Community Forums

whitetop · 04-10-2016, 07:12 PM

Can someone please tell me how to check to make sure both engine brake settings (compression brake) are working. When going down a incline the brake comes on when accelerator is lifted but brake does not feel any different when switched between Hi/Lo settings. Is there a troubleshooting method available? Thank you in advance for any replies.

Doc Mark · 04-10-2016, 07:49 PM

There is a definite difference in sound and feel when I use the low vs high engine brake settings. The engine revs higher in high braking and there is a greater feeling of deceleration. I know of no test that you can use but I bet others will have a solution for you. Good luck.

Mark

whitetop · 04-12-2016, 10:59 AM

Wow looks as if I'm going to have to keep on researching this and post back what I find. It may take a bit because I'm still currently working 50 hours a week. But I will follow up at some point. I'm still open for suggestions though...

Rich-n-Linda · 04-13-2016, 08:36 PM

There will be no difference in engine revs between the high and low setting. Just a slight change in braking force, and sound.

whitetop · 04-14-2016, 06:56 AM

Thank you Rich. That is something I will need to pay attention to and determine if there is a difference. I am currently trying to figure out the wiring (from switch to solenoids) and operation of the system, but have not made much progress

DMTTRANSPORT · 04-14-2016, 07:11 AM

First off it's not a compression brake, the over head Jake/Pac Brake hold the exhaust valves open (like turning the key off) you can tell the difference form 1-2 by a slight roughness from the Engine when only one bank is being used (3 cylinders) as opposed to all 6.

Gary RVRoamer · 04-14-2016, 08:20 AM

Mine isn't noticeably different while still in a higher gear - the difference in slowing rate becomes more apparent as the transmission shifts down. Be aware that the tranny selects a lower gear right away, but does not actually downshift until it can do so without pushing the RPMs too high. So at 60 mph, you are still in 5th or 6th gear even though the selector may say 2 or 4. In 6th gear, there isn't a lot of engine braking whether "full' or "half".

rmbarr · 04-14-2016, 08:50 AM

My un-conventual method is in going down hill with exhaust brake in either mode, find the speed that the braking will maintain relative constant speed, then change (either low or high), then change modes and watch the coach speed change.

DMTTRANSPORT · 04-14-2016, 10:07 AM

Quote:

Originally Posted by rmbarr

My un-conventual method is in going down hill with exhaust brake in either mode, find the speed that the braking will maintain relative constant speed, then change (either low or high), then change modes and watch the coach speed change.

Your doing it right! Ice/Snow would be a different scenario...

Pusherpilot · 04-14-2016, 10:50 AM

Gary and rmbarr have it right. I've made it to the bottom of the Grapevine on I-5 without using the service brakes on many occasions. One of the tricks is never go slow enough to want to shut off the Jake and never let it get going fast enough to prevent a downshift to 4th gear. I had the brakes checked last year and at 100+k miles i still have well over 50% left on them.

whitetop · 04-14-2016, 11:05 AM

Thanks to all of you for the replies. What has been mentioned here is exactly what made me think that only one of the positions is working. When going down a grade there is not a noticeable difference in either position. Although the brake does function, I feel it is in the low position and that is what I would like to determine. I am trying to figure the power trail and the solenoids. Please keep the good information flowing.

Skip426 · 04-14-2016, 11:34 AM

Your Hi/Low ( 1/2 ) engine brake switch , signals the Cummins ECM , what stage of engine brake is selected , and the ECM, controls the mechanism , under the valve cover, to use either 3 or 6 cylinders for engine braking.
NOTE: some engine brakes are 3 stage , using 2/4/or 6 cylinders for the task.
The mechanism uses engine oil pressure to work the valves and provide the hold back. Some members have reported a low oil pressure warning when the engine brake was in use, an indication that the mechanism was in need of repair. If you feel no difference in the amount of hold back and hear no difference in engine sound , check the oil pressure gauge carefully, there could be an oil seal in the mechanism's second stage in need of replacement.

Dutch Star Don · 04-14-2016, 12:09 PM

"whitetop".....Here is another test that might give you some indication that it's working properly. Test it on a local roadway. Set it on LOW at about 30 mph and let off the throttle. Then compare it to HIGH doing the same thing. On mine, it wants to pitch you through the windshield on HIGH.

whitetop · 04-14-2016, 06:53 PM

Thanks to all for the information. I will try both suggestions, monitor oil pressure, and a road test. Both are great ideas and sound advice. I am trying to find out if there is an exterior solenoid that controls the position of the mechanism in the engine that I can check? I have checked the selector switch already.Thanks again I do appreciate your replies.