Troubleshooting Air Parking Brake

[Don Bradner]

Near the end of our recent two-month trip, a couple of hours from home, we came
upon stopped traffic on a moderate downhill. When it was clear that nothing was
moving, I set the brake preparing to turn the engine off. The normal "snap" of
the brake and sudden air release did not occur. Just a minor sound of air
release, and the vehicle wanted to roll when the service brakes were released.

After pushing the button in and pulling out a few times, a normal set took place
and I was able to turn the engine off. Good thing, because we were there about 2
hours - overturned container truck on a narrow two-lane bridge north of Leggett
on US 101.

When I arrived home, the brake set normally on the first try.

Since it is not an ongoing problem, I don't have any idea where to start in
troubleshooting, or if I should just chalk it up to gremlins. I'm not too
worried that the brake, once set, will release, nor am I worried that I might
not notice if it didn't set - the "feel" was clearly wrong before I even tried
releasing the service brake and found that it would roll.

Anybody else ever experience this?

Don Bradner
90 PT40 "Blue Thunder"
Eureka, CA