[Reese]

Both dropping simultaneously suggests possibly a parking brake relay valve might be leaking or maybe a leaking brake chamber.

Just to see if that is a reasonable supposition, air up the coach with the parking brake engaged and then turn it off. When that is the situation air is locked in the tanks by the relay valves. If you do not see a pressure drop, block the wheels and relase the parking brake with the engine off. If you see a pressure drop where there was previously none then the brake chamber diaphragm might be the issue.

Neither problem repairs itself and usually they tend to get worse, sometimes very fast so it is important to isolate and fix the problem.

[David]

Sounds to me to be a problem with either:

a) the unloader valves in the engine driven air compressor, or

b) air compressor governor, or

c) air dryer

Normal engine driven air compressor operating range is 90 to 120 psi, not 100 to 110.

[Archived]

Hi Jon,

With the coach off and after releasing the parking brake there was a audible hiss in between the drive / tag wheels…the hiss was the same on the left and right so I am assuming it is near the center of the coach.

I have a friend coming by and bringing jacks so i can safely get under the coach. I should be able to isolate the leak as loud as it is when I can get underneath..any thoughts on what it may be?

David Thomas

1998 Featherlight XL

[Towson]

110 seems to be a little light on the compressor governor setting, should be 120/125.

[Roy]

My guess is a relay valve, top center between the axles bolted to the underside of the floor.

If you can support the chassis with it raised all the way up so you are safe, you can slide into the area between the axles, sit up and reach the valve to remove and replace if that is it.

[George]

Hello,

An update to my air pressure loss..it turns out that is was the tag axle spring brake supply line. It was loose at the “T” that sends air to the right and left of the tag. Big shout out to my friend Billy of Piedmont Ok for bringing his jack stands for safety and getting under the bus and finding the leak. I did a lot as I handed him the crescent wrench he needed to tighten the hose. All is well now.

David Thomas

1998 Featherlight XL

[Gerald]

I experienced a problem very similar to this, today. Took the coach for a short drive, took a walk, and when I returned, the low air alarm went off at start up. It aired up to 125 and stayed 95-125psi as I carefully drove back while watching both gauges drop, slowly. When I parked and put on the parking brake, I could hear an audible hiss near the right drive wheel. I did not listen to the left side. I don’t have a bottle jack or 20T jack stands, so I assume it’s best to keep it parked and get someone to come out for the repair rather than try to drive it somewhere?

[Archived]

When the parking brake is on all brake system air pressure is between the primary and secondary air tanks and the brake relay valves.

If a noise of escaping air is heard when the parking brake is on it could be a relay valve or something associated with the tank and line from the tank to the relay valve.