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crazyman03

Engine knock or transmission knock?

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I wanted to get some input on some engine "knock" that I'm experiencing. 

 

Vehicle: '01 Chevy S10, 2.2, Auto, RWD, 140k.

 

I have what I think is bottom end knock. Strait forward right? Rod bearings. The more I think about it I'm not too sure. The knocking I get is very faint at times. It doesn't speed up or slow down with RPM really at all. At one point a while ago, I had the hood open and the serpentine belt tensioner would rattle to the same pitch. I replaced the tensioner (the pulley was a bit wobbly) and the noise went away I thought. But you can still hear it faintly. The pulley does not rattle like it did anymore. 

 

When I do hear it though, It is when you are lazy on the throttle between gears then it goes away. From what I noticed though, It does not do it when you are just in park or Neutral. Also, when in motion (it seems) it does not occur if you throw it in neutral or even kill the engine while in motion. 

 

So what does that leave? 

 

One thought I had was Torque converter? I do have a code on the dash related to it. (I dont have the code though I just remember it was the torque converter).

 

Is there anything else I should check? I'd hate to pull the motor out and see that the rod bearings are alright. 

 

 

-Justin

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In my experience, when a rod bearing fails, it fails. The noise doesn't come and go. The higher the rpms, the louder the knock. Also in my experience, when a rod or main bearing fails, the engine only has a few miles left.

 

Could be the flex plate. Had a 63 Fairlane many years ago that the original owner replaced the 289 with a new one. Problem is whoever did the work did not torque the flex plate bolts. That noise did come and go. I initially thought rod bearing also but quickly decide it had to be something else. The Ffex plate was both loose and cracked. 

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Thats kind've what I thought. I had a V8 Grand Cherokee that I've done Rod bearings on because #8 spun. The noise was more of a rattle and was louder the faster the motor was. This doesn't sound like that. 

 

On a side note, i have to do head gasket on it because i'm leaking coolant out of there.. 

 

 

-Justin

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Does it do it when cold? Usually rod knock wont be there when the oil is cold as it is nice and thick. A flexplate wouldnt car about temperature. Rod knock as you know is a very sickening hollow noise and sounds the same on all engines. You can even feel rod knock by turning the engine by hand with the plugs out. If it is a flex plate you wont feel it by turning it by hand.

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Thought I'd rehash this post.

 

I did the rebuild, everything except the front/rear mains and timing chain. (though, why i didnt think to check it is beyond me at this point:-() 

 

I was rather forced into the rebuild when my headgasket was starting to spew out the side :-/

 

I still get a rattle. its pretty consistant with the serpentine belt tensioner rattling. Rev the motor up, the tensioner stops rattling. The tensioner and pulley are practicaly new. I replaced it last summer for the same problem. Now the problem is back. I'm thinking whatever is causing the rattling is chewing through the tensioner. ideas? 

 

could it be a warped pulley?? how would you go about checking them?

 

-Justin

 

edit: thought I'd share a picture or two

10850178_10155376943570727_8856148158176

 

10959322_10155378230365727_7454350275179

Edited by crazyman03

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I've seen bad tensioners right out of the box.

Did you replace the belt at the same time? Have you removed the belt and checked it for hard spots?

 

An off-center pulley could cause the belt to wobble, but you would be able to see that as the pulley spins.

 

Does it have the GM harmonic balancer, or does it have a solid crank pulley?

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I think it is a solid pulley (shown above), I removed the belt and ran it without and didnt hear the noise. When I pulled it, I looked at the belt.. It looked *okay*.. But i imagine it could be a hard spot in it not flexing..

 

 

-Justin

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Sometimes those balancers will go bad and the outer section moves about a half turn then re-wedges itself so the outer section isn't perfectly straight, and that causes the belt to deflect and yank the tensioner around.

 

With a solid pulley that can't happen, but I have seen the solid pulleys bent from people using jaw-type pullers on them.

 

 

Another odd thing I've seen is if the belt has ever had any oil or petroleum type cleaner spilled on it the rubber can expand and cause sort of a high spot, usually on the flat side of the belt. That causes the tensioner to move every time that high spot moves across one of the flat pulleys since it pulls the belt tighter.

 

If the tensioner feels pretty strong (like it should be able to hold the tension just fine) you might want to try a new belt if you haven't already. If the belt is new, spin all the pulleys by hand and see if you can see any of them wobble, especially the larger diameter ones like the WP and SP.

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