Engine Knock

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  #1  
Old 12-11-10, 05:23 PM
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Engine Knock

I just helped my son in law replace the intake gasket on a 1997 Chevy 1500 Pick up truck ( it was leaking coolant ) 5.7 Motor 180,000 miles. After it was done . We started it up and it had a knock. We shut it off, and he called a friend to look at it and he thought that it was the lifters. We pulled the valve covers and only one lifter is getting oil. His gauge shows oil presure and we pulled the oil filter off and it was full of oil. The knock sounds louder than lifters to me. Anyone have any ideas? Any help would be appreciated.
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  #2  
Old 12-11-10, 06:49 PM
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You may be getting pressure to the sending unit, but it is possible that pressure is not realized from the oil pump to the valve train. Possibly bad oil pump, occluded line from pump. With only one valve getting oil, I'd say oil pump, and the noise could possibly be a crank shaft noise without oil, or the oil pump being hit by the crankshaft.
 
  #3  
Old 12-12-10, 12:19 AM
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Do you think it was just bad luck or something we did wrong?
 
  #4  
Old 12-12-10, 03:38 AM
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I don't know how far you got into the engine, nor whether or not you left a ratchet in the engine. It's been done. I think your next action should be to drop the oil pan to see #1 if your favorite ratchet is there, and to check the condition of the oil pump and its connections. With just the intake off, I'm not sure what you could have done to cause the problem.
 
  #5  
Old 12-12-10, 05:30 AM
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All we took off was the intake manifold so we could replace the gasket do to a coolant leak. also changed plugs,cap and rotor,wires, changed the oil and filter.
 
  #6  
Old 12-12-10, 09:24 AM
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Aha, more information is always good. I know you did the wires one for one, but go back and double check their position from the #1 on distributor. Any one misplaced could cause a premature or delayed ignition, which will sound as a knock and reduce performance.
 
  #7  
Old 12-12-10, 11:52 AM
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ok we went and got an oil primer tool and pulled the distributor, We ran the tool and never got any oil up to the top of the motor. It said it should pump oil to the mains and the valve train but nothing came out on top. I would of thought that the lifters supply oil to the rocker arms, and with out the engine running they couldn't pump oil. turned the ignition on while we ran the oil primer and it showed 80# oil pressure. Son in law wants to change oil pump but I would like to make sure if at all possible that that's the problem.
 
  #8  
Old 12-14-10, 07:58 AM
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knock

You didnt drop something in an intake port that is now on top of a piston did you?
 
  #9  
Old 12-14-10, 01:41 PM
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Thats exactly what happened. It was a distributer cap screw. My son in law and two friends pulled the heads and there it was. It was imbedded in the piston a little and the head was broken off of it, but the cylinder wall wasn't scored and the valve was good. ( got lucky ). So tonite they're going to put it back together, and hopefully it will be okay. Thanks for all the suggestions, and I'll let you know how it turns out.
 
  #10  
Old 12-14-10, 02:25 PM
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if the screw was within say 3/8" or so from the edge of the piston, it may have deformed the piston enough to cause a stuck piston ring.

just a little word for thought
 
  #11  
Old 12-19-10, 05:07 AM
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If the noise was not there before pulling the intake, then there is a good chance something metallic fell into an intake port while the intake was off. If the knock sounds heavy, like hitting an iron plate with a hammer, then you probably now have something lodged in the top of a piston. Question is, what cylinder has this foreign object in it.
 
  #12  
Old 12-19-10, 08:29 AM
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They already figured that there was a screw in it. They even figured out what piston it was. All the answers are in the replies.
 
  #13  
Old 12-19-10, 08:40 AM
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Yes....A screw in a combustion chamber will cause one HELLUVA racket, But......

WILL NOT EXPLAIN "DRY" LIFTERS!!!!!!......

You may not be out of the water just yet.
 
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