exhaust brake

mtrumpet wrote:
Ok, here's another question regarding something that I came across when looking for the info that I posted in my previous post in this thread. (I see that the page that Dennis had posted also refers to the same.)

Two excepts from my Jacobs Exhaust Brake Owners Manual:

Before starting your engine, make sure the Jacobs Exhaust Brake dash switch is in the OFF position.To activate your Jacobs Exhaust Brake, turn the dash switch ON. Whenever you need to slow your vehicle, the Jacobs Exhaust Brake will be active only when your feet are off the clutch and accelerator pedals.During vehicle operation, the Jacobs Exhaust Brake dash switch may stay ON. Your Jacobs Exhaust Brake will activate after removing your foot from the accelerator and clutch whenever the dash switch is ON.

Before shutting off your engine, always turn your Jacobs Exhaust Brake dash switch OFF. Your Jacobs Exhaust Brake should also be turned off when the engine is left idling for an extended period of time (longer than 3 minutes).

My question is, WHY? The exhaust brake is not active or activated when the engine is idling. So what difference does it make if the switch is on or not? All along, I've been leaving mine "on" all the time. The only time that I shut my exhaust brake "off" is when I'm on the highway (or going through towns that don't want you using your engine brake). Does anyone have any idea why they might want us to turn them off when starting, idling and shutting down the engine? (Clearly, I missed that when first reading my owners manual when I brought my rig home for the first time.)

mtrumpet,
I really don't know why they, Jacobs Mfg, would want the exhaust brake switch to be in the off position for starting or, shut down. I too have left mine on for about 99.99% of the time we've owned the coach which, is about 3 years now. And, not sure if you know this or not but, when a city or, municipality posts signs requiring "Engine Brakes" to be disabled in certain parts of their jurisdictions, it's the actual "ENGINE BRAKE" design, that they want restricted, not the "EXHAUST TYPE" brakes. The engine brakes, especially those of yesteryear, were horribly noisy as you may recall.

But, with todays better muffler systems, you could use those all day long in those jurisdictions and never get cited for it. But, that's beside the point here. As for the requirements in the manual for e-brake switch to be in the off position during start up, my guess is that if it malfunctioned, as in staying in or, putting itself into the closed position, you might have a starting issue. But, as you've read and, know by experience, the e-brake cannot activate until you foot is COMPLETELY off the accelerator pedal.

The throttle or, pedal position switch sends info to the engine ECM to let everyone know that, it's either being stepped on or not. Hope this helps some.
Scott