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CUMMINS ISX CHOPPY JAKE BRAKE

44K views 13 replies 5 participants last post by  trucker378 
#1 ·
I have a 2006 ISX 450 and the jake brakes sometimes run very choppy and rough, enough to shake the whole truck somewhat violently. The problem comes and goes but seems to be warm weather related. It happened a lot last summer and stopped completely this winter and is returning now with the mid 70 degree temps here lately. My truck has the low-med-hi switch for the jakes and is the two solenoid system. It seem to act fine on the low setting so I am thinking the problem is somewhere in the #3 solenoid or circuit (#1 not used on this engine.) I replaced the jake wiring harness thinking that would fix it because there was oil in the pass-through connector on the side of the head but its still happening. I've also replaced both solenoids, both rocker shafts and some of the rockers (not sure which ones.) The problem usually starts after a few hours of running and after a hard pull and then comes and goes the rest of the day. It seems to be affected by oil temperature which is in turn affected by outside temperature and engine load.
Any ideas?
 
#3 ·
overhead has been run several times since problem started. Head was replaced also because of leaking injector cups. so naturally overhead was run then too. All I can think of is oil dripped down into the outside harness, or a bad jake rocker or the saddle that the solenoid screws into.
 
#4 ·
What oil are you using? Some thinner synthetic, like a 0w40 or 5w40?
 
#7 ·
I run insite but it is not picking anything up. Have had the truck on the dyno multiple times and done a 2 hour ride along with cummins rocky mountain lead technician. We could not duplicate the problem. It takes a load, warm weather and several hours of running before the jake problem starts.
 
#13 ·
Finally got this fixed two weeks ago. Jakes have been smooth ever since :) The problem was the result of several issues: Two of the front jake rockers had excessive wear and were leaking oil past the rocker shaft. The strange thing is that the jake acted fine on the low setting which is when the front rockers are used but got choppy on the med/hi setting which uses the rear rockers (recently replaced.) Agrivating the situation was a small leak at both solenoids plus oil getting into the BRAND NEW wiring harness at the pass through connector. These problems were all caught thanks to a mechanic who took some time to run the engine with the valve cover off and manually run the jakes so he could see where the problem was. Cudos to that mechanic at Cummins in Kenner, LA
 
#12 ·
As hot as the engine oil runs on the ISX, I wonder if things are just getting too hot? Solenoids don't like a lot of heat generally. Wonder if adding another external oil cooler would help.

Cummins says 225* is normal for the oil temp on them, but I like the 150-180* oil temp in my Cat far better. :D
 
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