Hello, I am in the process of buying an ‘07 HHR with unknown mileage and unknown codes as the battery has been disconnected for some time. Once I restore power to the car again and try to get it running and succeed how fast and what codes should I look for to use as a guide to pinpoint that it does indeed have a blown head gasket. I know that on older cars You could sometimes tell due to milky oil, is that still the case? Also, on older front drive cars that had aluminum heads if You overheated the car just once You ran the risk of having a warped and/or cracked head. Are the Ecotecs a more forgiving engine? If the head is warped can it be saved by planing it down like You could on the older cars (within reason of course). I would like to try and save the motor in the car if possible because my daily driver now is going to need valve stem seals directly and I don’t want to be without a car. Thanks in advance for any help that anyone can give me. God Bless You All. Stay Safe and Healthy.

 

Depending on the temperature a warped head is possible, and bring a close tolerance engine, planing the head could allow the valves to kiss the pistons.
This isn’t common, usually the head is still flat and true , no real codes to point to a blown head gasket.
If you’re going to do this replace the head bolts and valve seals , there are kits available with all the parts you need

 

I would only pay what I think it is worth if it needs a new engine. That may be what you are looking at.

 

Milky oil is a sign of coolant in it so, yes a sign.
Might be cheaper to get a new head instead of valve guides. Quicker, anyway.
You are thinking of aluminum heads on iron blocks; Ecotecs have alloy blocks and alloy heads.
Check for rodents living in the air filter or chewing on wires.

 

Cylinder leak down test should reveal if the head gasket is bad.

 

Take a battery and a charger and read the codes.

 

Now don’t forget the codes will be cleared by the dead battery, so there probably isn’t going to be any codes to read.
Donbrew , should not need valve guides , just new valve guide seals.

 

I thought they were the same thing,

 

Valve guide seals, keeps oil from the valve stem to the valve guide

Valve guides, press into the head and the valve stem slides into them

 

How long has the car been sitting? Try to evaluate the condition of the oil. Is it low? If oil changes were neglected and then it sits for a long time, all sorts of things get gummed up. In addition to rings, valves, lifter, the chains, tensioners, and oil squirter, and if it's a 2.4, the VVT solenoid valves and phasers. Careful how you interpret compression and leakdowns if don't know for sure what's sticking.