ABS LEAK

What are you pinching the lines off with? Vice grips usually won't get them 100% closed.

If the brake chamber park diaphragm had a hole in it, it would not exhaust out into the service side, it'll blow out the back of the chamber, service side will blow out around the pushrod. The only way they're going to allow backfeeding is if the seals on the interlink pushrod in the middle section have failed.

 

Your Quick release valve should have an air line going to your service valve. Pull that air line off with brakes released, if there is air there, your QR valve is bad, which would cause your abs valve to leak out the exhaust

 

Change lines also

 

Quick release valve is normally under the 5th wheel. It will probably have a red supply, a blue service signal, and your air lines to the brake chambers supply