts... sorry for repeating....

[Brad_SwiftFur]

Originally Posted by ~Pat~

If an obvious break like what's in the picture is found I would surmise someone got tired of messing with the airlines and crimped the line. Your back airbags may have a hidden Schrader valve somewhere.

Most don't have Schrader valves, the leveling valve does that job. On some aftermarket pickup air bags and air shocks, that's another matter.

Originally Posted by johnbloem1974

That break where the black hose is does not hold any air. It is simply the flexible piece to hold the actuator arms. You may not actually have a leak. It could be just that the arms are not working properly. Replace that piece to get the arms lined up properly and you may be in business!

John

John's got it right, the rubber tubing on the linkage does not carry any air pressure, it's simply a cheap way to attach (and allow for adjustment of) the rods. And yes, it probably came from the factory this way.

[budbud7]

Just from a review of my pictures, it appears that one of the air bags might have a small hole in it. I didn't see that when I was under there. I'll get a closer look when I get time and its not storming here.

[Native]

Originally Posted by budbud7

Just from a review of my pictures, it appears that one of the air bags might have a small hole in it. I didn't see that when I was under there. I'll get a closer look when I get time and its not storming here.

In the pictures, your air bags do not look deflated. Do they flex back when you touch them?

[budbud7]

Originally Posted by Native

In the pictures, your air bags do not look deflated. Do they flex back when you touch them?

Yes, at least the one that I touched. I will check on parts tomorrow for price and availability. Then, when I get the time, I will attempt to repair it. Most likely someone will have to instruct me in the proper installation and adjustment.

[Native]

Originally Posted by budbud7

Yes, at least the one that I touched. I will check on parts tomorrow for price and availability. Then, when I get the time, I will attempt to repair it. Most likely someone will have to instruct me in the proper installation and adjustment.

If it presses back it probably has air in it. That would mean your system is at least partially fuctional. Your pictures really point to the rubber tube as the problem, or at least one of them.


What are the parts for which you looking to get prices and availability?

[budbud7]

Got a chance to ck on part prices today. $116 for the valve kit and $175 per air bag. I will get back under there for a closer look at things before I start ordering parts. I might be able to replace the broken hoses. I also need to know how it works in order to adjust the linkage.

[Dirtdoctor]

That photo!!! Bwahahaha Suspension, brakes and tires are life savers- you screw something like that up, get in an accident and you will go
To jail. The reason commercial trucks are highly inspected is to prevent accidents from failed parts etc. take your bus to a truck mech ic and have them go through it and have them go through the DOT inspection and FIX anything not within specs. That is the responsible thing to do.
Cheers
Commercial driver since 1978