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Leaning still…..
Hi all,
The leaning has not been resolved, entirely but it happens over a longer period of time…..overnight.
Changed the 3 way (5 port) valves in the rear on both sides, new 2 way(3 ports) in the rear as well- 4 of them. I have put a new 3 way upfront and a new 2 way on top of it close to the 4 relay stack in the compartment under the driver.
Are there any more 3 way valves that I missed ?
Something has been bugging me for a while now….When the bus was as WW Williams in Grand Rapids to get the service and all the rear 2 way valves changed (easier for them to do with the bus in the air) , the mechanic said that one of the 2 way valves in the rear (most forward one on driver side, above the tag, he called it the inversion valve), had to have the airlines coming to it reversed because according to the diagrams he had from Prevost, it was plumbed wrong on the bus…..he switched the airlines top and bottom on that valve to make it correct…..
I drove it back fine, stayed up and level during drive, everything seemed to function properly but now I am wondering if that airlines reversal he did has something to do with the bus lean towards the curb side after it has been parked for a while.
Thoughts ?
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12 Replies
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I had the same problem when we first got our coach it leaned to the right and it ended up to be a bad tag air bag, When the rubber would start rolling when I dropped the bags for level low it would leak and when it was in ride position it did not leak, It took me a bit to finally find the leak, sense then i have changed all the air bags now it stays put. you can see the cracks in pic. all the bags were Bad.
Jeff and Lindsay
91 Marathon XL -
Mine still leaned after Norgrens and airbags until I changed the R-12 that controls the tag brakes. The pilot air to that R-12 is the air to the tag bag. If it leaks you will still have the leans.
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Marius
Go into your steering bay and start checking the connection in there with soapy water. If that tank in there gets below 35PSI the tags drop and for some reason the right side first or at least it goes down further. Does the pressure gauge on the dash go down as well? If so check the connections to the back of the gauge for leaks and also in the front (tire well) bay on the ceiling. That is where the lines come out from for the dash gauges. I know on mine those connections and soapy water looked like a bubble show.
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The air in main tanks with gauges on the dash are holding air above 100psi for the second day now.
The Aux system that is dually fed by engine compressor when running and the 12V compressor is setup for 45 to 65 psi and is holding air pretty decent. It will drop down to 45 psi in about 5 hours and in about 6 minutes the 12v compressor will build it back up to 65 psi.
I did check with the bubble solution and an Inficon everything I can under the driver. Don’t see anything there.
I will have to look at bags it seems and that R-12 pilot valve. The bags were put new in 2009…..I would hope they are not failing already….
Any thoughts on the reversed air lines ( top and bottom) in the “inversion” valve that the mechanic did in the shop ? Should I get those lines back the way they were before ?
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When you put the new air bags on did you get rid of all the push fittings? And go to compression fittings? also check all the fittings to air bags for leaks, A leak at air bag fittings won’t affect air pressure on aux tank, After I replaced all air bags I had 1 leak in right rear drive bag the one behind rubber flap in front of drive axial it was hard to find but I did. I put together a box of good compression fittings different sizes and some 90 degree fittings, got tired of going to truck supply for fittings.
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MAGAV65,
Have you replaced check valves on your AUX. side ?
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No, did not replace the check valves on Aux side…where are they ?…and is the 45 to 65 psi air in the AUX system holding the bus up ?
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At the stated aux pressures the bus will not be able to level itself because the air bags will have higher pressures.
If the “leans” are isolated to one area consistently the only real way to rule out air bags as a potential source of a leak is to pressurize each individually and verify they hold air. If they do hold air then move upstream one device at a time. Chasing leaks is mind numbing, tedious work that requires a lot of patience.
On your vintage coach, if has not been modified with the service bulletin change, will dump air in the tag axle air bags once aux pressure drops below around 35 PSI.
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After mutch frustration with the rear leans,I tied the tag and rear air bags together and dissabled lift chambers. Stays up all winter.Get a set of French air schematics from Prevost and have fun. I have never needed to lift the tags on this 40 footer.
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They were talking check valves there is 1 on each height control valve that I replaced all 3
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I would recommend you buy an Accutrac sensor. ($320) . If you have a leak and the coach is totally supported so you can get under it, the Accutrac will reveal the leak in very short order. If gauges are leaking, etc., it can determine exactly where and provide an estimate of the leak based on its’ sound.
The expenditure seems like a lot perhaps but this device will save hours of time. It can detect a 1 oz leak of refrigerant that is escaping over a twelve month period. Our mechanic used it after we had spent three hours searching and we spent less than twenty minutes with it finding two or three small leaks.
Leaks are an absolute pain.
Just my thoughts.
Pres
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Pres is correct and every one of us is going to face the prospect of dealing with leaks.
What we all have to understand is there is no single best way to detect leaks. It would be nice if there was but each leak detection method has limits.
Listen for leaks. If a leak is big enough it will make enough noise so a person can hear it, and follow the noise to the leak.
Use a stethoscope. Cheap stethoscopes are for finding leaks that do not make enough noise to pin down their location, but enough so you can hear them. A stethoscope is great for finding the direction the leak is coming from.
Soapy water. Most leaks do not make noise we can hear so spraying soapy water on connections, fittings, or even devices like Norgren valves helps us see the smaller leaks because of the bubbles. The problem with this method is some leaks take place where we cannot make or see bubbles, like in the bottom “can” of an air bag.
Ultrasonic leak detector as Pres described. With some practice this device can find leaks some other methods cannot locate. It can hear internal leaks in a valve and even a failing relay because it can detect the arcing internal to the relay. But if the leak is in a rubber part like an air bag it will not work.
The final and most difficult, but also the most fool proof is to make a device with a pressure gauge, fill a circuit or device like an air bag with air at a given pressure and look for a pressure drop. Work downstream until you find no more leaks and you have isolated the leaky component. This method is very time consuming and cumbersome but foolproof.
Or as an alternative you can pay someone the equivalent of a college education by turning the coach over to them and asking them to find and fix all leaks. This method is the easiest but you have to choose between having enough money left to buy food or a leak free bus.
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