Foot valve issue

Been replacing air lines on the 359. Now, when I power up to check leaks, the application pressure for the brakes tracks the pressure for the main air tanks. And I hear air leaking from the foot valve - prob the exhaust. I am guessing that I must have gotten some dirt or crap into the foot valve and it is causing the valve seat to not close. Am I on the right track here? Can I just blow it out or should I be planning to remove the foot valve and do some deeper investigation? I think it is original and is about 40 years old. Should I be planning to R & R it anyway?

John

 

Reman is $50 bucks, so think I will go that way. Thanks for the reply!

One thing I am learning here - old stuff is fragile. Just the activity of removing an air line causes issues. So far I have also replaced a relay valve. Truck is going to be RIGHT when I finish with it.

John

 

Doing them one at a time so I don't think I swapped any, but will re-check. Thanks!

 

Found it! Would you believe the trolley valve was on? Have the steering wheel down to get into the dash and must have pushed it down a bit. Put it back up and all is well.