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Why do all 3 Tanks Leak Down at Same Rate?
Believe I have FINALLY pin-pointed my most elusive, albeit slow, air leak to date. This may not be 100%, but hope this helps someone troubleshoot.Over the past 2 years, I have spent countless hours googling, searching this and other groups, yet never found THE ANSWER to what THE CAUSE would be for all 3 air tanks leaking down at the exact same rate. And, neither Better Bubble nor an ultrasonic leak could find it.Realizing the need to study and learn the complete air system, I downloaded from Prevostcar .com the air diagram for my coach, then had it enlarged to 24” x 30” and next colorized it with pencils from amazon after removing fenders and having the bus up on ramps to confirm air line routing. I also re-read the related Prevost Maintenance Manual topics which also identified system components.My search was to find at what point air lines from the primary, secondary, and auxiliary tanks intersect – AND, it is at the secondary air tank! From there it appears the next in-line component is the brake treadle valve.I tested the treadel valve again with both an ultrasonic leak detector and Rectorseal Better Bubble, yet the leak was undetectable so conclude it leaks internally very slowly (as evidenced by my stop watch time test).Currently, after nearly 45 hours, my three air tanks have fallen from 120 PSI to just shy of 90 PSI.***This stop watch time test began immediately after changing all three ride height leveling valves as I found two had slow aux air leaks from their exhaust ports.After all the studying, learning and effort, I believe I will monitor the brake treadle valve and replace it when the leak is detectable – unless someone lets me know that it should be changed now to avoid an on the road issue.***I could not find ANY leaks in any brake relay valve, treadle valve, quick release valve etc., hence my belief it is the treadle valve.Hope someone finds this helpful.P. S. – chassis is 2006 year model and this bus passes the DOT operator’s self brake test AND ALSO Prevost’s tank draining procedure to ensure all tank one-way check valves are operational and that when all tanks are at zero psi at startup, the auxiliary tank does not begin to fill until the primary and secondary tanks have approximately 75 PSI -
3 Replies
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Jeff:
Congratulations on your success after all your time and effort. Enjoy the moment, it won’t last LOL.
Have owned my bus for around 5 years, chasing leaks has been a full time job. I have gotten the leaks down to a point where the air will stay for almost a week. Then after a trip another leak will appear.
Have changed every fitting I have touched to compression fittings, new air bags, new Norgen valves, new bulk head fittings ect
Chuck
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Enjoy the moment… So true! We shall see… I am going to replace the R-14 (despite no bubbling leak) as know that has helped others.
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Mine holds good in summer in the winter it looses air, but over a couple of weeks it may drop 40 or 50 lbs, Driving a 3 gauges hold firm, It use to be driving you could see aux gauge drop slowly then cycle back up, 100 to 120 cycle, but now it stays, So in the winter if it drops slowly OH Well I try not to stress over it. I know that air schematics well. Also the Double shuttle valve under the front if bad will leak all 3 gauges down.
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