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Discussion Starter #1 (Edited)
Hello everyone. Hopefully this is the correct place for this. If not please let me know.

I have a 2009 Cobalt LS XFE with 147,560 miles. I bought it about 5 years ago with 72,000 miles and have always performed routine maintenance (oil change every 3,000 miles, spark plugs, air filters, etc, etc). Once it got to 146,000, I knew it would be a good idea to get the timing chain, water pump, guides, balance chain, etc, replaced. I got a kit off of Amazon (it wasn't a Cloyes unfortunately) but I made sure I bought a new ACDelco timing chain tensioner (the dome type one) for it. I took it to a family friend, who is a retired mechanic to do the work.

The issue I have though is that after having all that replaced, my timing chain now rattles on startup. It only lasts 1-2 seconds and then instantly the sound stops. I have a video of it here: https://youtu.be/hrMnCITa9tQ. It's driving me nuts trying to figure this out, as I love this car and want it to last as long as possible. The mechanic that did the work can't figure it out, so I've asked every other mechanic in my area (there are about 3 of them) to take a look, and each one has told me "That's normal for these Ecotec engines. Don't worry about it unless it starts doing it while driving it."

Anyone here ever experience this? I see a bunch of other threads where people get the noise BEFORE replacement, and changing to the new style tensioner fixes it. I unfortunately had the opposite happen. Never had any startup noise whatsoever and now after replacement I have the rattle on startup.

Any thoughts on what this could be? Bad tensioner? Installed wrong? VVT actuators? I would think if it was installed incorrectly I would have other issues. It has no check engine light, no rough idle, no other problems. It runs just as well as the day I bought it, it just has the rattle on startup. Any help or thoughts would be greatly appreciated!
 

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That start up noise is definitely a timing chain noise. If the install was done correctly then my guess is the tensioner is faulty.
 

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did you use the gm timing chain kit with a new tensioner,guides,chains and all that. a non locking vvt actuator can cause that issue as well.
 

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Discussion Starter #4
I was thinking it was the tensioner as well, but I've noticed that it does it even when the car has only been sitting for 5 minutes. That leads me the believe that it might be the VVT actuator(s), as I've seen a TSB floating around that says the cam phasers aren't parking correctly.

It wasn't a GM kit unfortunately, and it was a few different brands that I bought items from. It was an OEM style tensioner though. When he replaced the actuators, I made sure he had new camshaft bolts to use, which he did.

The only thing I haven't replaced are the VVT solenoids. I could be going crazy but it looks like there might be oil seeping out from them. It's very black/oily around them. I ordered new solenoids to put in to see if that helps at all (maybe they're keeping the actuators from parking correctly?) I'm doubtful that this is the case, but I guess it's worth a shot.
 

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Now when you say replaced the actuators you mean just replaced the bolts right? Or do you mean replaced the actual actuators themselves? The bolts are torque to yield and require replacement anyhow. The piece together kit scares me a little lol but if you used proper parts it should be ok. I always manually release the tensioner first before install so i know its ready to go. The oil leaking through the solenoids is a problem and definitely needs to be addressed since they control the actuators movements however they do not control the home lock position - that is controlled from the mechanical aspect of the actuator. I check the actuators by putting a 24mm or 22mm (i never remember) wrench on the cams and move them. If the actuator moves with the camshaft then its locked but if you move the cam and the actuator doesn't move then its bad and needs to be replaced.
 

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Discussion Starter #6
Thanks for the reply! I actually had the mechanic replace the actuators themselves (along with new torque to yield bolts). I thought if I was going to do it, do it right and replace everything. Last week I replaced the solenoids as well, but it didn't change anything. Doesn't look like they're leaking anymore though. I was hopeful though because with the old exhaust solenoid you could feel something moving inside if you moved it back and forth (which I don't think is right, but I could be wrong lol). As a side note, screens on both were clear and there was no sludge.

Thank you for talking about the tensioner as well. I thought that he maybe didn't install it correctly, but according to him, he did it just as you said (extended it first). I've seen a fair amount of arguing on how to actually install them so I wasn't sure.

As of right now it isn't getting worse, but isn't getting better. Still only at startup (although it is every startup, not just cold) for 2-3 seconds, with no check engine lights, and runs great. Right now I plan on saving up and hopefully within the next month get an actual shop to just completly re-do it. Lesson learned unfortunately.
 

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Discussion Starter #8
Unfortunately the mechanic that did the work trashed the old parts. I was kind of upset with that as I asked him to keep them. I usually keep old parts I swap out for a little while (especially if it's routine maintenance and nothing is wrong with the old ones) to make sure everything is good.

I'd really love to just be able to go in and take a look at everything myself, but I unfortunately don't have the space, tools, or time. I also don't trust myself to not screw something up with the timing lol. I can do smaller repair items, but I stay away from doing anything inside the engine.

I have an appointment Thursday morning with a garage who is willing to take a crack at it. I appreciate the help and suggestions. I hope they'll be able to fix it, and I'll be sure to add to the post what they needed to do/what was wrong. Otherwise I guess I'll be back with more questions lol.
 

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Discussion Starter #9
I figured I'd update since it's been awhile since my last one. I took it to the shop and they actually didn't fix anything. What they told me was that to them, they think it's the cam phasers bleeding oil out when the engine is shut off, rather than the timing chain tensioner.

Now, what they told me was to not worry about it. As long as it doesn't start doing it all the time, or starts lasting longer than 10-15 seconds, it should be fine. This is the 3rd garage that has told me this.

Talking to the mechanic that took a look at it (who they told me was also their head mechanic) he said he can't see any long term engine damage occuring with this issue, and told me just to run it and not worry about it. He said he's had Cobalts with the genuine cam phasers come in to the shop with the rattle for years for regular maintenance and the owners never had an engine issue because of it. Still makes me a bit nervous, but I guess if 3 different shops tell me not to worry unless it gets worse, I should take their advice lol.

So I guess overall I'm just going to drive it like normal and keep an eye on the noise. Hopefully soon I'll have some extra money and just get it done properly. Thanks again for the help and suggestions. If you have any other advice, feel free to share. Yes I have also learned my lesson which is to always use genuine GM parts and not random shit on ebay lol.
 

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Thanks for updating us on your situation. I agree with the mechanics and just keep an eye on it and make sure the rattle doesn’t get any worse. I agree that if the rattle lasts less than 3 seconds it’s likely nothing to worry about.

My 2008 had a startup rattle when I acquired it at 24k miles. It didn’t do it every startup, probably around 25% of the cold starts resulted in the startup rattle. Somewhere around 110k miles it stopped rattling and it has 207k miles now. I’m not sure why it stopped rattling, I’m guessing something was interfering with the tensioner under certain conditions, possibly a sludge particle, carbon deposit, or metal shavings during the engine break in. Anyway, my point is I wouldn’t worry about a brief startup rattle. Fix it again when it’s convenient for you. Enjoy!
 
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