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+--- Thread: What causes the leans? (/showthread.php?tid=861)
What causes the leans? - davidbrady - 04-18-2017 09:59
Folks,
A while back Hector Duplichen did a brilliant animation of the air suspension used in our buses including level-low. He made it public domain. I can't seem to find it but I'll continue looking. In the meantime the attached article may be helpful - skip the text and go right to Hector's pictures. All of the diagrams in the article are Hector's. You can see there're five norgren spool valves at the rear of the coach. Rather than chase leaks to specific valves, most folks simply replace all five when they get the leans.
Ernie, Joe Cannarozzi, is a traveling Prevost mechanic. I'm sure a quick call to him would point you in the right direction. His recommendation to me is: if the bus is leaning, replace everything on that side; i.e., all norgrens and all air bags, and if the bus isn't leaning, do nothing.
Hish informs me that Hector's webinar, "Prevost Air Systems and the Leans", is available on the Prevost Car website. The website does require registration but registration is open to Prevost motorcoach owners. I'll get the details and post later.
RE: What causes the leans? - ERNIEE - 04-18-2017 19:40
Thank you for the file, David.
RE: What causes the leans? - ERNIEE - 04-19-2017 18:56
I contacted Joe- he was in Abilene on Monday and back in Chicago now. Aired coach up and turned it off. It has maintained her level for close to two days. I thought my X was fickle
RE: What causes the leans? - cmillsap - 04-19-2017 21:12
(04-19-2017 18:56)ERNIEE Wrote: I contacted Joe- he was in Abilene on Monday and back in Chicago now. Aired coach up and turned it off. It has maintained her level for close to two days. I thought my X was fickle
Ernie,
Air leaks in fittings and line connections don't fix themselves. Sounds like a sticky valve in the air system. I like what David does to exercise the air system each time he exercises his bus. If it happens again, try doing what he does. Use the level-low to raise and lower the bus at all three positions a few times. This may free up the sticky valve(s). Sticky valves are more likely to happen on a bus that has sit for an extended period of time with an inactive air system.
RE: What causes the leans? - travelite - 04-20-2017 16:13
Too bad you missed him Ernie. Joe's a great guy. He's a wizard with Prevost air systems and he's very reasonable money wise.
RE: What causes the leans? - ERNIEE - 04-20-2017 20:00
He said he will return in the fall. Strange, though on my lean- coach has stayed level for 2 days without leaning and I have 100+ in the tanks.
RE: What causes the leans? - davidbrady - 04-20-2017 20:44
Ernie,
When the key is turned off the norgren valves at each corner (right rear, left rear, and front) isolate the air bags trapping air between the valves and the bags. Your tanks can drain down to zero and the coach should still maintain its ride height.
RE: What causes the leans? - CC_Guy - 04-28-2017 09:23
If you print your air drawing large enough you can get a good since of air flow and valve functions. To help troubleshoot the problem you can do a couple of things.
After turning off the key, dump your aux air. This will speed up the leans if it's the level low valve.
Raise the tag to isolate the tag bags and tag valves from the problem.
If it only leans when it's cold you should suspect a push-on fitting. The fitting has a sealing o ring that tends to leak when cold as they age.
RE: What causes the leans? - ERNIEE - 04-28-2017 19:31
since I had the front bags replaced, all is well