Brake System

[Fred Cook]

Still trying to learn my coach. I did not have a braking system other than service brakes on my previous 1990 Barth DP so I have no experience with Jake or PacBrake. My switch says Jake Brake on it but I understand that Jake makes an exhaust brake too. So which one do I have on my C12... a compression or an exhaust Brake? Thanks

[Gerald Farris]

Fred,
Your C12 has a 2 stage compression brake. 

Gerald

[David T. Richelderfer]

You will soon learn how and when to use your Jake Brake, and you will love it.  I almost always have my Jake set on the higher braking setting.  The Jake really shines when slowing down entering a limited speed zone or holding a speed on a downsloped highway without using or only intermittently using the footbrake.

One thing you might check on is your Jake/Allison programming.  Our coach was programmed to shift automatically to 4th gear when the Jake activated.  I had ours reprogrammed to not automatically change gears.  It took only a couple times for our engine's RPMs to go from 1,500-1,600 RPMs to over 2,200-2,400 RPMs in about 1/2 second to scare me.  I like the manual control of downshifting, not the automatic downshifting.  I had ours reprogrammed to not automatically downshift at all, but you can get it reprogrammed to downshift automatically to 5th gear or 4th gear.  We stopped at the Kenworth Truck Repair shop in Pasco, WA for reprogramming.  It takes only a few minutes once the computer connection point is located, which on our coach was under the dash plate.

[Lee Welbanks]

Yeah, first thing is to reprogram the trans not to shift down, also had mine done at KW in Pasco, Wa. And like David states downshift yourself as needed.

[Fred Cook]

Thanks for the responses.  From what I have been reading, having a Jake compression brake is a better option than having an exhaust brake.  I don't have a manual so I have been learning on my own.  What I have noticed is when doing down a steep grade at high speeds I push back on the switch to slow the coach down but not coming to a stop.  When I push forward on the switch it tends to want to slow down to a stop, which is good coming off a ramp and also in city traffic.

[David T. Richelderfer]

Yes, it's a two-speed function - three cylinders and six cylinders, I believe.  If the hill you're going down is steep or you're approaching a limited speed area, then use the high braking switch position.  If the hill is not steep, then change to the low braking switch position.  Again, I almost always leave the Jake switched to the high position for convenience and safety because the instant I pull my foot off the accelerator pedal, the Jake will be fully functioning before I can get my foot on the brake pedal.

[Keith Moffett]

Fred, it is not good for the jake to ride it to a stop.  It should cutoff at about 12 mph .  Use the service brake to stop fully.  To highlight what is mentioned above about auto downshifting, the RPMs shouldnt be over 2200 due to possible damage to the engine.  This from the manual in our 02 Marquis with C12.

[Fred Cook]

Fred, it is not good for the jake to ride it to a stop.  It should cutoff at about 12 mph .  Use the service brake to stop fully.  To highlight what is mentioned above about auto downshifting, the RPMs shouldnt be over 2200 due to possible damage to the engine.  This from the manual in our 02 Marquis with C12.
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Thanks for the tip Keith. I will keep an eye on it.

[Fred Cook]

Well.... just have one question. When the Jake brake is on, are the rear brake lights come on too?

[Gerald Farris]

Fred,
Most, but not all coaches have the brake lights connected to the Jake brake circuit. On my 2000 Marquis, the Jake brake did not turn on the brake lights, but on my 2002 Solitaire it does. So the answer to your question is maybe.

Gerald 

[Fred Cook]

Thanks Gerald... I was hoping I didn’t ask a dumb question. LOL

[LaMonte Monnell]

Thanks Gerald... I was hoping I didn’t ask a dumb question. LOL

There are no dumb questions on here Fred! If so I have asked most of them by now!

Hope you are figuring everything out.

I am still wrenching most everything I can.