Exhaust or jake brake or neither?

[k_jensen6]

How do I know if I have a jake brake, an exhaust brake or is it possible that we don't have either of these? We have a 2001 holiday rambler imperial with an Allison 3000 transmission.

Am extremely nervous going down hills.

Thanks

[mowermech]

" You can stop by your local Cummins or Allison dealer and they will look over your coach and advise you what exactly you have and how to use it properly."

THERE is the best advice I see in this thread! Go to the local experts for some hands-on teaching!

[Executive45]

A word of caution...the exhaust brake should NOT be used in rain and/or snow. Also, usually it will not engage if the cruise control is ON.....

To the OP...when descending a grade, engage the EB as your speed picks up...the brake will engage and the shift PANEL will show 2,3 or 4 depending on how your rig is configured. (a simple adjustment can be made to the computer to change it to whatever gear you're comfortable with) but the tranny may not shift down immediately. If it does not, and you are still picking up speed, hit your service brakes by jabbing the pedal..this will usually cause the tranny to downshift and your coach will slow. Once you get the hang of it, you will rarely use your service brake going downhills. Just remember to use the jabbing method on the brake pedal. You can stop by your local Cummins or Allison dealer and they will look over your coach and advise you what exactly you have and how to use it properly....Dennis

[wolfe10]

We KNOW that the OP has an exhaust brake.

No Cummins C which he has has an engine compression brake. He also said he has literature in his coach about a PacBrake.

[gma77]

Often the distinguishing factor is the button that turns on the brake device. Most often the exhaust brake is an on/off button, and if there is a two stage button it is a Jake (Jacobson) brake. Both are intended to slow up the vehicle and I would encourage you to get acquainted with this device. Generally, we have found the Jake to be more aggressive even in the less aggressive mode in slowing the vehicle up. I have taught RV safe driving in just about every brand, size, or vintage RV motor home. You have two valuable tools to slow you up coming down a mountain as an example. The Allison 3000 can take some speed off by just shifting down. You can't break the transmission because the computer logic won't let you Do use the transmission down and/or the engine braking devices. They will help control the speed on a down hill but you will most likely still have to use the brake to keep you from losing control. One other note, you can leave either of the engine retarders on all the time. Enjoy your RV and safe driving!

[RognBon]

On our '97 Dynasty we have a PacBrake. Ours does not have a switch to turn it on or off. When I need additional braking power, I remove my foot from the accelerator and push the Pacbrake switch with my left foot (it is on the floor right next to the dimmer switch). Just removing my foot from the accelerator does not produce any additional braking power.

[Old-Biscuit]

To use the exhaust brake......turn it on
When you let off the accelerator pedal it will engage (closes...has some method of regulating exhaust back pressure) and you will decelerate. Your Allison transmission will probably downshift also slowing you even more.

When you push on accelerator pedal the exhaust brake will disengage (open) until you let off pedal again.

Great for downhill as it will help slow/control downhill speed.

Turn it ON when you want to use it....turn it OFF when you don't

I use mine whenever towing
I even use it sometimes when not towing
Simple.......push the button

Try it out...see how it works.

[ferndaleflyer]

Well since no one told you----if it is working properly, you turn it on, remove your foot from the accelerator, and you will feel it not only slow down but shift down.....Thats basically how it works. When it is turned off only your vehicle brakes slow you down when applied.

[wolfe10]

Yup, both the engine (Cummins C) and PacBrake tell you that you have an EXHAUST BRAKE.

Which also means you should lube the brake: http://www.pacbrake.com/index.php?page=maintenance-4

[ScottG]

The "Pac brake" is an exhaust brake and a good one at that. Congrats!

[Altern]

Old-Biscuit wrote:
An 'engine brake' is on the engine and controls exhaust valves opening them.....when engaged you will hear a loud pop-pop-pop sound (just like the semis)

IMO this is a bit misleading because most MH's have a muffler on their engine brakes, (aka Jake Brakes) and are pretty quiet. Any pop pop noise is hardly discernable.

Jacobs Company also makes an exhaust brake so both are sometimes called Jake Brakes. If you have an exhaust brake - just call it a Pac brake and no one will be confused.

[k_jensen6]

OP: When we purchased unfortunately it came with no manuals. I did find the original sticker from the window however, it says, Cummins ISC 8.3 350hp Diesel engine. It also says exhaust PAC brake (?). The brake pedal says air brake on it.

The only button I can find on the rig in the driver section says engine brake.

So if this it, how do we use it?

Thank you so much for your help.

[Old-Biscuit]

Your other post said you had an engine brake???

An 'engine brake' is on the engine and controls exhaust valves opening them.....when engaged you will hear a loud pop-pop-pop sound (just like the semis)

An 'exhaust brake' is mounted in the exhaust system and closes it own control valve to create back pressure in exhaust system (back towards engine).....when engaged you will hear an increased exhaust hiss

Both types of brakes have to be turned on........usually a button on dash.

[Pass42]

And there is usually a switch to activate it........

[wolfe10]

Tell us what engine you have-- that MAY give an answer.

If not, easy to describe what an exhaust brake looks like and where to find it.

[HappyKayakers]

You should be able to hear the jake or exhaust brake when you decelerate. Other than that, check your manuals.