2001 Oldsmobile Alero Engine knocking

Tiny
AARONLU
  • MEMBER
  • 2001 OLDSMOBILE ALERO
  • 3.4L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 142,317 MILES
I have a 01 olds sleep 3.4. I had a head gasket leak I replaced gasket heliocoiled all 12 rocker arm bolts put it back together. Runs fine until it gets to operating temp. No tick. It's a knock from the engine. I can't tell if it's a piston a rod or it's the head. I didn't have it machines but I am a machinist and I checked it and it wasn't even a.01 out of tolerance. So what could it be? It's not a constant knock it's spatatic but sounds like a guy with a hammer in there. Oil flow is fine
Tuesday, October 6th, 2015 AT 3:51 PM

4 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Short cylinders out one at a time to see if you can find out what cylinder it is. Then check oil pressure with a manual gauge. If engine ran without noise it may be something in cylinder which if small enough you may be able to remove a plug start motor and it will get blown out, especially if it seems to be going from one side to the other. Other than that have a local guy look at it. A we can't give a good diagnosis as we can't hear it.
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Wednesday, October 7th, 2015 AT 7:13 AM
Tiny
AARONLU
  • MEMBER
  • 3 POSTS
What does a bent valve sound like? Would the car run? Would you hear a tick instead of a knock? I've narrowed it down to timing chain or bent valve. Thank you for your info. Helpful
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Thursday, October 8th, 2015 AT 9:46 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If it were a bent valve you may not hear anything at all except the predominant miss. If this is the 3.4L engine the timing chain has a tensioner so you wouldn't hear that. A piston would knock when cold unless it has a lot of clearance. Do what I said in first reply. It's a lot easier to get the CORRECT diagnosis.
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Thursday, October 8th, 2015 AT 11:59 AM
Tiny
AARONLU
  • MEMBER
  • 3 POSTS
Ok thank you very much for the advice
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Thursday, October 8th, 2015 AT 7:55 PM

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