Quote:
Originally Posted by MoHoGo
DeeGee, the jack stand comment puzzles me too. Maybe just to make legal happy.
Eddie, the other point is that Spartan wants you to lower the air pressure to below ~70 and then air up before beginning the tests. I am wondering if there is a valve sequence that needs to initialize first.
Anyone have a link to Mark Q's article please post.
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Hello, I don’t have a link but this is the article by Mark Quasius:
Air system checks
The gauges are probably labeled front and rear but that's not the air bags (suspension). Those are the front brakes (secondary system) and rear brakes (primary system).
If your examiner asks about the correct draining procedure you might want to be familiar with the following, which will be part of an upcoming article in Family Motor Coaching magazine:
Most coaches are equipped with lanyards to operate the manual air tank drain valves. Generally these are located inside a wheel well but exceptions exist so check your manual for the exact location of the lanyards or valves on your particular coach. Modern coaches will be equipped with an air dryer that provides clean, dry air to the system so you may feel the need for manually draining the air tanks is an exercise in futility but that is not the case. If the air tanks are drained in the correct procedure it serves as a diagnostic tool to check the integrity of your air system. First of all, if your air dryer is functioning correctly you will see little or no moisture being ejected from the air tanks when you pull the lanyard. Secondly, by using the following procedure you will be able to verify that your various check valves are operating correctly:
1)*Make sure both air gauges are reading 70 PSI or less. If the gauges read higher bleed the system down by pumping the brake pedal until the gauges read 70 PSI or less.
2)*Start the engine and run at high idle (1200 RPM or higher) until air dryer purges in the back of the coach.
3)*Never reach your arm into a wheel well or crawl beneath the coach when you drain the air tanks. If you can’t safely reach the lanyards with your*awning*hook use some way, such as jack stands, to support the vehicle.
4)*Turn the key to the “off” to stop the engine. Then turn the key back to the “on” position so that the gauges will function. Do not start the engine.
5)*Locate your lanyard or petcock locations. There should be three of them, one to each tank although some tanks are split into two separate compartments so there may be two drain valves on one tank.
6)*Drain the air completely from the wet tank. This should be identified by a clear or gray lanyard cable.
7)*Go into the unit and check the gauges. They should not read zero. This will ensure that the check valve between the primary and wet tank is functioning properly.
8)*Next drain the primary tank completely. This should be identified by a green lanyard cable.
9)*Check the air pressure gauges once again. The rear gauge (primary system) should be reading zero and the front gauge (secondary system) should not be reading zero. This will ensure that the check valve between the primary and secondary tank is functioning properly.
10)*If either of these valves is not functioning as they should, take the coach to a service center to have these valves cleaned or replaced.
11)*Now drain the secondary tank completely. This should be identified by a red lanyard cable.
12)*Check the gauges again. Both gauges should now read zero.
13)*If significant moisture was found when draining the tanks it’s time to have the air dryer serviced.
14)*Make sure that all of the petcocks or drain valves are closed and restart the engine. Run at a fast idle until the air dryer purges. The system should now be ready for operation and both gauges should read somewhere around 110 PSI.
Your air system is equipped with a low air pressure alarm system set to actuate at a minimum of 60 PSI, which is when the spring brakes will apply. Once the air pressure drops to 20 PSI the yellow push-pull valve will also pop out. You can test these systems in the following manner:
1)*Turn the ignition key to the “on” position to enable the air pressure gauges and low air alarm system. Do not start the engine.
2)*Place your foot on the service brake and release the parking brake.
3)*Pump the brake pedal and monitor the air pressure gauges. Once the air pressure drops to no lower than 60 PSI the low air pressure alarm should sound and a red light will illuminate on the dash or in the pressure gauge itself.
4)*Continue pumping the brake pedal. Once the pressure drops to 20 PSI the yellow parking brake knob should pop out.
5)*If the alarm does not sound at a minimum of 60 PSI or the spring brakes do not actuate your brake system will need to be serviced.
Pre-Trip Inspection
1)*Manually drain the air tanks.
2)*Run the engine at fast idle. The air pressure should go from 50 PSI to 90 PSI in less than 3 minutes.
3)*The air governor should unload the compressor at a minimum of 115 PSI and a maximum of 135 PSI.
4)*Fan the brake pedal to drop the air pressure to 80 PSI. If the governor is functioning correctly the pressure should begin to rise.
5)*Continue fanning the brake pedal. The low air pressure alarm should sound at approximately 60 PSI.
6)*Build up a full head of air pressure and switch off the engine.
7)*Release the spring (parking) brake.
8)*Apply full brake pedal pressure and hold.
9)*Hold this pedal pressure for at least 2 minutes. The air pressure should drop no more than 3 PSI per minute. If there is excessive pressure loss you have a leaky fitting or component in your brake system. Note that this assumes that your air-ride suspension is fully inflated and no longer using chassis air to inflate the air bags.
Mark Quasius
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