Well I found the leak. Now I need to work out how to safely fix it. Thanks for all the advice and patience. I’m learning a lot here. First rig with air brakes.
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@G744 and
@Floridianson are dead on the money! You need more information before you jump in and "just fix" the air chambers on any air brake system.
First of all :
Think Before You Die. There is a spring behind the outward facing "cap" on the air chamber. That chunk of aluminum will knock you out cold if it doesn't kill you first.
No Bull. You don't have the required caging bolt in it's holder in the picture that you uploaded. You really need that bolt before you do anything.
Technically you can remove and replace the complete "can" without the caging bolt, but this is a learning session. So please get yourself a caging bolt and know how to use it.
I added a few pictures so you can have a good understanding about what the caging bolt looks like and how it is used. Even some written TM instructions...
Don't hesitate to
ASK QUESTIONS before you turn wrenches. Nobody here will give you grief or cajole you about this particular piece of truck repair. It's no joke for sure!
EDIT
I couldn't help myself... Added one more picture below. That big spring on the right is what is hiding behind the "cap" that is NOT bubbling in your picture. The caging bolt is inserted (from left to right in this picture) to capture and cage (secure) that monster spring.