Air suspension basics

[Golden_Otto_Bus]

Hey gang,

We have a 2003 Bluebird Model TC2000 with air brakes and air suspension.

I'm a bit confused on the suspension part of the system. Once the bus is off should it drop down to its lowest level in a short period or is it supposed to stay 'jacked up'? Our bus' front drops down fairly quickly and the backend stays up in the air for quite awhile.

When we stop driving at the end of the day I should bleed the air compressor tanks for moisture, correct? Then we would lose pressure and it would drop anyway.

The bus also has this button on the dash with an engine pic and a +/- sign on it. Doesn't seem to do anything but maybe related?

Thanks for any help you can provide! Cheers! J

[Sehnsucht]

Air suspension should not necessarily drop by default, in fact I would say the opposite is preferable because it means the air system is good and free of leaks. Yes over time while parked the air system is inevitably going to bleed air and the suspension will lower as a result. If the front is dropping shortly after parking but the rear is not, that implies there's a leak somewhere in the front but that's not to say it's a critical issue, just not as tight as the rear. I will say I'm actually surprised that the front axle is also air ride, that's uncommon but probably a sweet ride!

If the air system doesn't have auto-bleeders, the proper habit is to bleed the air tanks daily. There should be a cable or something attached to a pop-valve on each tank and a quick tug allows any accumulated moisture in the tank to spit out. If you make it a habit then most likely you won't notice anything but if it's allowed to accumulate then the air release will sound 'wet', or you'll be able to distinguish the gurgling sound of air and water being ejected. The point of this is moisture in the air system rusts out the air tanks and also in winter water in the lines can freeze up and render the brakes inoperable.

I can't speak to the engine related button but maybe someone with a similar model can address it. If I were to guess it may be an engine brake or high idle or even cruise control given the perceived quality of your particular bus. If it has full air ride suspension it was probably a trip bus so an engine brake isn't out of the question. Things like luggage racks and air conditioning are usually only found on school buses that were purchased specifically for field trips and sports teams and such. If so, good find!

[Sehnsucht]

Sorry, duplicate post

[flattracker]

My "new Crown" has air ride suspension in the rear. I had a problem where one side would leak down over a period of hours. I replaced a check valve in the air line going into the leveling valve (that sets the position the air bags will fill to). Now the air suspension will stay up for weeks/months at a time. It is designed to stay up even when the rest of the air system bleeds down. Their should be check valves for each wheel. Their should be a leveling valve for each wheel. The replacement check valve cost me about $20. Go there first.

[Golden_Otto_Bus]

Thanks for all the info! I need to get under there and track down that leak.

[Jsneeb]

Originally Posted by flattracker

My "new Crown" has air ride suspension in the rear. I had a problem where one side would leak down over a period of hours. I replaced a check valve in the air line going into the leveling valve (that sets the position the air bags will fill to). Now the air suspension will stay up for weeks/months at a time. It is designed to stay up even when the rest of the air system bleeds down. Their should be check valves for each wheel. Their should be a leveling valve for each wheel. The replacement check valve cost me about $20. Go there first.

Hi, i know this post was from a long while ago.

But are you able to share the part number of this check valve? The front of my bus also drops down.

[flattracker]

I don't remember the part number but I remember replacing it. What I would do is remove the suspect check valve and take it to a Fleet Pride store or a Napa store and ask for one like it. Be careful when you remove the part in case your air ride has air built up. If the air system has air built up and you disconnect the check valve the suspension could collapse down on you. That sudden lowering could be 6 - 8 inches and if your head is close to the floor you will run out of room. If you adjust the leveling valve, same thing, if you change the level the suspension may drop.
Sorry about not remembering the number, but I do remember I got the part on ebay, so that is another place to look.