Have a 2000 w9 430 detroit. For first few miles and minutes of running, all 3 stages of jakes work properly. But after few miles down road it almost loses the third stage. I can select back and forth 2 and 3 stages and it makes very slight noise change as well as about 2psi boost difference. Back in April, had a injector termial to break and shop replaced that and one jake they said had a broken bolt/spring. (can't remember exactly as i don't have reciept in front of me now but was $400 part) Picked truck up and did perfect for a while now it's back to same as before. I pulled valve cover off and can see new jake but do not know what bolt/spring could be broken. Is there common part that breaks in jakes or maybe a wiring issue??? Makes no sense it works when first going then quits. Truck has smart wheel too. Truck is also not driven much
Mine did the same thing when a spring broke in the pacbrake. There are 12 springs total and it was decided at the time since the valve covers were off and one of them was weak enough to break (was close to million miles) might as well go ahead and replace all the others too. They're not expensive and labor is only a couple of hours or so.
