1998 Western Star. Detroit 60 series. Jake brake has nothing in switch position 1 (guessing it does middle jake). Switch position 2 works (front and rear sections?). Switch Position 3 has the same sound/ feel as position 2 (assuming front and rear are only working?). We've got the valve cover off right now replacing the valve cover gasket and bolt/grommets because of oil leaks. You can't get the brakes to come on sitting in the shop idleing, I'm wondering if I can just take a hot wire to the middle sector, with the engine not running, and see if the solenoid works. Don't want to fry a ecm. Is there a test procedure that doesn't require me driving a hour away to someone to hook it to a computer?
I think if you apply throttle and then let it snap back to idle the brake will engage, same as speed shifting.
The older Jacobs you could push down on the spool of the solenoid with a screwdriver and it would bark at you. I would assume the PAC brakes work the same. May be a loose wire or an o-ring out letting oil pressure bypass. Should be able to rev it up and let off to see which apply. May sling a little oil with the covers off but not terrible. All the detroits I've owned or worked on had wiring issues in the head or injector harness, could have a broke wire somewhere. Nothing you need a computer for. Just a meter to check wires and a small screwdriver to push spools. Junkyard
Remove the lead to the center solenoid, use a jumper wire from the + side on alternator and touch the terminal on the solenoid. You should hear a click. Check the solenoid where it's crimped on top. Make sure there is no slack or loose where it's crimped. Check and make sure the oil galley plugs are all inplace and tight, they can get loose and fall out causing oil pressure loss in the jake. As said above flip the switch on full and run the rpm up to 2000 and let off the throttle to see if the jakes work. The jakes automatically shut off at a 1000 rpm so it won't kill the engine. Series 60 engines always had problems with the injector/jake harness. Mainly oil creeping under the insulation. If you run it with the valve cover off just comb the oil into your hair and go set in a 57 Chevy. You can idle it for a few seconds but don't raise the rpm too high. Truck Shop
Dove into the wiring a little this afternoon. The wire to the center solenoid just fell off the spade connector. Installed new connector, but I got out the tester. For some reason, with or without the key on, engine not running, and the jake switch in any position, I have 5.8 volts coming to the center bank only (the one I think has problems). If its got 5.8 coming to it, the solenoid must be bad, or it would be on all the time? Wiring harness? ecm? Get it running with the cover off and see what happens? Thanks for the advice so far guys.
Pull the wire off all 3 solenoids and check the ohms to ground. The 5.8 volts sounds like the ECM solenoid check signal. If you are reading volts on that solenoid, it may be an open coil that's not completing it's circuit to ground.
When I get to the shop in the morning I will check my Series 60 manual for the jakes. Truck Shop
You mean you have 5.8 volts coming to the solenoid with all the wiring hooked up? If there is a phantom 5.8 volts on the wire open circuit then it should drop to almost zero immediately on hooking up the wire. If it stays up as a phantom voltage then the solenoid coil is probably open or not grounded or something. Further investigation needed. What is the resistance from the hot lead of the solenoid to battery ground?
Oh, it was a winner of a day today. I didn't get to this thing until today, the trailer section details my fun weekend fighting a wheel on the trailer, but I got this sorted out today also. Disconnected the wires from all three brakes. The other 2 pac brake control wires, have voltage (around 3-4 volts) coming to them also, when disconnected from the solenoids. Hot wire tested the solenoids (12v applied to them). Only the back brake solenoid works. What I thought was 2 brakes, was actually only one activated. Removed the two bad solenoids, one had a bad gasket in it also. Two more should be here tomorrow. Thanks everyone, I'll report what the new solenoids do, but if I've got three times the braking I thought I had, I'll be happy indeed. Thanks again