Community Forums

tom chelbana · 08-29-2016, 08:34 PM

Once a week someone is posting on issue with air leaks and numerous times it is the either the air compressor governor or air drier. The September issue of FMCA magazine has a detailed article on checking those two items plus your air brakes. I will be photo copying this article and putting it in our briefcase of brochures and information items to carry in our Newmar.

Adam Hunter · 08-30-2016, 06:51 AM

The following is a good reference. It is the procedure that will get you through a air brake "Z" endorsement in the province of Ontario. It only takes a few minutes to do and I include it as part of my walk-around. I leave step #8 for my mechanic, however you are required to demonstrate this step when you get tested. The following is a guide that may or may not apply to your unit.

1. *SECURE THE VEHICLE - Set the park brake - Chock the wheels.

2. TEST THE LOW AIR WARNING DEVICE
Engine off, key on.
Air pressure is over 90 PSI
Pump the service brakes
Warning Device on at 65 PSI is good
Device on below 55 PSI vehicle is defective.

3. TEST AIR PRESSURE BUILD UP TIME.
Start Engine and run between 600-900 RPM
Reduce air pressure to 90 PSI
Time from 90 PSI to 120 PSI
Less than 30 seconds is good
More than 30 seconds vehicle is defective

4. CONFIRM AIR COMPRESSOR GOVERNOR SETTINGS
Build air pressure to maximum and note cut-out pressure
Cut-out must be between 120 PSI and 135 PSI
120 PSI is good
More than 135 PSI vehicle is defective.

Pump down pressure 20 to 30 PSI - Until compressor cuts-in
Cut-in should be @ 100 PSI
100 PSI is good
Defective if less than 90 PSI

5. TEST AIR LOSS RATE
Release spring brake
Apply service brake and shut engine off - key on.
Time for 1 minute.
Note air loss
1 or 2 PSI is good
Defective if more than 3 PSI
Spring Brake ON.

**REMOVE FRONT WHEEL CHOCK**

6. TEST SPRING BRAKE
Apply spring brake
Start engine, select drive.
See if spring brake holds
Spring brake holds - vehicle good
Defective if vehicle moves

7. DRAIN AIR TANKS
Shut off engine, key on. Proceed to front of bus.
Drain FRONT WET (supply) tank for 5-10 seconds
Go back to gauges, see if no change to PSI. = Wet tank gauge.
Drain 2nd valve for 5-10 seconds. FRONT DRY. - Look for oil, sludge, water.
Drain 3rd valve for 5-10 seconds. REAR DRY. - Look for oil, sludge, water.
If valves work - vehicle good
Vehicle defective if valves faulty

8. INSPECT BRAKE ADJUSTMENT
Vehicle Chocked, Spring brake off, engine off
Air 100 PSI or more
Determine size of brake chamber by measuring diameter of clamp ring.
(Insert Brake Adjustment and size for your coach here)
Mark pushrod and apply service brake with device. Measure pushrod stroke.
(Air 90-100 PSI)
Vehicle good if measurement equal to or less than adjustment limit.
Vehicle defective if stroke greater than adjustment limit.

9. DEMONSTRATE VEHCLE KNOWLEDGE.
IF ANY DEFECT IS FOUND DURING THE BRAKE COMPONENT INSPECTIONS OR TESTS THE DEFECT WILL BE REPORTED, *THE VEHICLE IS DEFECTIVE AND IT WILL NOT BE OPERATED UNTIL REPAIRS ARE COMPLETED BY A LICENSED TECHNICIAN*.

tom chelbana · 08-30-2016, 03:37 PM

Adam With your information and the FMCA article Newmar owners are going to have the information about their complete air systems. Will be photo copying this information to add to the FMCA article.

Adam Hunter · 08-30-2016, 04:14 PM

That's fine Tom,

I am glad to share this info. Here in Ontario air tests conforming to the above guidelines are acceptable for compliance standards.

For other forum members it should be noted that it would be safe to consult with specific manufacturers specifications as some differences for tolerances may exist from chassis to chassis.

For example; (Air loss rate can be more if you have combination units such as multiple trailers, etc.)

Adam