Air pressure SP36

[Pete Masterson]

No, it is not normal. You have an air leak. Below is an excerpt of
the Air Brake Check from the California Commercial License DMV
booklet. While this test isn't required for RVs, it is a good test of
what's considered safe in an air brake system. Note that the fully
charged system should not lose more than 3 psi in one minute with the
brakes held on. It's time for some serious examination of your air
system.



In-Cab Air Brake Check

NOTE: All items marked with an asterisk (*) are critical parts of the
in-cab air brake test and must be demonstrated during DMV testing.
They may be performed in any order. If these items are not performed
correctly, it is considered an automatic failure of the pre-trip test.

Test air leakage rate. (* second test only)

* With a fully-charged air system (typically 125 p.s.i.), turn off
the engine, release the service brake (brakes off), and let the
system settle (air gauge needle stops moving). Time the air pressure
drop. The loss rate should not be greater than:
— 2 p.s.i. or less in one minute for single vehicles.
— 3 p.s.i. or less in one minute for a combination of two vehicles.
— 5 p.s.i. or less in one minute for a combination of three or more
vehicles.
If the loss is too much, check for air leaks and fix.

* With roughly a fully charged air system (typically 100-125 p.s.i.),
turn off the engine. Release all brakes and allow the system to
settle (air gauge needle stops moving). Then apply full steady
pressure to the brake pedal (brake on) and hold. After the system
settles again, the air loss should not be more than:
— 3 p.s.i. or less in one minute for single vehicles.
— 4 p.s.i. or less in one minute for a combination of two vehicles.
— 6 p.s.i. or less in one minute for a combination of three or more
vehicles.
If the air loss is too much, check for air leaks and fix. For testing
purposes, identify if the air loss rate is too much.



Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42

El Sobrante CA
aeonix1@...



On Aug 10, 2007, at 8:43 AM, williamcharrison wrote:

> I was waiting in line on a slight grade at a Flying J with my
> foot on the brake (probably 1 minute) and I noticed quite a drop
> in air pressure and then my steps came out. I set the parking
> brake until pressure came back up and the steps retracted.
> Is this normal, and if not, what corrective action need I take?



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