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Old 04-08-2019, 05:22 PM   #1
Mini-Skoolie
 
Join Date: Sep 2016
Location: TEXAS
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Year: 1999
Chassis: MVP RE
Engine: 5.9 Cummins
Air bags or shocks

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.
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Old 04-08-2019, 05:34 PM   #2
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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?
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Old 04-08-2019, 05:54 PM   #3
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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.
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Old 04-08-2019, 06:19 PM   #4
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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!!
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Old 04-08-2019, 06:53 PM   #5
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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.
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Old 04-08-2019, 07:36 PM   #6
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I totally suspect a bad leveling valve or linkage to the valve.
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Old 04-08-2019, 08:34 PM   #7
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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.
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Old 04-09-2019, 02:08 AM   #8
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Quote:
Originally Posted by Brad_SwiftFur View Post
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.
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Old 04-16-2019, 05:00 PM   #9
Mini-Skoolie
 
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Originally Posted by Johnny Mullet View Post
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.
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Old 04-16-2019, 06:26 PM   #10
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Definitely a Jake-Leg job!
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