Hello! Need help please. The yellow knob is not popping out.

No..that was jus some comments I have found online. When I look for answers I look…for people who had similar problems in the past, and see what answers they may have received back.

 

This morning I had to move one of the new WS that was delivered last night. I hooked the trailer air lines to it, ran it up to full pressure, pushed in both valves, shut it down, drain the air and guess what?

The red one popped, the yellow one didn't.

This truck has 634 miles on the clock.

 

Does the red knob (trailer parking break) pop out?

 

Buy the entire dash valve. You said you rebuilt it twice, it's time for a new one.

 

Oh, that was a different truck, and it was leaking air one time, and the yellow valve would get very sticky, hard to open close, I think next time. It was different issues with it.

 

The tractor protection valve is nothing more than a valve that when air is applied from the red button, it opens the valve and allows service air to the trailer. If you disconnect the red line from the trailer while the red button is pushed in, the red button should pop out, but I’ve never been in a truck where the yellow button will also pop out. In the most basic terms, yellow is to set the tractor brakes, and red is for trailer air supply (which when pulled out also applies the trailer brakes).
Also, you have systems that have a red and yellow button, but there are some that also has a blue button.

 

So you've never driven a truck that's never had a properly functioning valve.

Even the 88 kw I drove popped both valves.

 

Yes, the tractor protection valve have nothing to do with the yellow knob, so it’s most likely the valve. It gets clogged with oil/water from compressor, when the filter , the air disecant needs to be replaced. Not a lot of service on that one, everybody skip in that filter, the worst was the Columbia with auto transmission, and it was operated with air that would clogged valves, and the truck, will not shift, or allow to move from parking to drive. Detroit have dirty compressors,

yes

 

They both will pop out if you have a loss of air in the whole system, but if you just have a loss on the trailer supply (as can be simulated by disconnecting the red trailer line while the red button is in) only the red button will pop out. It’s been that way on every truck I’ve driven, but the newest truck I have is a 1998.

 

So, is it bad? Out of service? Looks like it is from what I’ve been told here.