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Engine Knock, Can't Find Where

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Old 01-05-2019, 02:00 AM
Dpavel2006
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Engine Knock, Can't Find Where

2000 Ford Econoline E350 with the 5.4. 147k miles.

Bought it, had a slight knock (two knocks) at startup. Figured it needed an oil change, bad fram filter. Drove it 10 miles home no issues.

Next day drove about 30 miles, starts knocking at random rpms. Would stop if I changed the rpm, more gas or less gas. Had a bad serpentine belt. Swapped out the belt and drove some more. About 30 more miles, knock gets loud. On start up, and idle and at most rpms. Got it towed home.

Spend the following day trying to figure it out. Pulled plug wires, knock didn't change. Drained the oil, no metal, went through it with a strong magnet and didn't find a single piece of metal. Oil had a little bit of a milky color, but coolant didn't seem to have oil in it, a bit of white smoke on startup but goes away after a minute or two.

Tried pin pointing where it's coming from but can't figure it out. It drives great, like it has no issues. No engine code/light.

Possibilites: cracked/loose flexplate
Broken exhaust stud/cracked manifold
Loose spark plug?
Spun bearing?

Not sure how to keep checking. Not trying to drop the oil pan, any other things I should try before? It sounds like a loud rod knock but doesn't "feel" like it. I don't feel a vibration and I drove for a while and didn't throw a rod. While driving, at certain rpms it goes away. I drove it to a mechanic, and at 45mph, flat ground it was silent, but up hill, or letting off the gas it knocked. Oil level was good when I got the truck and I filled it up with fresh oil, which made no difference.
 
  #2  
Old 01-05-2019, 02:50 AM
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Sam I Am
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Take the belt back off and check the water pump for play, and all the other pulleys, idler, & tensioner.
You can even run it BRIEFLY with the belt off to see if it is a belt driven accessory.
 
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Old 01-05-2019, 11:08 AM
alloro
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Watch the belt tensioner as the engine is running. Does it hold steady or does it bounce?
 


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