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Mike S.
Mike S., Chevy Mechanic
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Experience:  ASE Certified Master Technician
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2005 chevy aveo: coolant..head gasket or intake gasket leaks..piston

Customer Question

2005 chev aveo, coolant in oil. found bulletin 9294 ( or 10023757 ) concerning casting plug reseal, would like this bulletin or any info on this problem. the vehicle is not showing any of the issues related to head gasket or intake gasket leaks, plugs and piston tops look normal, no white or cleaning effect on them and no drivability or smoke out tail pipe issues. I did remove valve cover, full off white foam and coolant pooling around cam journals, pressure tested but could not see coolant leak this is the engine with the new pcv valve system .susect its related to this casting plug, or head gasket ( but how do I confirm - is head gaskets, or worse cracking seen on this vehicle ) . I suspect the casting plug is internal as external plugs would leak outside and not contaminate oil. thanks for any extra info beyond the bulletin you can provide.
Submitted: 6 years ago.
Category: Chevy
Expert:  Mike S. replied 6 years ago.

You said you pressure tested it. I assume you meant pressure testing the cooling system. Did the gauge hold pressure? Just because a head gasket leaks doesn't mean it leaks into the combustion chamber. It could only be a blown gasket between the coolant jacket and oil jacket.

I don't see that bulletin, do you have a copy of it or a link?

Expert:  Mike S. replied 6 years ago.

On this engine, I see a coolant hose connected to the throttle body, make sure that the coolant isn't entering the engine at that.


Customer: replied 6 years ago.

Hi, If the coolant was entering via the throttle body it would enter the cylinders and burn off giving smoke and cleaning the plugs and piston tops, this should also give a hard start, misfire or poor running condition, which is not evident, but. I have already peeked in the throttle body and no signs of staining or coolant when pressure tested. I don't see how the coolant would enter the oil pan this way unless its bypass from washing down the cylinders giving above conditions. I should mention the oil has about 2 liters of coolant in it since I changed it a week and half ago, this amount would definitely show out the tail pipe. The only way I see it entering directly into the oil pan is either a head gasket ( with out the usual signs in the chambers ) or a cracked head/block, are either of these a common issue with this engine? or am I missing another option, like the tsb I found, but it was only listed on the internet sites with a release date of early 2007.

Expert:  Mike S. replied 6 years ago.

I didn't find anything listed under tsb's for any cracks or even coolant in oil. I did find what you were talking about though,

2005 Chevrolet Aveo 1.6L MFI DOHC 4cyl vin 6.

L91 2003 to 2009 ENGINE,1.6L,MFI,DOHC 1.6-6(L91)


That is the correct RPO, L91 is the 1.6L MFI engine.

Give me a few minutes and let me see if I can find out how to replace that casting plug.


Expert:  Mike S. replied 6 years ago.

I cannot find anything on repair, only links to the tsb that say RESEAL CASTING PLUG. I don't have anything in my Chilton online and can only find the same tsb at the gov site.

Results : 1 | All records displayed

Make / Models : Model/Build Years :
CHEVROLET / AVEO 2004-2008

Service Bulletin Number : 4294 Date of Bulletin : DEC 01, 2007
NHTSA Item Number : 10023757

Mike S. and 3 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
Expert:  Mike S. replied 6 years ago.
You are welcome and thank you!

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