Another Air Question

[USMC46]

Have a 2004 Durtch Star. It has been parked (on jacks) for a few months (in Corus Christi). We are loading it in preparation for full timing for a spell. While it has been sitting (jacks up), I notice it has been settling down to a lower height, and when started up, raises back up to normal ride height. I think that is normal.....But...how long should it stay at normal ride height once the engine is shut off ? Does that time vary depending upon outside temperature (it seems to lower quicker in cool weather). It does not take long to raise back up when the engine is started, and the air brakes seem to be working fine on the road. Do I have a air problem..., or is this normal ? Thanks for any comments.

[Ray_IN]

The air springs should remain inflated for at least an hour. This means you do have small air leaks in the compressed air system though. The way to find air leaks is to fill a spray bottle with a 50/50 mixture of liquid soap and water, agitate, crawl under your coach (block under frame for safety) and spray anything that looks like it is a compressed air line or air spring.

One culprit can be the "spitter/purge valve" on the air dryer housing. It can become fouled with oil N water, keeping it from closing completely. This pdf shows the purge valve and air dryer details for a Meritor dryer system: http://www.meritorwabco.com/MeritorWABCO_document/tp97101.pdf