Wednesday, October 31, 2012

Air Brakes And Other Mysteries of Bus Ownership

Yes I said mysteries.  I have never had any exposure to air systems on a vehicle.  The bus was in a warehouse for a couple of months and it was time to move it.  The Bus had operated just fine when I parked it there and now it would not move.  So I have to figure out why.  The bus has a on board compressor that operates various functions of the bus.  There are air bags that provide a smooth ride down the highway.  There are valve that are attached to the engine that get actuated by compressed air.  There are three air tanks on the bus.  And last but not least the brakes work on air.

So why won't my bus go.  The air system is not building up air pressure.  There is a leak.  Without air pressure the brakes will not work.  There is a fail safe on the bus that locks up the rear wheels when there is no air pressure.  Therefore the bus will not move.

At first I thought it was the brake cans.  These are devises that move the brake in and out.  They were not the problem.  After a lot of searching I discover that a air relay valve was leaking.  This is a 1960 bus and I was worried that I would not be able to find parts.  It turned out to be no problem in that these air systems have been used on trucks for years and they are readily available.

Of course the valve is in a place that I can not reach.  It took me almost a complete day to get the rear wheels off.  Then jacking up a 21,000 pound bus required a special jack that i did  not have.  Even after jacking the bus up it was a tight fit.  So I hired a skinny mechanic.  He got the part off and out the door I drove.

I am glad in a way that the bus had this problem.  Now I know that I can get parts for the bus.  I know that the systems are not obsolete and I now understand a lot more about air brakes.