Brake pedal valve

[Chamberpains]

Aftermarket makes me cringe. Bendix makes good reman stuff and hell new ain't that expensive. Almost any price is better than having to contort yourself up to get at that SOB more than once.

Well at least you say your working with a KW W900. They aren't the worst treadle valves to get to. Sounds like you got a faulty one. But also check that you have it plumbed correctly. Its a spider web of air lines but they all need to go exactly where they need to go or the valve will not send air where it needs to go. Sometimes causing your exact problem.