MBN Problems....

I know the talk is power, but what happens to the timing or valvetrain on the MBN motor at 1350 RPM. Mine has a rattling sound from idle up to 1350 unless there is a pull on the motor, then from 1350 on up it purrs like a kitten. The headgasket was blown from 4-5-6 and all 6 injectors where replaced at 475,000. It made the noise then and still makes the rattle. Any help would be great!!! Also have an ECM from a wrecked 6NZ 475/1650 i'm trying to talk our shop forman into putting on.

 

Is it gear rattle? Have heard of the bearing(s) going out on the bull gear.

 

I should clarify. The noise is like a cold injector crack kinda. The sound is the same in every gear as long as there is NO pull on the motor, and if the motor is freewheeling and you crack the throttle it starts to surge or lope but as soon as the motor loads it stops. Also when idling and slowly bring the RPM up when it hits 1350 each and every time you hear a change in the motor AND the truck will rock one time just like you flipped a switch. The cam, compression, front drive, fuel pressure where all checked when the work was done at 475,000.

 

OK. That helps. If it has always done it, it sounds like what mine does, and also what ALL of our Deere tractors with HPCR engines do. It is the computer changing the timing. The Deere engines are worse cold as well. Sometimes can feel a change in power on the Deere engines, but not my Cat.

 

Thanks Bigstretch. I dont have to worry anymore, swapped ECM from 6nz and all my troubles have left the building!!!!!!!!!!!!!!!!!!!!!!! The only thing is my boost feels a little low. Not sure how much (no gauge) but sounds weak. Removed the wastegate pulloff hose and seemed to help. Need to run it a while and make sure. Had to turn off water sensor feed in ECM and the shop told me the power was set a little under what my old ECMwas. If it works fine will reset the power up a little and torgue a lot (I HOPE).

 

I have a 6NZ with a 340B model Jake on it. According to the way I interpret your post, my piston lash setting should be .033"?