Cobalt Under Valve Cover Pictures

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I finally got around to replacing the timing chain tensioner on my 2007 Cobalt. I did this very same job on my 2005 about a year ago. The new tensioner fixes the start up rattle that both these cars were producing. It seems to be a known issue as GM redesigned the tensioner.
I wanted to share some pictures of the engine. It currently as around 140k on the clock. I have own it since it had 20k. Car is used pretty easy with mostly highway driving and few short trips. All but two of the oil changes have been synthetic oil. I use mostly what I get on sale and run the OLM down to 10-20% which equals to a bit 7.5 to 10k OCIs. What do you guys think?

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What do you think? Honestly I am surprised to see varnish on a car thats been using predominantly synthetic oil and your description of driving style. Other than that it looks good. A little varnish doesn't hurt much so its all good!
 
Originally Posted By: deven
What do you think? Honestly I am surprised to see varnish on a car thats been using predominantly synthetic oil and your description of driving style. Other than that it looks good. A little varnish doesn't hurt much so its all good!

Where do you see varnish? It looks fantastic!

Varnish:
http://www.bobistheoilguy.com/forums/ubb...ve_train_pictur

More Varnish:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1944999

Varnish starting to build into sludge:
http://crxcommunity.com/viewtopic.php?t=24872

The pictures posted look great, any varnish on the cover itself is completely trivial. Nothing wrong there.
 
The valve cover looks more like cooked oil to me,not actual varnish. If you look closely at the bare metal of the head there really isn't any. Only where there isn't much oil flow do we see what looks like baked on oil.
Is baked on oil considered varnish?
And synthetics certainly do varnish engines when the interval has run too long. We had pics posted her a few years ago iirc of a bimmer that used castrol,following the oil life monitor and everything inside was layered a reddish colour.
After doing more digging I found many more under valve cover pics of various European sedans with signicant deposits and all of them used castrol.
I'm not saying all engine that use castrol will have varnish. What I am saying is the only time I've seen it was with castrol. Not that I've seen that many as far as pics go,and none in person.
So yes it's possible. I've used castrol many times. Always a euro spec variety,and I've never seen any varnish however I don't run ridiculously long intervals either,so that might be the real issue in the pics I dug up on google.
Regardless. It's basically harmless. If it really bothers someone carb cleaner takes it right off,as do typical oil flush type products.
 
Tell me more about this timing chain rattle fix - I have a 2008 G5 (same as Cobalt) with the base 2.2 Ecotec. Thanks!
 
Originally Posted By: stevejones
Tell me more about this timing chain rattle fix - I have a 2008 G5 (same as Cobalt) with the base 2.2 Ecotec. Thanks!


I think GM redesigned the timing chain tensioner in 2009. Luke I said I've replaced both of my Cobalt's timing chain tensioners. A new one can be had from Amazon for about 30 bucks but be sure to but an AC delco brand. There are other manufacturers of the tensioner but I'm not sure they would be the new style. Very easy to replace but you have to remove the valve cover so you can tap the new tensioner which releases it from its compressed state. There are several how-to instructions on line at the various cobalt and HHR forums. I have read that if you have the start up rattle and do not change the tensioner it can cause damage to the timing chain.
 
It has a lot to do with the engine of course. Here is the rear bank on my 1MZ-FE after 299,000 miles, and this engine has seen nothing but high quality synthetics since its first oil change (and on a relatively short OCI). The front bank looks nothing like this, it is much cleaner.

Scroll down a bit for the cover pic:

http://www.bobistheoilguy.com/forums/ubb...nge#Post3397521

Originally Posted By: wemay
As for synthetics not leaving varnish? Yeah, ok.
 
Originally Posted By: tinmanSC
Originally Posted By: deven
What do you think? Honestly I am surprised to see varnish on a car thats been using predominantly synthetic oil and your description of driving style. Other than that it looks good. A little varnish doesn't hurt much so its all good!

Where do you see varnish? It looks fantastic!

Varnish:
http://www.bobistheoilguy.com/forums/ubb...ve_train_pictur

More Varnish:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1944999

Varnish starting to build into sludge:
http://crxcommunity.com/viewtopic.php?t=24872

The pictures posted look great, any varnish on the cover itself is completely trivial. Nothing wrong there.

I was talking about the varnish on the cover. I use varnish/discoloration interchangeably.
 
OP, try PYB next and see what kind of mileage the OLM allows. I'd be curious.*

The engine looks good to me. I agree on the bottom of the valve cover not being anything to worry about. Id imagine its just like the bottom of a filler cap. It isn't allowed to get as hot as everything else so it discolors a bit.
 
Last edited:
Originally Posted By: ltslimjim
Is there an average amount of months/time frame for the typical OCI it has?


Yeah, It seems that I change the oil in this car about every 8 to 10 months or so. It really varies and I generally just watch the OLM to know when it is time to change the oil.
 
Originally Posted By: dlundblad
OP, try PYB next and see what kind of mileage the OLM allows. I'd be curious.*



The type or brand of oil will not influence the OLM's function. O/P already stated the approximate mileage at which the OLM calls for a change.
 
Let's put the other way: Just 2 OCIs weren't with synthetic oils in 140k miles ...

Enough to cause the little varnish at the cover? Maybe.
 
Last edited:
synthetic = predominantly group III. what's the balance then?

If you really want to control varnish, you'd need to go group IV or V oils (predominantly).

Alternatively, 7.5k oci might be enough for your driving conditions?
 
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