diagnosis please
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New User
Joined: Oct 2005
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diagnosis please
I am looking at an 86 f250 6.9 diesel auto. It has a slow knock at idle that speeds up as you accelerate. Any thoughts I have no idea. The truck is pretty solid and he is only asking 500. I can buy a runnin motor for another 500 is it worth it. How hard is it to change a diesel motor??
Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
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From: Ladner, British Columbia
The diesel motors are much heavier so your typical gasoline engine hoists probably won't do the job.
At the prices you mentioned you don't have a lot to loose if you are willing to take the risk on a used motor.
I would suggest you listen to a few other trucks of the same era. These diesel are loud with lots of knocking sounds, listening to similar trucks might confirm you concerns with regards to knocks you are hearing.
At the prices you mentioned you don't have a lot to loose if you are willing to take the risk on a used motor.
I would suggest you listen to a few other trucks of the same era. These diesel are loud with lots of knocking sounds, listening to similar trucks might confirm you concerns with regards to knocks you are hearing.
FTE Leadership Emeritus
Joined: May 2001
Posts: 13,653
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From: Cabot, Arkansas
Welcome to FTE and the diesel forums 89 f350 diesel.
Changing an engine is changing an engine. It's not easy, but if you have the knowhow then you have it. As Hamberger mentioned you will need a little bigger hoist than you normally would as you're looking at nearly 1,000 lbs of engine.
Changing an engine is changing an engine. It's not easy, but if you have the knowhow then you have it. As Hamberger mentioned you will need a little bigger hoist than you normally would as you're looking at nearly 1,000 lbs of engine.
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Its sounds like a wrist pin or maybe push rods. I can't really tell where its coming from. It is definitely not the normal diesel rattle. I have an 89 with a 7.3 and a buddy has an 86 with a 6.9 and it isn't normal.
Posting Guru
Joined: Sep 2002
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From: Northeastern Pa - USA
at idle and carefully,,, try loosening the injector of each cylinder (one at a time) and see if makes a difference in the sound. After you do that, try moving that injector to a different cylinder and see if the sound follows. If it follows, it is the injector, if it stays in that cylinder, its something internal. Might also be a lifter or bent push tube, which can be found by removing the valve covers. Once you find the difference in sounds, you'll know which valve cover to remove to further check.
