Engine Noise.. - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 12 (permalink) Old 06-05-2012, 06:17 AM Thread Starter
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Engine Noise..

I have an 05 2.2 Ecotec Cobalt giving me some trouble. It is my girlfriends car and she noticed some weird knocking noise about a week ago when the AC was turned on. A day later the noise was knocking without the AC on. It is coming from the passenger side of the motor and I have replaced the timing tensioner and took the belt off of the AC to see if that was it and I still have to same noise. When we had the valve cover off everything seemed to be in working order and no damage or wear. The oil was a little over a quart low when I first started looking at it and I did change to oil to see if anything was out of the ordinary but everything fine and nothing unusual about the oil. The knock is NOT a consistent tap tap tap tap. Whenever I start the car it usually does not start making noise until it idles down the whole way. When ever i rev it up it either gets quieter or goes away completely. When the AC is on at idle it gets worse due to the extra drag on the motor. I am fairly stumped on this one and the next idea I have is possibly the water pump. I am hoping to either fix it or quiet it up enough to trade in because last summer I believe I replaced every damn suspension component on this car. Anyways... anyone have any insight?
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post #2 of 12 (permalink) Old 06-05-2012, 08:43 AM
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Timing chain tensioner maybe.

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post #3 of 12 (permalink) Old 06-05-2012, 09:16 AM Thread Starter
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We replaced the tensioner. It's a little better than what it was. I am not sure if the chain strectched or a guide somewhere is broken.
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post #4 of 12 (permalink) Old 06-05-2012, 11:32 AM
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Well if the noise is like a chatter it's probably your timing chain hitting the guard.

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post #5 of 12 (permalink) Old 06-05-2012, 12:51 PM
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sounds timing chain related to me. If your serious about trading it in try putting in a thicker oil to try to quiet it down. Then trade it on a camaro ss

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post #6 of 12 (permalink) Old 06-05-2012, 06:46 PM Thread Starter
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Well, I tore the valve cover off and double checked the timing chain after running it. Timing chain is in good shape and there was no slack. Decided to tear the timing cover off of the side of the motor to check the balance shaft chain. Got it all off and the balance shaft chain has some considerable play in it. Going to order a new tensioner to see if that is the culprit. Also, there was some rubber coming off of the crankshaft gear. I doubt that was causing all of the noise but not sure what to do about that. Don't really want to tear that apart if I dont have too. Just want to quiet it up to trade in! I would love to get an SS Camaro lol I drove a 2012 six speed about a month ago.. had to sit in the car for a couple minutes afterwards to let my chubby go down haha anyways.. ill keep posting my trials and tribulations lol
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post #7 of 12 (permalink) Old 06-05-2012, 07:31 PM
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Wait now did you just write rubber from the crankshaft sprocket. That rubber is the damping material between sprocket and crank. That should not be coming apart and that might be your noise if that sprocket isn't turning true.

---------- Post added at 11:31 PM ---------- Previous post was at 11:14 PM ----------

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post #8 of 12 (permalink) Old 06-05-2012, 07:39 PM Thread Starter
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Its not rubber in between the sprocket and crank. I would be a little more concerned if it was that. There is a rubber ring on the outside of the sprocket.. really shouldn't be doing anything besides dampening it. I realize this could be part of the problem but we are going to try the balance shaft tensioner first since there is some noticeable play. The noise occurs at idle, which would be because there is not enough tension and oil pressure. The noise also occurs if you rev it up and let off the gas abruptly and sounds like a chain grinding/slapping at a higher speed. This too would be caused when you do a quick let off of the gas dropping the oil pressure and tension. I am really hoping this is it. More than likely if it was a lifter/rod bearing/ anything of that sort it would either get louder or quicker with the RPM's which this doesn't as it goes away. I appreciate everyone's insight. We'll see if my local part store can get the part in tomorrow and I'll keep everyone updated. I am hoping to have this thing fixed and GONE by the weekend lol
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post #9 of 12 (permalink) Old 06-05-2012, 07:45 PM
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That rubber goes right through the sprocket doesn't it? Isn't the balance shaft a spring loaded tensionner?

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Last edited by Coby7; 06-05-2012 at 08:27 PM.
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post #10 of 12 (permalink) Old 06-06-2012, 06:41 AM Thread Starter
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The rubber on the sprocket/gear whatever you want to call it is on the outer edge and does not appear to be something that goes through the sprocket. This is the very bottom sprocket on the timing system not the sprocket on the balance chain system. Almost looks like a ring around the teeth so the chain does not come off. However, the chain should just stay in place by the teeth. That's why im figuring it is just a dampener. As far as the tensioner.. I am not sure if it is spring loaded. I ordered the part and the description says hydraulic.
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