Air tank pressures unbalanced and Parking break question

In that case, I would set the tractor brakes and see if they would hold it when putting it in gear and also look at the slack adjusters and steer axle slacks while someone applied the pedal. As long as the tanks could build to 120 psi would be my concern, any rapid loss would be cause for alarm. All in all you made a smart decision and it’s ultimately on you if something bad happens on the road.

 

Uneven air pressure is not uncommon and I have never seen a regulation on that. I cannot say you are wrong about not driving a vehicle that the park knob does not pop out within regulations. You are the pilot in command of your ship and responsible for the safety of all.
Personally if it passed all the other tests I would not be to concerned. I have never seen that written up on a DOT inspection. The spring parking brakes normally start to apply around 60 PSI and I would expect you to be on the side of the road locked down before 30 PSI anyway.
Straight trucks with air brakes have a little different air system than combination vehicles. At low pressures they can start sucking up some air using the spring brakes for stopping in conjunction with foot pedal operation if fanning.

 

On all the trucks I've ever seen, both tanks will fill fairly even, there may be noticeable pressure difference while filling but they will both top out at 120 psi. When you fan the brakes, it is quite normal for the tanks to drain uneven. The service brakes pull off of one tank, that tank will drain faster than the other.

Doesn't sound like there was anything wrong with the truck in question. Was there a mechanic or more experienced driver available to ask about this before you refused to drive? You won't make many friends in management refusing to drive a perfectly safe truck.

Even if the button doesn't pop at all, it's technically a infraction upon inspection, but isn't all that dangerous if you know how to drive. The fact is, if your psi gets to 20-30, your brakes will come on anyway on modern trucks with spring brakes. I can't think of too many situations where you want that button to pop out, but if you find yourself in that situation where you need the button to pop and it doesn't, you can always reach up there and pull it out yourself. Personally, I'd much rather the button come out when I wanted it to, rather than pop out on it's own. You're going to go to full lockup pretty fast if that button comes out while moving.

 

On further thought, I recall a test I used to make on older trucks.

I would apply the brakes with the service (Foot) and wait a minute. There should be a initial drop in both primary and secondary and pause in the drop then a VERY slow trickle off in pressure. If the engine was on the compressor would be able to keep up if not refill the tanks against that little bit of leaking. Say 2 pounds over so much time.

Keep in mind this was a VERY long time ago for me and I am reaching into the cobwebs of my memory. It's beginning to be easier to catalog what I have forgotten versus what I still know.

 

No infraction as there is no federal requirement for the yellow park brake button to pop out. It should pop somewhere in the 20-30 psi range, it’s just not federally required to.

 

Highway patrol put me OOS for valves not popping out. Mechanics had to come out and change the assembly in the dash.

This was long before CSA rolled out though.

The truck I'm in now won't pop out. I'm not getting in to that story. But the alarms work so that's all I'm concerned about. Already had the compressor go out 2 miles from barn. Alarms came on. Sat and waited for wrecker to tow me home. FRiday night and 2 extra hours to get home.

Sometimes my truck builds up evenly. Most times it don't. But it bleeds off pretty evenly. Unless i get an air leak. Which happened once.

 

Back in the old days some state inspectors would OOS a vehicle for the yellow park brake button not popping. The CVSA issued a bulletin in 1997 to stop the practice because there was no federal requirement. The only reference to the yellow button popping was in the CDL manual which they and Bendix air brakes stated was inconsistent with the Regs. The bulletin number was 97-1. It has since been rescinded and replaced administratively.

 

So the cop was in the wrong. This happened sometime around 07 or 08.