|
First off, is it a "Jacobs" brand exhaust brake we are talking about here? If it is some other brand, the following may not be applicable.
It sounds like your air pump that actuates the butterfly valve may have stopped working. This is the most common reason that they don't activate. Another could be that the butterfly valve is carboned up and can't rotate to block the exhaust, even if the air pump is working.
Can you hear the air pump kick in when you pull the knob up when the engine is below operating temp? If not, the air pump is the likely culprit, be it a mechanical failure of the pump itself, or a wiring/switch/fuse problem that is not allowing the pump to do its job(I can't recall for sure if there are any inline fuses in the wiring, or not).
|