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Lost torque and HP on Grapevine

Yahoo Message Number: 8666
Was climbing hill in 4th at 2000 rpm with max hp and torque. Then start a stretch downhill, so put on the exhause brake (pac brake).
It worked. Then there was a hill ahead so switched off pac brake, but had no get-up and go. Pac Brake dash light was off as expected.
Could not get over 400 (ft-lbs?) of torque or a couple hundred HP.
Lots of black smoke from exhaust. No engine alarms (engine checks). Watching all this on the silverleaf. Pulled over at top of hill. Shut down for a minute. Restarted. Still problems.
Proceeded to brake check area. Shutdown for 5 minutes, checked engine compartment. All visually okay. Restarted. Everything fine.

Have had short spirts of this problem in the past after using pac brake, but usually no problem.

What is the problem? Stuck pac brake? or ??? Is it an engine warranty item or ???
Herb

Allure 2002 #30690 ISC 350

Re: Lost torque and HP on Grapevine

Reply #1 –
Yahoo Message Number: 8668
Herb, I had this same problem with a 2000 Intrigue I owned. It is definitely the Pac brake butterfly valve sticking. They finally replaced my Pac brake under warranty---no more problems. It's a helpless feeling when this happens------one way to free it up is to rock the tranny from drive to reverse and back. Good luck.

Walt Rothermel
03Allure30811

Re: Lost torque and HP on Grapevine

Reply #2 –
Yahoo Message Number: 8680
Thanks for the info. I agree that it is a very helpless feeling.
What warranty covered it? Cummins, CC 1st year, or a service contract?

CC tech told me that the PacBrake needs regular service!!!! What service interval? What needs to be done? He thought something was mentioned in a recent Destination CC magazine.

My Diesel serviceman was quite surprised. He felt the most common problem is a defective relay valve. CC won't touch it at the Tucson rally. Am told that it is not a problem you would take to Cummins.
What does CC do with the problem if someone takes their coach to Junction City?

Any recommendation of service locations around Palm Desert, Phoenix or Tucson?
Herb

Allure 2002 30690

Re: Lost torque and HP on Grapevine

Reply #3 –
Yahoo Message Number: 8681
Mine was replaced under the PacBrake warranty---there should be a booklet in your file you received with your coach. PacBrake gave me the name of the nearest truck garage authorized to work on their eqpt. I did have to pay for labor and then get reimbursed and that took awhile, but it finally worked out.
Servicing these units is difficult. First you have to use a particular type of lubricant, and unless you are a contortionist you have to go thru the hatch under the bed to get to the lube spot. I don't believe the CC techs will work on these units.

Good luck

Walt Rothermel
03Allure30811

Re: Lost torque and HP on Grapevine

Reply #4 –
Yahoo Message Number: 8693
Quote

Quote
Herb: Once you find the solution, please share it with us. I have had similar problems when driving in a hilly area where I wanted a little power, then engine brake, off and on, so that the valve stuck in the "brake" position and the engine smoked excessively and had no power. To preclude this happening again, I chose to not use the throttle when the engine brake switch was activated and I have had no problem since. Assuming it is a maintenance/lubrication solution, I would greatly appreciate a tip on where to service the mechanism.
I've heard many truckers using the engine brake as a form of noise polution, especially when used in conjunction with straight pipes. grrrrrrrr. Therefore I assume some cowboy wannabee truckers leave their engine brakes on all the time.

Larry
Intrigue
10762

Re: Lost torque and HP on Grapevine

Reply #5 –
Yahoo Message Number: 8703
With Jakes and Mack's dynatard, they are generally left on regardless of throttle setting. Some activate with release of the throttle and others require a separate switch. We should be able to leave the Pac brake on without worrying about the valve sticking.
You are right that some cowboy truckers used to use them just to make noise. Like accelerating just before a stop. That is why some many cities have posted "no engine brake" signs. Not such a problem since the big turbos now smother the exhaust noise.
Now I have a question. I thought the Pac brake was an engine brake, not an "exhaust waste gate". Where is the valve that is being mentioned? Doug 03 Allure

Re: Lost torque and HP on Grapevine

Reply #6 –
Yahoo Message Number: 8705
The valve is inside the Pac Brake housing. In my case it was off-center, thus the whole unit was replaced. My present rig has a Jake brake---much better.

Walt Rothermel
03Allure30811