ISX 870 jake brake issue

[Rawze]

(07-09-2019 )Jose9640 Wrote:  I have an issue with the jake brakes on this 870. Hit the switch to level 3 and you can hear the jakes come on but very very weak. If I go to level 1 or 2 it feels exactly the same. I hooked up insite to the truck but there was no codes for jake brake. What should I look for? Insite showed 33% on level 1 67% on 2 and 100% on 3

Chamberpains is spot on.

some things that come to mind, listed in no particular order here...

Wiring and solenoids are common culprits. They will not always throw a code for this.

Next would be the mechanics of the jake rockers. things like the their built-in actuators(pistons), etc.

Next would be the oil pressure in the head. If it is weak, then the jake will be weak. Check the overhead cams for excess wear, and check the oil pressure is 34+ for the engine going down the road.

Next would be the wear in the rocker bearings. if there is excess wear in the rocker bearings, or the rocker shaft(s) then it will significantly lower oil pressure to the upper part of the head.


Also can't forget that the ISX uses the turbocharger to increase its effectiveness of the jake brakes by making the turbo produce high amounts of exhaust back-pressure. If there is any issue with boost or manifold leaks or with the turbo positioning/pressures being correct, or if the turbo exhaust impeller is damaged or worn down from carbon packing then it will effect the jake brake directly. It will also usually effect the boost pressures for the engine too by some degree. A proper boost gauge is your best friend in any turbocharged diesel engine.