Parking brake doesn't always release

[Fredward]

Looking at the schematic in the manual, I am looking for the "Air Pressure Protection Valve" and it is located in the "Front Wheel Housing". It appears to provide lower pressure air to the three ride height valves and to the Parking Tank. The parking tank is one of the two tanks located in the front wheel housing. And the Parking tank is connected to the push-pull valve and the inversion valve.

I guess I'll take some more wheels off!

[Fredward]

OK I think I'm getting somewhere. The regulator appears to have been removed by a PO.

Judging from the parts manual, we need the "Pressure Regulating Valve - Parking Brake" part number 3C-34-37. Someone put in a quick connect fitting and a section of hose between the "Filter" and the parking tank check valve.

Also I know which DD-3 hangs up so I know where to look each time too.

[bevans6]

The pressure protection valve is a completely different valve that does a completely different thing.  It separates the service brake air system from the rest of the air system (the emergency/parking brake tank, the auxiliary tank and the suspension).  It is designed to close if the air pressure in the service brake tank (the dry tank) is less than 60 psi.  this is so if a leak in the suspension or the auxiliary  is draining things down, the valve closes and retains at least 60 psi in the service brake system for a couple of brake applications.

Brian

[Fredward]

OK. Well everybody seems to be of the opinion that I need 85psi air to the parking circuit and the guys at C&J said their is usually a regulator located back in the rear wheel well or on the axle along with the inversion valve. SO I got the regulator from C&J and installed it on the rear bulkhead right where the air line transitions from copper to rubber hose. So far So good. I set the regulator at 85 psi and can't get the DD-3 to hang up anymore.

Upon close inspection, it looks like maybe some kind of regulator mounted right to the bulkhead but I didn't want to mess with removing, cleaning and maybe rebuilding it. So I just attached the new regulator to that old whatever it is and made everything look good.

We're heading to Rhode Island and New York area in a couple of weeks so I guess that should be the real test.

THanks for the information guys.

Fred

[bevans6]

Glad it's working out for you.  Brian

[Brian Diehl]

Good news!  Thanks for sharing.