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Losing brake air pressure when parked
Our coach used to keep up brake air pressure for weeks. This changed during our last trip. Now, both primary and secondary gauges are at zero after two days parking. I see no cycling of air pressure when driving on highways without brake application.
Before I get the coach up on the ramps I’d appreciate some input on where to look other than the primary and secondary drain valves. Both tanks lose pressure at the same time. Does that mean the protection valves are inop?
Thanks, Gerald
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6 Replies
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I would put money on the “Parking valve”. It is one of the few places where both primary and secondery air are tied together. I had the same problem a few years ago and Peter told me to change the parking valve and that solved my problem.
If I understand the air system, there are very few places where an air leak can cause both primary and secondery air to drop at the same time.
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You may want to check the R14 valve as well.
Fred
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https://prevostcommunity.com/forum/threaddetails.asp?Category=Pneumatic&ThreadID=6143
Jeff and Lindsay
91 Marathon XL -
Gerald,
When you are parked there is no air at your brake chambers. You can limit your efforts pretty much to the relay valves as has been stated above or the foot treadle.
Some vintage of coaches had a history of leaking at the small ail line going into the rear of the pressure gauges on the dash, but that would be down the list because you said both go down. Start with the relay valves as most probable. BTW, they are cheap and easy to replace once you get at them.
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Very helpful – thank you all. I did not see lonestar’s thread when I searched the forum for brake pressure issues. This should get me started.
Gerald
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I had the same issue, however, it would deplete in 5 hours … took to Prevost Jacksonville and the Bendix valve on driver side between tag and drive was leaking badly,this is the valve that controls park break too.Replaced and pressure remains same for weeks!
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