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brake treadle - Printable Version

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brake treadle - gasparillaglass - 04-25-2008 23:39

When I push in on the brake treadle without motor running the
presure
drops steady and i would say rather fast .
When I run the motor it builds up
I have to put her in a high idle to get it up to release the spring
brakes about 110
from what I remember before I had the oil pan gasket replaced it
didnt do this
anyway I guess the big question is where is the air going??
anyone have any adea??
thanks to all
heres another one he he
also after the pan gasket was changed .
When I load up my air spring everything is good without dumping the
air bags and just putting down the leveling jacks I loose the back
right air in the air bags just on the rear right side not in the tag

Jamie Brandt
SW FL.
1990 wb40

brake treadle - Pete Masterson - 04-27-2008 06:48

You need to fully understand your air brake system. It sounds like you have a leak. It could be most anywhere in an air line or at one of the brake drums. It probably doesn't have anything to do with the oil pan gasket replacement (although a particularly sloppy mechanic might have damaged something).
Here is a relevant section from the CA Commercial Driver's handbook:
You can read the complete air brake section at this URL:
<http://test-www.dmv.ca.gov/pubs/cdl_htm/sec5_a.htm>

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. [/list]

    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. [/list]

      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.


      *Check air compressor governor cut-out pressure. Pumping should start at about 100 p.s.i. and stop at about 125 p.s.i. (130 p.s.i. maximum). Run the engine at a fast idle. The air governor should cut-out the air compressor at about the manufacturer's specified pressure. The air pressure shown by your gauge(s) will stop rising. For testing purposes, identify when the compressor cuts out.


      *Check air compressor governor cut-in pressure. Start with the air pressure above the governor cut-in level (no lower than 85 p.s.i.). With the engine idling, slowly pump the brake pedal to reduce the air tank pressure. Watch the air gauge between pumps to identify when the compressor cuts in (needle starts to rise). This should be at about the manufacturer's specified cut-in pressure. If the air governor does not work as described, it may not keep enough air pressure for safe driving. For testing purposes, identify when the compressor cuts in.


      NOTE: To perform this test correctly, the compressor cannot already be pumping air. If it is, allow the governor to cut-out before performing this test.


      Test parking brake. Fasten your seat belt. Set the parking brake and try to move the vehicle or allow the vehicle to move forward slowly and apply the brake. The parking brake should not allow any movement.

      Pete Masterson
      '95 Blue Bird Wanderlodge WBDA 42
      El Sobrante CA
      "aeonix1@mac.com"
      On Apr 26, 2008, at 4:39 AM, gasparillaglass wrote:

      When I push in on the  brake treadle without motor running the 
      presure
      drops steady and i would say rather fast .
      When I run the motor it builds up 
      I have to put her in a high idle to get it up to release the spring 
      brakes about 110
      from what I remember before I had the oil pan gasket replaced it 
      didnt do this 
      anyway I guess the big question is where is the air going??
      anyone have any adea??
      thanks to all
      heres another one he he 
      also after the pan gasket was changed .
      When I load up my air spring everything is good without dumping the 
      air bags and just putting down the leveling jacks I loose the back 
      right air in the air bags just on the rear right side not in the tag 
      Jamie Brandt
      SW FL.
      1990 wb40Â