engine knock

Is the sound coming from the top or the bottom of the engine. From the bottom it could be a wrist pin, or even a big end bearing. Any loss of oil pressure? I would pull the sump and check the clearance on the big ends. Is the sound more or less in sync with the rpm's? I.e fast or slow knock? Some Cummins motors produce a knock from the compressor, but it goes away when the air governor kicks in, and comes back when the compressor starts to pump again.

 

before you inspect crank and rod bearings, check solenoids (bas timing solenoid makes engine nock) and run cyl. cut out test with Insite. It helps localize the faulty cylinder

 

Engine Heads

 

We have had one of our 2007 isx engines do this. It has been doing it for over 150 000 miles. Ive run the overhead twice just to make sure and your right it didn't help it. It runs good though no problems or engine codes. It is in the top end and sounds kinda like ball bearings being bounced arouund off of a wall its a real fast pace beat. Ive either come to the conclusion that it is either the injector popets or somthing with the fuel timing but it isn't any worse so we haven't tried to find it. cummins has looked at it a couple of times and they don't know what it is for sure either but it is kinda of a fast paced knocking noise and not in any really one spot just kinda throughout the top end and noiser over on the turbo side.

 

We had a signature 620 do this - same deal ran overhead , did actuator tests etc etc swapped actutors no difference pulled 4,5,6 injectors and found the lower body nut on the injector had unscrewed itself , fixed the injector resealed the rest and that fixed it we all thought it was a timing problem but could,nt pin point it