Isx repairs

Try to hae someone adjust the jakes on it but tell then to adjust it cery tight to the point where its hard to pull out the tool see what that does thats how i always adjust isx jakes and they always work good afterwards sounds like u have a problem with the oil pressure once oil heats up it gets thinner to me it still sounds like some o ring is not sitting right or wasnt changed. When they rebuilt the jake brakes how many orings did they replace did u get a chance to see it

 

Check the ECM power and ground wires. I think that series has 12 volt inputs on 4 wires that split from the original battery feed wire. I have found before where the butt connector went bad and one lead had no voltage. This was actually causing the volt gauge to read low in my case, but if you have a different wire with low/no voltage it could be causing lazy solenoid action. Make sure to load test the power and grounds with a head light bulb. Other than that, you can always try a test ECM.

 

Sounds like worn rocker shafts still.