How Cruise Control Works With Exhaust Brake

[szakaluk]

In our 2003 Holiday Rambler Endeavor 40PBDD, there are two switches on the right control panel. One enables the "exhaust brake", one the Cruise Control (there is also a separate "set" switch for the cruise control.) Turning on the exhaust brake switch disables the cruise control. This is correct, and seems a good safety feature.

In our (new to us) 2006 Monaco Diplomat 40PAQ, the cruise control switches are on the steering wheel, the exhaust brake switch on the right panel. Regardless of whether the exhaust brake switch is on or off, the cruise control will function OK until the service (foot) brake is engaged, at which time the cruise control turns off, and the exhaust brake activates.

Is this normal? Is it OK to run this coach with the exhaust brake engaged and use the cruise control on the open highway?

Thanks

[wolfe10]

szakaluk,

Welcome to the FMCA Forum.

There is no standard in terms of how cruise/exhaust brakes are wired.

Some do not function at the same time, some do and some trigger the exhaust brake when on cruise if speed goes a certain amount above the set speed.

Of the choices, I like the one you have on the new coach, with the exhaust brake tied to the brake pedal. That leaves you with the exhaust brake in case of an emergency stop, but also allows use of the cruise control.

[kingfr]

Yes it is OK. On my current coach and my prior coach, with the cruise on and the exhaust/engine brake on, the brake would/will activate if we are/were on a long downhill and the speed increased to 5-8 mph above the set speed. Once we slow down to the set speed, the brake goes off.

[hermanmullins]

My 02 Dynasty has a Jake brake. It will not function with the cruise control on. In most cases people will hit their brake when the brake is needed. To activate my Jake Brake I have a button on the floor on the left side of the steering column. When I push the button with my foot it retards the transmission to second gear and holds it there till I release the button. Unit works well every time.

Herman

[wayne77590]

My '08 works the same as Frank's. Exhaust brake is on all the time. Hit the brake and cruise comes off and exhaust comes on. On descents, at about 6 mph over set point, exhaust brake comes on until set point is met. Most of the times it is necessary to stab the brake to reduce speed to set point, then re-engage cruise and unless it is a steep decent cruise will hold it there.

Your situation sounds normal to me.

[huffypuff]

I leave my exhaust brake on in stop and go traffic. It saves wear and tear on the coach and me.

[jleamont]

We have a Jacobs compression brake, when it’s in the ON position and the cruise is on it will activate on deceleration, as soon as the cruise control starts to apply throttle the engine brake shuts down and you accelerate on the cruise, works the same with the accelerator pedal. Honestly it's kind of annoying, when you want to coast on a highway with rolling hills and you have the cruise set it is too aggressive, the transmission will immediately down shift and you are slowing down rapidly. All I can think of is how much fuel that mistake just cost me . I have gotten use to this so I only turn it on when needed. My on/off and high/low switches are on the switch panel amongst all of the other 15 switches to the left of the driver, I relocated both to the positions closest to the left arm rest so when I need them I do not have to search in the panel for them and I can keep my eyes on the road.

Another annoying feature is it cuts off at 15 mph, which when you are slowing down 35,000 lbs. and it disengages you lunge forward, if you are not looking at the speedometer it scares the heck out of you. One thing, it does sound good, when the engine brake is in operation that is the only time you can hear the exhaust, it sounds like thunder along side of you and it turns heads .

[tbutler]

I leave my exhaust brake on in stop and go traffic. It saves wear and tear on the coach and me.

That is interesting because the owners manual for our first coach said that the exhaust brake should not be used in stop and go traffic. This discussion is very helpful. I had a friend who said he drives with his engine brake on all the time. With our coach that kills the cruise control. So now I know that there is a wide variety of how the two systems are linked and can be operated.

For myself, I consider brake use to be a waste of energy. Make no mistake, if the brake is needed, I use it. Using the brake means that energy (gas/diesel) is being wasted. If you can anticipate conditions where braking is going to be needed, take your foot off the accelerator or shut off cruise control and coast to reduce speed before applying the brakes. I've read that some people want to top a hill at the speed limit which only means you will be on the brakes all the way down the hill on the other side. I try to drive so that I need only minimal braking if at all possible. Traffic conditions sometime dictate that you keep up with traffic and that will increase brake usage but whenever possible minimizing use of the brake will maximize fuel mileage.

[huffypuff]

Hello Tom,

Like I said I leave the exhaust brake on in stop and go driving. What it does is let the exhaust brake and transmission keep the speed down if I need not to hit the brakes for small 4 wheeler cutting in and out. It cancel the cruise control and shut off below 15 MPH. I haven't noticed any loss in fuel mileage other than what you would lose in stop and go driving anyway. The exhaust brake do not turn on the injectors but rather may be turned off. Otherwise I use on steep grades again to minimize having to hit the brakes. This save the brake shoes from excessive wear and the drums from excessive heat, hot spots and warping. If I didn't use the exhaust brake or foot brakes going down grades the coach would speed down the grade like a runaway freight train.

I check my owners manual and it states nothing about when to use. It does state that you may have to manually downshift the transmission if there isn't enough exhaust braking as it depends on engine RPM. I drive conservatively and know if leaving lots of space in front of my coach can get you cut off. I can show you a video of myself cruising at 60 MPH on I-10 and getting cut off by a double tractor trailer. There are lots of wackos out there so I rather be safe than sorry.

[wayne77590]

I leave my exhaust brake on in stop and go traffic. It saves wear and tear on the coach and me.

I'm just the opposite. I leave mine on - according to manual - and turn it off in city driving. The reason stated was to keep the pads from shelacing. I have pads on my MH. So far on my annual maintenance checks there is no shelacing and after 50,000+ miles Freightliner Technician said I have 60% brakes left - no need to change them.

[huffypuff]

LOL Wayne I'm not talking about city driving as the exhaust brake won't work until over 15 MPH. Stop and go traffic I'm talking about is like I-5 going through Seattle, Portland or other major cities that have a freeway going through it. I don't think I ever took my coach on a city street. Normal driving on a highway can be a pain with the exhaust brake on with fuel economy. I find that every little hill it coast down the exhaust wants to come on and I won't be able to use the cruise control. Stop and go traffic and down steep grades I leave it on. All other times I leave off. I'm still saving on my brakes.

[wayne77590]

Well dang! I-5 is mostly "stop!" We prefer to not take the freeways when possible. The means we do have to go through some one-horse-towns, and sometimes several stop lights. Those times I do shut the exhaust brake off, but truthfully sometimes I leave it on. Depends on if the wind is blowing up or down. :-)

I have takin' the short cut through San Fran and across the GGB. Don't remember if I left it on or off as i was kind of busy with the wheel doging those city drivers.

Hey, The 101 is just as bad. Left Oceanside, CA, headed to Porty Hueneme, CA, all of a distance of 156 miles and it took 5-1/2 hours on The 101. Go figure. I did leave it on then. Never knew if you were going to be doing 55 for 1/4 mile or stopped for 15 minutes.