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Brake chambers leaking
Had new brake chambers put on at Prevost Mia Loma 15 days ago , driving to Knoxville started to lose air out of both prime and secondary air gauges while driving checked it out on road could not hear anything , got to Prevost in Nashville , they said new chambers where leaking they put two new ones on they where leaking toooo, so got two more and tested them on the bench and they where leaking toooo , so if you have to replace brake chambers test them before they put them on with air on the bench, bottom line there may be a problem with the korm berms brake chambers leaking past the park brake when off and passing through the chamber to the ABS valve where it will leak out of and , both gauges will go down when driving. They are drive axle brake chambers that we are talking about same as the ones on the tag axle!!!!!!
Six brake chambers bad , I don’t get it , be careful !!!!!!!
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1 Reply
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Peter and I spoke about this and to help everyone understand the significance of the leak this relates to the DOT per-trip brake check. It may not cause a shut down, but anytime air leaks there is a problem.
This problem will not be seen when the coach is parked because as soon as the parking (emergency) brake is applied air to the brake chambers is shut off. Since no air is going to the chambers there will be no indication of a leak down.
To check for this leak chock the wheels of the coach. Start the engine and bring all air pressures up to their maximum. Turn off the engine, and without applying the service brakes, release the parking brake. What you should see is the air gauges wiggle downwards a slight amount as air pressure is applied to release the brake. Then the gauges will stop moving. Note the pressure. There should be no pressure drop but the typical allowable pressure drop for a commercial vehicle is about 3 PSI per minute. At that leak down rate your air pressure will drop in less than 30 minutes to the point where the parking brake will be re-appliedf.
That is actually a lot of air loss. A leak free brake chamber will stop all air loss. I have released my parking brakes in my garage and for weeks the air pressures in the system have held meaning no pressure loss. I believe Peter expects the same level of performance from new brake chambers.
As a practical matter if the pressure loss when checked according to the above procedure is no greater than 3 PSI you are likely not compromising your safety and the amount of extra work you are subjecting the air compressor to is minimal, but for the coach to be “right” unless you are applying brakes you should not see the brake system gauges cycle very much (assuming a tight aux system).
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