Draining Bus Leveling Air ???

[chris4905]

How do I drain all the air from the leveling system in a 4905.

I'm doing an engine change, started disconnecting to remove the old engine this afternoon.  I want to drain all the leveling air so the bus settles on large wood blocks.  I've done everything I can think of except drain the tank in the middle of the doghouse.  I can't get under there and drain it, cause if it settled, I wouldn't be able to get out.

Is there another way of draining the leveling air?  As a last alternative I could disconnect the lines to all the leveling valves, but I sure hate to be under there when I do that.

Any suggestions?

Chris Christensen
1974 GMC 4905-739 (out w/ the 8V71 & Spicer ----in with the 6V92 and Allison V730)

[Buffalo SpaceShip]

Chris, the system is designed to "stay up" even when the air has all leaked out. However, due to leaking bellows, leveling valves, check valves, etc., many old coaches don't stay up indefinitely. Some can even leak down in a few hours. On my coach, the back end leaks down in a few days, but the front stays up for weeks. So how long does each axle of yours typically stay up?

The only surefire way to get yours to leak down "while you wait" is to pull the check valves off the leveling valves... but like you say, that's a dangerous prospect! If you properly place the wooden blocks right under the rubber bumpers on the suspension system, and they're sized for the job (between 3" and 3-/2", IIRC), the coach should stay in the "road-ready" position. But I still wouldn't risk it being under there to pull the valves without a pit.

HTH,
Brian Brown

[chris4905]

Brian, thanks for the reply.  My left-rear settles in about 4-5 days.  The right-rear and front will stay up for a good month, if not longer. 

If I don't settle the coach I'm afraid the air will dump when I start to remove the engine and the coach will settle RAPIDLY before I'm ready.

Thanks again for the input Brian.

Chris

[Don4107]

If you don't have them, you should build a set of run up blocks.   These are very sturdy blocks that will hold the weight safely.  They raise the bus enough that you can move around under the bus with the airbags all the way deflated.  There are plans around for them on this or the other bus boards.  Just be absolutely sure they are strong enough.  Here is one way to build them.

http://www.thefamilybus.net/projects/blocks/

Don't forget to  make sure the coach can't roll off the blocks.

Once raised and secure you can then drain the air tanks.  Disconnect the leveling valve link to the body and manually deflate by pushing up on the leveling valve arms.  It happens slowly.  They have a built in delay.  I did this to replace a damaged front radius rod mount on my 4107.  If you don't want to be under the bus when you lower it, a string could be rigged to operate the leveling valves.  This way you don't need to break any air lines.

Be safe!

[Dallas]

An alternate way to lower the bus without getting underneath would be to put a hydraulic jack under it and raise the body.
When you do that, the leveling valve will be pulled up allowing the air to discharge from the bags as the valve tries to lower the body again.
Don't put the jack under the axle, that will compress the axle/body dimension and make the valve add air to the bags.
Either put the jack at a lift point on the body or between the body and the axle.

What ever you decide to do, BE CAREFUL! we want you back here again!

Dallas

GO BUSSING!