Knocking/Valve Train Noise - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
Problems and Service Talk about any mechanical problems you are having

 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 12-17-2015, 11:22 AM Thread Starter
Newcomer
 
Join Date: Dec 2015
Posts: 5
Knocking/Valve Train Noise

Howdy everyone,
My friend's 2007 Cobalt A/T recently began making what she described as a loud growl from the engine while she was out for a drive. While attempting to limp the car home, it apparently would stall at idle.

I took a look at it in the hopes it was something simple like a bad serpentine belt or seizing accessory pulley, but that whole assembly appears fine, although the serp belt is a bit worn.

The noise is a loud knocking from the cylinder head area that increases in pitch/intensity with engine rpm, and appears to be coming from every cylinder.

To me, it sounds like the timing is REALLY off and the engine is knocking. Engine had oil, and no idiot lights on. Going to run codes tonight, but in the mean time I thought I would ask the experts here what they think it might be.

Thanks in advance
Drumbalt is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 12-17-2015, 11:52 AM
Super Moderator
YourCobalt.com Premium Member


 
Coby7's Avatar
 
Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
Posts: 11,820
Garage
How is the coolant level? Sounds like she spun a connecting rod bearing.

Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

Never drive faster than your guardian angel can fly
Coby7 is offline  
post #3 of 8 (permalink) Old 12-17-2015, 12:01 PM Thread Starter
Newcomer
 
Join Date: Dec 2015
Posts: 5
Thanks for the response. Coolant level was fine, and not milky or oily. No obvious coolant or metal in the oil either.

Any other tests for bearing problems?

The noise was more of a rolling knock and seemed to be loudest at the spark plug, which made me suspect a timing issue.

I see no readily visible timing marks or obvious cam angle sensors - is there a way to check timing on this engine using a light? I think it's the 2.2.

Apologies, I'm used to working on older cars with distributor ignition. My wheelhouse is really 80's Volvo and Toyota 4 cylinders.
Drumbalt is offline  
 
post #4 of 8 (permalink) Old 12-17-2015, 12:09 PM
Super Moderator
YourCobalt.com Premium Member


 
Coby7's Avatar
 
Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
Posts: 11,820
Garage
To check timing you have to remove the valve cover and look at the marks on the chain and cam sprockets to make sure they align. The 07 came with a weak timing chain tensioner. Everybody I know with these I warn to upgrade to the "B" version tensioner, pay a bit now or pay much more later.


Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

Never drive faster than your guardian angel can fly
Coby7 is offline  
post #5 of 8 (permalink) Old 12-17-2015, 12:25 PM Thread Starter
Newcomer
 
Join Date: Dec 2015
Posts: 5
Cool. That would be with the engine at TDC I'm guessing.

My fear is that the tensioner has failed and the chain has skipped just enough teeth that the engine will run, but detonate.

I will run error codes tonight to rule out a bad knock sensor. Thanks again.
Drumbalt is offline  
post #6 of 8 (permalink) Old 12-17-2015, 12:54 PM
Super Moderator
YourCobalt.com Premium Member


 
Coby7's Avatar
 
Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
Posts: 11,820
Garage
It can jump one tooth without damaging the valves and still run. But 2 is a disaster.

Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

Never drive faster than your guardian angel can fly
Coby7 is offline  
post #7 of 8 (permalink) Old 01-04-2016, 10:58 AM Thread Starter
Newcomer
 
Join Date: Dec 2015
Posts: 5
Ran codes on the engine and got a P0326 - knock sensor.

Could a failed knock sensor cause the engine to retard timing enough to cause knocking, or is this code a symptom of a huge mechanical problem?

I'm hoping this is just a bad sensor. Where do I go from here?
Drumbalt is offline  
post #8 of 8 (permalink) Old 01-18-2016, 03:47 PM Thread Starter
Newcomer
 
Join Date: Dec 2015
Posts: 5
Update - replaced knock sensor, no joy.

Removed valve cover, inspected chain, no obvious damage, but some wear on the side of the chain. Removed and inspected the tensioner, cleaned it and replaced it.

Did a compression test to see if valves were bent, had good numbers (all above 190).

Engine still knock-y.

Anyone have ANY ideas on how to proceed? I don't want to just buy a used engine to drop in unless I have to.
Drumbalt is offline  
Sponsored Links
Advertisement
 
Closed Thread

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome