We've been parked on a level site for nearly a week. For the first time in 3 months on the road I noticed the top air guage has dropped. Prior to this time both gauges would slowly drop over a week or so from 110-115 to 90-100 or so. We moved the coach slightly on our site yesterday and I noted a shutdown pressure of 110-115 on both tanks. This morning the top guage shows 70 and the bottom guage is still 110. I'll watch today to see if the top guage falls further.
We'll be covering roughly 1200 miles over the next 2 weeks and generally located away from major Service centers. How significant to travel safety is this issue? Both tanks quickly came up to travel height when we moved yesterday.
Thanks
Not at all.
You could have a check valve leaking on the line that feeds the air tank or a slight hose leak at a fitting.
Mike
Turn everything off and listen around the park brake valve for a faint hiss. The acceptable leak down is well above your values.
Over 150K miles my air system has never been that tight. Go!!
Since posting the top guage has mirrored the bottom and both have resumed their "normal" and acceptable leakdown. What would cause this to happen sporadically? Not concerned at this point.
Intermittent malfunction of gauge (if mechanical) or of sender/wiring/grounds (if electronic).
I had to replace one of my gauges when I experienced the same condition. if it does it again switch the air lines on the top with bottom gauge, and see what it reads,
Randy,
You have a good, leak tight system. Don't be concerned. Just stay aware of trends.
You need to realize that when you move a coach from one position to another, no matter how small or how undramatic the changes may seem to be in terms of leveling system actions, literally dozens of valve to seating surface conditions were changed during the short moving process. Compressor to D2 governor to check valves on tanks to six-packs to leveling valves — a lot of seating surfaces have been exercised, even in a short repositioning event. If any one of those valve to valve-seat changes ended up not quite perfectly seated, for instance due to a temperature or a contaminant particle influence, there may well be nothing unusual about your occurrence. There is also a very high probability that the anomaly will clear during the next exercise of the coach.
You need to sit up and take notice when you notice major, repeatable degradation step changes, toward FT and then DOT air leak specifications. The air leak specs are nicely summarized in BeamAlarm:
D.O.T. Standard Allowable Leakdown (http://beamalarm.com/Documents/D.O.T._standard_allowable_leakdown.html)
Easy summary:
FT = 6 psig drop/hour = 60 psig drop/overnight
DOT = 4 psig drop/2 minutes
HTH,
Neal