engine knock

T

TRUBBS

Can You Keep Up?
Joined
Feb 15, 2009
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truck started knocking yesterday, had it outside warming up when to leave, put it in reverse and went to back up, started running rough and kinda shaking. put it in netural and reved it up and it started knocking away. when running it sounds like a grinding/knocking from the front cover area, but when you turb it over with the fuel shut off killed you can hear it "thumping" in the pan. im thinking either spun main or shot thrust bearing? what are you guys idea's on what it is and best/worst case senario's? got the motor pulled tonight but havent got anything pulled apart yet.

motor is a '94 with 200k+ on it. ran perfect and had no white smoke from the cap.
 
Try to diagnose the simple stuff first:

Do you have an auto? TC bolts can work themselves loose. Mine did a few months back and it was a really bad knocking sound that changed with rpms at first, then was consistently doing it.

Is your KDP tabbed? I hope so... I haven't had one fall out into the timing case but it happened to a friend of mine. He said it was a horrible knocking that turned into grinding that turned into a huge pool of oil on the ground.

These are just a couple things that came to my mind.
 
Sounds like you already pulled the motor..... let us know what you find, or don't find....
 
yes motor has already been pulled. kdp is take care of.
bad news is- i cant find anything wrong, main/rod bearing's look fine, cam retainer dont move ect.

only thing i can maybe think of is maybe the timing slipped?
 
is their any way to check wrist pin without acrually pulling the crank/pistions out?

cylinder walls all look good and so do the tops of the pisitons also.
 
I would suspect it jumped timing??? I always use the locktite and the 3/4 inch impact to lock the gear on the pump. I have torqd to cummins specs before and had nothing but trouble... If you wipped a lifter it will make a knocking sound as well. i cant explain the noise at the oil pan but.. the botom end of the cummins is pretty tough. If your not pulling 4 grand every shift, I wouldnt think the bottom end would let go.
 
tornado112 said:
I would suspect it jumped timing??? I always use the locktite and the 3/4 inch impact to lock the gear on the pump. I have torqd to cummins specs before and had nothing but trouble... If you wipped a lifter it will make a knocking sound as well. i cant explain the noise at the oil pan but.. the botom end of the cummins is pretty tough. If your not pulling 4 grand every shift, I wouldnt think the bottom end would let go.
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How could I check the lifters? All the push rods came out straight and good
 
ending up being a stuck wrist pin, anyone else have this happen. everyone around here has told me it was caused by running 4k springs and not having the crank/rods balanced? whats your all's thoughts?
 
TRUBBS said:
ending up being a stuck wrist pin, anyone else have this happen. everyone around here has told me it was caused by running 4k springs and not having the crank/rods balanced? whats your all's thoughts?
Click to expand...

I think you're unlucky, because that is not a common failure.

Since each wrist pin is oiled individually from a separate oil jet/squirter in the block, I would check the squirter that sprays under the piston with the messed up wrist pin and see if it is plugged up. A bad oil filter that comes apart can send large enough debris through the oiling system to plug up the jets. Usually the piston melts before the wrist pin galls up and spins the bearing/bushing in the rod. The oil jet/squirter also acts as a cooling jet for the piston and that's why a plugged up jet usually leads to a melted piston before a "lack of lubrication" failure that you described in your last post.

And I'm 99% certain your 4k springs had nothing to do with the failure.
 
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