glitchwrks Posted June 12, 2018 Share Posted June 12, 2018 As noted in the Midliner project thread I now seem to have an air leak at the exhaust port of my foot valve. I did a hard stop before coming up the driveway and suddenly dropped to 30 PSI on both circuits and couldn't build past that at idle. I was able to rev it up to build enough to release the spring brakes and get up the driveway. I pulled the service side lines off the rear brake cans and got no backflow out of them. With the engine stopped, park brake set, and service brakes not applied, it was still leaking from the foot valve exhaust port. Reconnected the service chambers, chocked the wheels, released the spring brakes, and gave it a few hard, full applications...magically, the leak was way, way less but still present. I'd read a bunch of other BMT posts before making this one, and seen that a lot of people hose them down with WD-40 or some other very thin lubricant first, before replacing. I figure it's a piece of crud or some internal rusting caused by the previous owner's lack of maintenance on the air system (e.g. not blowing down tanks). It's a pretty new WABCO foot valve (looks like it was put in probably 2015). I'm planning a three-hour trip down to Winston-Salem and back later this week, is this something I should just bite the bullet on and have replaced now, or see if I can give it a workout and free it up? Quote Link to comment https://www.bigmacktrucks.com/topic/53554-air-leak-at-foot-valve-exhaust/ Share on other sites More sharing options...
j hancock Posted June 12, 2018 Share Posted June 12, 2018 With your traveling, a new one sounds good. Doing a little driving in the yard may clean it out. I have taken them apart and inspected the seals and cleaned the bore. Gave the seals a very slight amount of petroleum jelly and it hasn't caused any other issue in 10 years. This was on a truck were a direct replacement was not readily available. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/53554-air-leak-at-foot-valve-exhaust/#findComment-400437 Share on other sites More sharing options...
glitchwrks Posted June 12, 2018 Author Share Posted June 12, 2018 Shop took a look at it today, mechanic said it was almost certainly crud or moisture from poor maintenance of the air system by the previous owner. They sprayed some air line cleanout/dryout chemical in there and worked it back and forth a few times, more or less no leak after that. Quote Link to comment https://www.bigmacktrucks.com/topic/53554-air-leak-at-foot-valve-exhaust/#findComment-400449 Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.