The brakes on these trucks are wedge brakes. One of the guys at the local Truck Pro commented that wedge brakes are obsolete now with other self-adjusting brake systems. He asked if the truck was really old and was surprised when I told him mine was a 93 model. If you are completely new to air brake systems like I was, I suggest you do some reading about how the brake chambers work, it will help quite a bit when you start troubleshooting them.
Wait, wasn't replacing this a bit on the DANGEROUS side?
Here is a link to a Haldex catalog that lists wedge brake chambers:
http://www.haldex.com/Documents/hbsn...g%202-2012.pdf
The rear chambers are a trade size 9/12, which means the inside (service) diaphragm is a trade size 9, and the outside (parking) diaphragm is a trade size 12. On these the parking brake portion is removable, although I would probably not recommend it. Due to safety concerns, the parking brake section on most new style chambers is crimped closed so you can't open it. There is info online about the dangers of the parking brake springs if you are curious. The service brake side of the chambers can be accessed, just remember to cage the brakes before you open it.
On my truck, I had and air leak in the rear when applying the service brakes (brake pedal). I was able to trace the air to the vent line that runs up to the frame rail and vents there. This pointed to a leak in the service brake diaphragm which was allowing air into the vent line. You can pick up a size 9 seal for under $10. The only caveat is that with the factory seal, the plunger piece is glued to the seal. Aftermarket seals are not made this way. So, for the cost I decided to just attach the plunger piece back to the new seal. I removed the old seal, peeled it off the plunger, scraped the plunger, wire brushed it, cleaned with alcohol, and applied contact cement. So far so good on the repair. I think there is probably a better adhesive option, but not that I could get locally to fix mine in a hurry.
In this pic, you can see one of the factory seals on the left with the plunger attached. The plastic bushing shown has been removed from the one on the right while I was repairing it. On the right is the aftermarket seal with the plunger piece glued back to it. The factory seal was shaped so that the center was raised, the aftermarket one is not, but works just fine as far as I can tell.
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Was'nt replacing these a bit dangerous?Originally Posted by Oxyacetylene
James
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