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Logthumper · 05-18-2008, 10:27 AM

2007 Monaco with Cummins ISC 330. With the cover off the engine compartment, engine running, shouldn't the Exhaust Brake Air Cylinder operate (extend) when the Exhaust Brake Switch is operated? If not, what procedure needs to be done to observe if the Exhaust Brake is in fact closing when the Exhaust Brake Switch is engaged?

The Butterfly is not stuck, it can be moved by hand.

On the road, a down Shift does take place, but not much braking action.

On a previous diesel I had, with engine idling, a definite change in the exhaust sound occurred when the exhaust brake was activated and exhaust back pressure built up.

Will check with Monaco Tech Support in the morning, but I,m betting that better info/experience is here.

Thanks

Logthumper · 05-18-2008, 10:27 AM

2007 Monaco with Cummins ISC 330. With the cover off the engine compartment, engine running, shouldn't the Exhaust Brake Air Cylinder operate (extend) when the Exhaust Brake Switch is operated? If not, what procedure needs to be done to observe if the Exhaust Brake is in fact closing when the Exhaust Brake Switch is engaged?

The Butterfly is not stuck, it can be moved by hand.

On the road, a down Shift does take place, but not much braking action.

On a previous diesel I had, with engine idling, a definite change in the exhaust sound occurred when the exhaust brake was activated and exhaust back pressure built up.

Will check with Monaco Tech Support in the morning, but I,m betting that better info/experience is here.

Thanks

SacsTC · 05-18-2008, 11:06 AM

This was taken from a 2006 TechTip:
"While working on the Pacbrake Exhaust Brake in the engine compartment you can disconnect the power wire off the Pacbrake solenoid to power up and to open and close the Pacbrake exhaust."

So my answer to your question would be yes.

Logthumper · 05-18-2008, 11:28 AM

Thanks SacsTC:

I would like to know what conditions need to be met so that the MotorHome is in fact sending the correct voltage to the selenoid. Then if the air cylender does not extend, I can check to see if there is in fact voltage at the solenoid plug.

ronboc · 05-18-2008, 12:08 PM

I am very curious to hear what Monaco has to say, and also what you find/determine yourself. Happycarz's story is also very intriguing.

My PacBrake had been sticking from new, and it took a Cummins Shop to finally decide that it was. They crawled around underneath to do something (I really wish I'd been under there too, but they only had 1 creeper and I wasn't even supposed to be in the shop-area to begin with), but I couldn't see what they did to force an engagement of the Pac. I think the guy said he had to jumper across some pins at the connector (doesn't sound right, tho), but he finally determined it was froze-up. To 'prove' there was a problem to Cummins initially, I had to take them for a drive and show that there wasn't any different braking action when manually downshifting to a stop versus when 'using' the Pac-Brake

Maybe the Tech-tip means to energize the solenoid with external 12v? Or does it imply that just removing power will allow it to engage (ie, fail-safe to ON)?

Hope you get it solved soon.

.

Robin_M · 05-18-2008, 06:29 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">but I couldn't see what they did to force an engagement of the Pac. I think the guy said he had to jumper across some pins at the connector (doesn't sound right, tho), </div></BLOCKQUOTE>
Sixpack has rigged something up to do that, but I don't know the details. Maybe if he reads this message, he'll fill us in. I'd imagine you could just use one of those engine starter switches that mechanics have, connecting one end to the solenoid 12v feed wire, and the other to a constant 12v source.

You've got to keep those dang things well lubricated and you've got to use them frequently to keep them from binding up. I checked mine out and have no idea how I'm going to lubricate it. It's near the top of the engine, but I can't reach it from the top hatch in the bedroom because it's covered by a large metal plate.

Happycarz · 05-18-2008, 09:03 PM

Logthumper,
On many years, the exhaust brake won't engage under a certain speed or at idle. To test yours, follow the wires from the air solenoid until you find a connector. Unplug it, using the pigtail that goes to the solenoid, take either lead and ground it. Apply 12v to the other lead and watch the PacBrake for movement. Another way is to open the bedroom hatch and watch as someone drives the coach.

Logthumper · 05-19-2008, 12:26 AM

Happycarz: WOW! You are up in the middle of the night also. Its 4:00am now and I've been up prowling over schematics and installation info for the Exhaust Brake for at least the last hour. When I want to know if/how something is supposed to operate, it just drives me nuts until it makes sense. It looks like the Exhaust Brake is completely controlled by the ECM, so I want to make sure the "system" is operating as it is supposed to. I can make the Air Cylinder operate by applying 12 volts to the Air Solenoid, but that doesn't tell me if it is operating as it is supposed to under system control. Would love to have the wife drive while I watch the Exhaust Brake but we have the side bedroom slide and when closed covers the motor hatch. If the system is not operational on a "test" basis (info from Monaco Tech Support in the morning), I'm going to attach a wire to the "purple" wire going to the Air Solenoid and connect a 12v LED from it to ground which will light when power appears or make a "scratch pad" gadget to attach to the Air Cylinder and then drive the unit. If there is Exhaust Brake activity, its movement will be recorded on the "scratch pad" for checking.
Thanks to all for the support.

Roland · 05-19-2008, 04:21 AM

Hello Logthumper,
My understanding of the operation of a Pac Brake is that the following conditions must be met for the unit to engage.

Unit turned on.
Speed less than approx. 63 mph.
RPM's greater than 1300 RPM.
Trans must be 2nd range or higher.
Throttle Position Sensor (TPS) = to 0 degrees.

The above applies to Pac Brakes installed for use with an Allison MD3000MH series or an MD3060 series trans.

Please note that some Monaco units (mine included) are wired so that if both the PAC Brake and the cruise control are both turned on (and you are currently in the cruise mode) the PAC Brake will not engage when you remove your foot from the throttle (TPS=0). You will have to either depress the brake pedal or hit the "cruise cancel" switch. The above also does not apply to units equipted with either a foot switch (Floor mount) or a switch mounted on the brake pedal.

Logthumper · 05-19-2008, 11:48 PM

Roland: Thanks for the info. If the Throttle Position Sensor = 0, but the Engine RPM's must be greater than 1300 RPM. Then it looks like the Exhaust Brake would not operate (tested while standing still) unless the coach is rolling at a speed fast enough to create the 1300 RPM. Had no time to look further into this today.

Update: Tech Support Confirmed today that coach must be rolling to test Exhaust Brake.

Roland · 05-20-2008, 05:58 PM

Hi Logthumper,
To find out if your exhaust brake is working take the coach out on a highway (level road or down hill), get it up to about 55 to 60 mph so that you are in 6th range.
Remove foot from throttle.
Allow coach to decelerate.
Watch your tachometer for increase (small increase for 6to5 shift - larger uptick for 5to4 and lower) during downshift. If you have a two window Allison shift pad display you can see the "gear attained" window change numbers at the same time. Also with the drivers window open, you should be able to hear the exhaust noise (loud hissing sound) when the exhaust brake butterfly valve is closed. Tap the throttle during deceleration to hear the noise change as the valve opens and closes.

Hope this helps,

Happycarz · 05-20-2008, 06:26 PM

Logthumper,
Don't be fooled by the 12v LED. That was one of my tests. It did light at 11.2v, but 11.2 will not open the solenoid. My friend's Scepter gets 10.9v and it does open the solenoid. I'm back to swapping coils with an air dump solenoid to see if 11.2 v will pull that one in.

Monaco sent me a partial wiring schematic showing the exhaust brake switch that feeds the ECM and a relay that feeds the TCM, but not any of the circuit to the solenoid relays or the solenoid. I emailed them my concerns last night and had no response today.

Camelot Camper · 05-20-2008, 06:30 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Logthumper:
Will check with Monaco Tech Support in the morning, but I,m betting that better info/experience is here. </div></BLOCKQUOTE>

You're right!!! The info/experience here is much better. If fact, I haven't called Monaco Tech Support since finding (thanks to MM) this super forum.

CC

Robin_M · 05-21-2008, 02:43 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I emailed them my concerns last night and had no response today. </div></BLOCKQUOTE>I wouldn't rely on email to Tech Support. Sometimes they answer and sometimes they don't. I think email is the last thing they look at, if and when the phones stop ringing. With the lay-offs, I'd guess that situation may only get worse.