04-08-2017, 08:43 AM
To answer the last two questions asked;
I doubt it's the compressor for the following reason; there is a separate check valve at the inlet of each brake tank. In order for a compressor leak to be the problem both of those check valves would have to be leaking and at the same rate since the needles are dropping in tandem. My 120V compressor feeds into the inlet of the main air dyer.
The gauge with the twin needles for the brakes could be leaking internally. I did have a small leak in one of the two fittings on the gauge and they now check leak free. The reason I doubt the leak is internal is that I would not expect a single internal leak to effect both needles. If there were to be two leaks internally the odds that they were exactly the same size strikes me as nearly nonexistent. However, I am assuming that the internals for the two needles are independent of each other. I may lack the imagination as to a configuration where they aren't independent.
There is a place where the two brake circuits come together, the parking brake knob device. OK, it has some other fancy name that escapes me at the moment. While only the rear brakes have spring-brake actuators on the (I believe), both brake tanks supply pressure to the knob device. I've examined a cut-away of that device and failed to understand exactly how the two supplies are used. Today I will leak check that. At 50-60 psi the leak down is only 5 psi per day so the leaks I'm trying to find are tiny, but to salve my obsession, I hope are detectable. I will boost the pressure to the cutoff of the 120V pump.
I appreciate the suggestions, as I consider them they deepen my thoughts and understanding even if I conclude they aren't the solution in this case. Any time I can better understand this complex air system I know it will be useful in the future. For those of us to whom complexity is scary, your gifts of suggestions are invaluable.
I doubt it's the compressor for the following reason; there is a separate check valve at the inlet of each brake tank. In order for a compressor leak to be the problem both of those check valves would have to be leaking and at the same rate since the needles are dropping in tandem. My 120V compressor feeds into the inlet of the main air dyer.
The gauge with the twin needles for the brakes could be leaking internally. I did have a small leak in one of the two fittings on the gauge and they now check leak free. The reason I doubt the leak is internal is that I would not expect a single internal leak to effect both needles. If there were to be two leaks internally the odds that they were exactly the same size strikes me as nearly nonexistent. However, I am assuming that the internals for the two needles are independent of each other. I may lack the imagination as to a configuration where they aren't independent.
There is a place where the two brake circuits come together, the parking brake knob device. OK, it has some other fancy name that escapes me at the moment. While only the rear brakes have spring-brake actuators on the (I believe), both brake tanks supply pressure to the knob device. I've examined a cut-away of that device and failed to understand exactly how the two supplies are used. Today I will leak check that. At 50-60 psi the leak down is only 5 psi per day so the leaks I'm trying to find are tiny, but to salve my obsession, I hope are detectable. I will boost the pressure to the cutoff of the 120V pump.
I appreciate the suggestions, as I consider them they deepen my thoughts and understanding even if I conclude they aren't the solution in this case. Any time I can better understand this complex air system I know it will be useful in the future. For those of us to whom complexity is scary, your gifts of suggestions are invaluable.
Jon Kabbe
1993 coach 337 with Civic towed