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Old 04-08-2019, 05:22 PM   #1
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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
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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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Old 04-16-2019, 06:57 PM   #11
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Quote:
Originally Posted by budbud7 View Post
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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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.
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Old 04-16-2019, 06:57 PM   #12
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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.
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Old 04-16-2019, 07:07 PM   #13
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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....
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Old 04-16-2019, 07:12 PM   #14
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Quote:
Originally Posted by ~Pat~ View Post
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.



Quote:
Originally Posted by johnbloem1974 View Post
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.
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Old 04-16-2019, 11:42 PM   #15
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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.
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Old 04-17-2019, 12:51 AM   #16
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Quote:
Originally Posted by budbud7 View Post
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?
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Old 04-17-2019, 05:49 PM   #17
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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.
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Old 04-18-2019, 12:58 AM   #18
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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?
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Old 04-18-2019, 09:40 PM   #19
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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.
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Old 04-20-2019, 04:35 PM   #20
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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
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