I know there is a lot of threads about valve train noise and a lot misconceptions but i cant find one situation that is close to mine. When my car is warmed up it makes a loud almost knocking noise for a few seconds then bogs low and clears the noise. Vince at Trifecta said that my knock sensor is reading something but is most likely NOT rod knock. (Rod knock is typically heard when engine is cold). The noise doesnt happen on initial start up and i think it has something to do with oil pressure getting to the lash adjusters or roller followers or something on top of the motor because when i get in my car and start driving after its been warmed up it doesnt make the noise. Please let me know what you think. Thanks guys

 

Difficult to say, but I would suggest an updated timing chain tensioner if you have not changed that. available from CED not expensive and easy to replace. remove and put in new, u be good.

 

This. Sounds like the Timing Chain Tensioner is dying.

 

alright, so i got a tensioner and put it in and no dice i took a video of what im dealing with and heres the link: ‪Cobalt "knocking" noise‬‏ - YouTube

i dont really know where to go from here :/ i wanna take off the valve cover and run the car but i also dont wanna get sprayed with boiling oil. any suggestions will help, thanks guys

 

Take off the valve cover and inspect all your lifters/rockers, as well as the cam. Make sure the chain is tight... probably be worth making sure its timed correctly, as well... but if the issue is only there when the car warms up, then that shouldn't be the case. (If you DO check the timing... don't rely on the colored links, they aren't always correct.)

If all checks out well up top... you're probably going to need to drain the oil, drop the oil pan, and check the rod bearings.

 

yea i know its timed correctly cuz i got retimed back in the spring and its all good now. but yea im probably gonna check under the valve cover again. u think rod bearings could be the problem? ive heard it happen on a cold start every once in a while but not as nearly as loud and for less than a second. what would be wrong with the bearings for it to be making that terrible sound at operating temp, thanks man.

 

hard to tell for sure from the vid but it sounds like timing related to me. have you had the oil pan off this car? if so issue could be excess rtv stuck in oiling system.

 

Yea i took the oil pan off in winter to put the new one withali the return line bung. I don't think its timing cuz like USMC said it would be happening all the time :/

 

alright, well today i took off the valve cover and made a pretty interesting find... my cover for my VVT gear was cracked in half and just chilling there.


everything else seemed to look fine and no scratchy or dry spots or anything. When i started the car the noise was still there. me and my friend think it could be the rest of the plastic ******* around in the bottom of my timing area but cant see until i take off cover. any other suggestions? thanks guys

 

See........timing related

 

^^^lol if only that solved my problem. i think i still need to find that other half......... lol

 

wow that sucks for you. at least remove front cover and look for trash and correct damage if any. Its a pita job.

 

yea thats the plan, my buddy has a lift so it will ease the pain of the cramped space but its still cramped as hell in there. i'll keep u guys posted

 

Take the pan off. There's probably chunks/pieces in the bottom... don't want them clogging up your oil pick-up and starving your engine of oil.

 

think i should take off my pan or timing cover? or both? thanks

 

Answer to that question is already in here...

 

sorry i just like to make sure before going into a bigger project than a valve cover, ill keep u guys posted

 

alright so i got the the timing cover off and here is what i found. the chain is loose at only one part and looks like the tensioner that is supposed to tension isnt working properly. could that be that its not getting oil?

‪Loose timing part‬‏ - YouTube

 

thats the balance/waterpump chain. There is currently an issue with the chains and tensioners of the newest 2.4s but its very rare on the 2.2s there is a new tensioner, and the chain gets replaced. they actually make a noise similar to your noise, but is usually only does it with the ac on

 

Anything you suggest? Im also going to take off the oil pan tomorrow so ill let u know what I find

 

can you explain more? with my AC on it sounds like lifter noise almost...only with AC on though.

 

update:
took of my oil, everything looks perfectly normal and is clean. im thinking it is that loose part on my balance/waterpump chain. anyone know what the tensioner shown in the video is called so i can possibly replace it? thanks

 

Ecotec Water Pump Chain Tensioner 90537300 - Crate Engine Depot

Ecotec Timing Chain Tensioner Bolt 11588522 - Crate Engine Depot

This chain says its for the LSJ, but I was under the impression that this chain was the same across all... Maven would know for sure.
Chain LSJ Water Pump and Balance Shaft 90537370 - Crate Engine Depot

 

do u think i need all 3?

 

Doubt it. I don't think the bolt is TTY, so you should be able to use it again... but don't take my word for it. And if Maven says they replace the Tensioner and the chain... so I would suggest doing the same.