Air Tank ID

[Adam Hicklin]

Trying to figure out the air system so bare with me and please clarify my lack of understanding.

 I have 2 air tanks as noted by the two needles on the air pressure gauge on the instrument cluster.  I assume one is for brakes and one is for HWH leveling. On mine it appears the green needle is the brake air pressure and the orange is the HWH. Air pressure.  When I turn off the engine, the green needle will leak down some but hold at about 40psi for a long time.  The HWH side (orange needle) leaks down almost immediately however the air bags maintain pressure, again, almost indefinitely.

Is this normal and if I have a leak on the HWH side, where would be the best place to start looking.   

Thanks.

[Mike Shumack]

Air brakes have two separate air systems for safety (a Primary air system - usually Green, and a Secondary system - the red needle). This is in case a air line breaks or a tank or some component fails you still have the "other" system/side to stop the Coach. Then the manufacture ties other non-braking components into one of the systems (like your Leveling, Air Horn, etc.). There is a valve (pressure protection valve) used to shut off the air supply to those non-brake components in the event of a leak so once the air pressure drops to certain point the valve will close and stop the leak from draining out all the air.

it gets a little more confusing when you have air-over-hydraulic brakes. But that's not a "full" air brake system, and even then the hydraulics will have two separate systems.

This picture show a typical coach air brake system. Note that regarding he diagram below, I am in process of creating (for my 2005 Patriot) and have not finished tracing all the air lines, so its incomplete for now.

Regarding your question on the HWH system, there are valve bodies (called "6 pack") that control the air in/out of the air bags for leveling. It is common for these 6-packs to leak air. There is a 6-pack valve bank for each axle (so 3 if you have a Tag axle). You can try to spray some soapy water on the valves to see if any show signs of leaking.

[Fred Brooks]

    Adam, Back in the early 90's when I was the application engineer for a company called "Vogue" we started building our own chassis's. My understanding was the primary brake system is your rear brakes. The rear brakes do 70% of the braking. The red needle (rear) should only move when the brakes are applied. The green needle (front) is your front brakes and all your accessories that are air driven. Your air bags, air horn, leveling system, step well cover, ect. You can see this in action as you drive your coach. When the engine driven compressor shuts off at 120 psi, watch your air gauges or red and green needles on 1 gauge if so configured. The red needle only moves on brake application. The green needle will constantly cycle between 120 psi and 90 psi because you are constantly using air to sustain the air ride height as you travel. The green needle will also move when you apply the brakes. The pressure protection valve that Mike spoke about is your safety device in the event of a major failure in the system. The final safety system is your park brake. If you had an issue while driving and lost ALL your air at once (not ever likely) when the system pressure falls below 40 psi, the park brake starts to apply the rear brakes to stop the coach. Hope this helps, Fred

[Steve Huber Co-Admin]

Adam,
The Chassis Manuals section in Coach Assist (Private BAC Members Only board) has a number of 96-98 Monterey Air system documents. They should be the same or very similar to your coach.
Steve

[Gerald Farris]

Adam,
As Steve said the Monterey diagrams should be helpful in understanding your air system with the exception of the brakes. The late 90s Monterey did not have air brakes (it used air over hydraulic or hydraulic over hydraulic brakes), like your coach. So your brake air supply will be much closer to Mike's diagram and Fred's description.

Gerald

[Stan Simpson]

Someone correct me if I'm wrong, but doesn't the HWH system have its own air tank, and system? It is not included on the red/green gauge readings, as far as I know.

[Steve Huber Co-Admin]

Stan,
If you have air leveling you need to have a tank that supplies the system when you are parked in a camp site, etc. Most have a small tank and electric compressor that keeps it at the needed pressure level. When the engine is running the system switches air supply to the main (usually front) tank.
Steve

[Mike Shumack]

Hi Stan, as the others have said, your Leveling system will use the air from the main tanks (see the diagram below from HWH). Of course these leveling systems vary somewhat from Coach to Coach, but basically they would be similar to the diagram.

The air for the air leveling comes from the main (front and rear) air tanks and is fed through the HWH "6 pack" valves, and then to the air bags. When the Coach is in auto-level mode, the air bags are "isolated" from the main air tanks, so the tanks can lose all their air pressure but the air bags will stay inflated. And on most systems, if the air bags do lose/leak air, and the tanks are empty, an electric air compressor will come on and add air to the bags (note that the electric air compressor does not fill the air tanks).

Some Coaches have an extra set of small air tanks called "ping tanks" but these are just for airbags and don't supply air for other things.

[Lee Welbanks]

Adam, Does your air leak off with the coach in the travel mode just parked? Does it leak off when parked and in level mode? There are about a thousand different places and fittings that could be leaking. The pressure switches and solenoids that HWH used are a good place to start and any tube fitting in the system. A spray bottle with dish soap and water to spray every tube fitting  you can find under the coach is how you find the leaks. Don't know if they used push to connect tube fitting with you coach year, but they tend to leak, I've replaced a lot of them with Parker old school DOT air brake compression fittings, they don't leak.
Make sure you block up the coach so there is no way it can come down on you while under it. With my 06 Patriot Thunder I can just slide under the front and rear if it is all the way down.

[Adam Hicklin]

So this is what happens.  I pull in to a space. Level the coach with he engine on.  Get leveled up.  Turn off engine.  I pulled in to a space about 3 hours ago.  Both red (orange) and green needles are at 60psi right now.  Over the next few hours, the red needle will leak down to zero.  The green will stay 40-60psi.  Airbags stay inflated.  They do not leak down.  Now say tomorrow, if I need to make a leveling adjustment (inflate/raise) I'll hit the button, the new (thanks to Gerald for the instruction installing) auxiliary compressor will come on and the red needle will begin to raise from zero, to about 30psi, when it will start adjusting the airbags.  Green needle never moves.  So that's kind of opposite of what Fred described. 

[Steve Huber Co-Admin]

Adam,
Sure sounds like your gauge indicator is reversed. I checked the manual for a 2002 Marquis, one of the few that details which needle monitors which tank, and it shows that the red needle shows primary tank pressure and green shows secondary. Easy way to check is to start engine and then pump brake pedal repeatedly. Your green needle should begin dropping after a bit. Some Beaver coaches ran air lines to the gauge. If this is the case with yours, it could simply be that someone inadvertently reversed the lines at the gauge after doing some work on the dash.
Also sounds like Mike is correct in that you don't have a "ping tank" but rather the electric compressor is hooked to your secondary tank. You can physically ID secondary tank by tracing line from electric compressor.
Steve

[Fred Brooks]

    Adam,
I think Steve may be on to it. From your conversation, the gauge needles are transposed. To prove that, next time you drive the coach, observe which needle cycles between 90 psi and 120 psi. Which ever needle that is, is your secondary tank. That tank is your air ride and front brakes and it sounds like your HWH supply tank also when parked. Fred