1999 2500, 4X4 auto stock... 147K, inherit from Step Dad. Truck sat for about 4 yrs, monthly starting.PacBrake isnt actuating. I can assume it could have frozen (rusted linkage) or a relax/vaccuum issue. Ideas to check? I'm getting light on the powered dash switch, so its alittle more than a grounding issue. Can I disconnect linkage and action it loose?

Hmmm... On my Jacobs Brake the arm is on a heavy spring and takes a lot of force to even move. But I would check the source vacuum at the valve and after the valve to see if the valve is directing vacuum properly to the brake. Are your vents working properly in the cab? (A/C, vents, floor, def)

Are your vents working properly in the cab? (A/C, vents, floor, def)

Later on today I grab a video of my Jacobs brake operation and post it up...

You might try soaking it in acetone and ATF if you can't get it to free up with normal methods. PB Blaster works good too!

I have a PacBrake on my truck, a couple of years ago I hadn't used the brake for quite a while and the butterfly froze in the open position. I had to take the elbow with the butterfly off and disassemble it as far as I could. I removed the butterfly plate but couldn't get the screw on the housing loose to get the shaft out. I ended up soaking the shaft and elbow in deep creep seafoam for three days before I was able to work it loose with a large channel lock pliers. I bought some of the synthetic lube from PacBrake and use it on a regular basis as well as use the brake often to keep it loose and working.You should be able to (with the truck shut off) move the actuator arm on the butterfly shaft with a pliers if it is not frozen. Two other problems that can occur with these brakes: one dirt can stick the electronic solenoid vacuum controller valve that mounts on the intake horn mounting bolt. The solenoid has a button on the end that can be pushed in with the truck running to test the operation of the valve and will actuate the brake vacuum cylinder that operates the butterfly. If it don't actuate the cylinder then either the solenoid electronic component don't work or isn't getting power. The other common failure is the vacuum cylinder is leaking and won't hold a vacuum on the internal piston seal when the brake is actuated. In this case the cylinder must be replaced with a new one from PacBrake it is not rebuild able.If you call PacBrake the techs will email cleaning instructions for the solenoid valve it is quite sensitive as to how it is cleaned without damaging it.