'81 Prevost kneels w/o kneeling valve

[bobofthenorth]

The front end of my '81 goes down very quickly after the bus is shut off.  For sure it's down in 6 hours - probably less.  The rest of the system holds air for days.  I've read bits and pieces about the levelling valve - is that where I should start looking?  And if so, where is it and what does it look like?  I've got a local shop with a pit booked for the weekend after next so I have a few days to get ready for this project. 

[H3Jim]

Get 'cher spray  bottle of of soapy water and just start spraying everything that looks like an air line or valve or supension bags.  You might have to look closely if its a slow leak, but they will show. Not much else to do other than maybe be at a place where there are parts to buy an put on at the time.  It could be the bag too, the rolling lobe that Prevost uses (not sure if your bus has them or not) typically start leaking out the bottom.

[Skykingrob]

Hi Bob
I have a 91 LeMirage XL that does just the reverse.  But yes, the kneeling valve is located in the area behind the spare tire storage and in front of the front wall of the baggage area in an area where the tie rod runs between the two front wheels. It is easy to spot. As was suggested, get a spray bottle of liquid detergent and water to spray the hoses/valves.  Call Prevost to get a replacement and have ready. If it ends up not being the valve, Prevost will take back minus shipping.
I bought the replacement for mine, cost 70$ new including shipping, just haven't been able to replace because no pit to work on it. Should take about 1 hour labor to replace per Prevost shop manual. Replacement parts are available to rebuild yourself but not much savings over a new valve.
Good Luck

Rob
91 LeMirage XL
Missouri

[NJT5047]

The best leak detector that I've found is children's bubble blowing liquid.  Get it at Wally World.  Cheap, and has more "cling" to items.   While soapy water will work on very small leaks, it'll blow away from some larger leaks. 
My vote for the most common leaking item goes to the airbag.  Obviously, the most expensive part.   Still, the leveling valve, check valves, regulator, and any plumbing related to the front ABs could cause also. 
Might try isolating the airbags and see if they stay up.  They are a good bit of work and expense to replace.  If they are original, they are ready to be replaced.  If not, you wouldn't want to replace a good airbag.  Front airbags operate in the 60 lbs range and that would be a good setpoint for an airbag test.   An airbag should hold air for weeks.  Even less may not be an issue.  Unless you want to level with the bus suspension.
Cheers, JR

[Ace]

I experience a similar situation with my H3 except it only does it some times. When I turn everything off, after an hour or so the RF will go down while the rest stay up. If I start it up, build the air up to normal and shut it off again, it all stays up but eventually (very slowly) goes down and equally.

Beats me!

Sometimes it goes down first, and sometimes they all go down the same!

The kneeling feature works very well and one thing you DON'T want to do unless your looking for an absolute butt squeeker is, you DON'T want to accidently hit the kneeling button while doing 65 mph on a busy Interstate 95 at 9pm. Don't ask how or why but it happend to me recently and it wasn't funny! Once you hit the button, there is NO getting it back up untilk you stop and you better stop quick or the body will soon be down on the tire and if your rolling, well you get the picture!

"Definitely a drawer browning occassion"! 

Ace

[buswarrior]

Hello Ace.

That kneeling feature should be locked out with the parking brake released.

Maybe something removed during stripping, or non-functional when you got the bus.

See if your schematics show something to inhibit the kneeling circuit.

Probably not the best situation having a bomb like that primed on the dashboard!

happy coaching!
buswarrior

[H3Jim]

My bus kneels when I'm moving if I press the button, however it goes right back up when I stop pressing the button.  I don't have to wait until it goes all the way down.  I use the highboy feature on the same button to lift the front high enough to get past obstacles when I back into my parking spot.