brakes locking up and no brake lites

If you really haven't driven it much there just could be a bunch of rust build up on both the drums and the shoes themselves making the braking surfaces ultra sticky. On the fire wall you will have a brake switch and a cruise cancel switch. If you did get the right switch, check the terminals inside the connector body for any corrosion or spread terminals.

 

one break or all?

could be s-cams

 

Exactly. Go under with a bar and move all your push rods/and s cams. If they move easily, (and they should, other than overcoming the spring tension) then you know its a different problem. Some times if a truck sits for a period of time, and hasn't been properly greased, the s cams will begin to get sticky in the bushings, and then when you drive it, you have dragging brakes. Start here, and work your way forward.

 

OP said the truck slid into the junction...............so that would mean all S cams go bad at the same time.
Not likely.

OP has been driving the truck for a month so cannot be the problem.


OP,footvalve or another valve in the chassis gone bad.
Simple way to check.
Put a pressure gauge on the line going to the brake.
My guess is you will see that gauge go very high as soon as you put your foot on the brakepedal.

 

well slid into the intersection doesn't necessarily mean all breaks were locked up one corner could have been locked up and the rest still turning. if all locked up i doubt he would have gone into the intersection his face would have been in the dash. that's why i asked how many were locking up. one or possibly two locking up and skidding before all the others could very well be s-cams. all not likely.

 

just off hand it sounds like your steers are grabing before your drives.. why I wouldn't know..

 

If i remember right from my days working at a kw dealer as a mechanic. Not sure of internationals. But there is a proportioning valve that works in conjunction with abs system. Not sure the date it was mandated for implementation. If faulty would lead to rear drives or drive wheel end locking up. Also maybe a problem with treadle valve assembly. There is different braking requirements needed when pulling a trailer and bobtail. Proportioning valve is responsible for sensing that depending on the positions of the mv3 valve (parking brake valves). I'm almost sure it's one of the 2 valves but without seeing your trk and how brake system is configured it's hard to say for sure. Hope this gives you a direction to start troubleshooting.

 

Where is this proportiining valve located im having same issue with my t800 dump truck