09 Aveo: oil in coolant - not head gasket

My daughter has an 09 Aveo sedan with manual trans and 105 K in miles. She's had it since new.

On Friday after about 150 miles of driving, the car began to overheat. Thankfully, she had AAA Platinum and got it towed home.

The first thing I noticed after popping the hood was that there was what seemed like oil in the coolant recovery tank. I put my finger in there and when I pulled it out it was caked with a brownish paste (See photo).

On Monday, she had it towed to an established shop (decades in business) that we have used before. They did diagnosis work over the past two days and they are ruling out a head gasket and said they couldn't make it overheat.

The shop wants to keep working on it. The only thing significant statement they made to my daughter so far was a question -- did you accidentally pour oil in the radiator? (Of course not). That doesn't give me a lot of confidence. Is there something specific to the Aveo that they might be missing? What could this be?

Attachment 11048

Hi Aveodad,

Yes, the same thing happened to me with my 2009 Aveo. Oil scum in the coolant tank. There was no problem with the head gasket, and the car didn't overheat. It ran fine. But the engine oil cooler mounted behind the manifold catalytic converter was leaking oil into the coolant. Because the oil cooler is mounted so close to the hot catalytic converter, the various seals inside the unit bake and harden, and then oil is forced into the cooling system whenever the oil pressure exceeds the coolant pressure. The engine oil cooler was also visibly dripping oil onto the lower part of the manifold catalytic converter, so that made it even more obvious.

Although I am no mechanic I managed to replace it myself with the following parts from my GM dealer:
93186324 Oil Cooler
55353327 Inlet Pipe
55353330 Outlet Pipe
25194218 Pipe
55573805 Manifold Gasket (or equivalent)

RockAuto also sells all the parts you need, at cheaper than dealer.
Those parts totalled $270 Canadian. It took me about 5 hours to do. Someone posted a excellent step-by-step procedure for replacing the "Maniverter". If you follow his steps you can see what need to be done, then just add the removal and replacement of the engine oil cooler on top of that procedure. I am guessing that a decent mechanic should be able to do the job in 1/2 the time. However, because they will need to remove the manifold converter to get at the engine oil cooler, if they snap any of the 3 rusted studs that hold the catalytic converter to the flex pipe, it will cost you additional money for them to drill out the broken studs and replace them. That's why when I replaced my engine oil cooler, I also replaced the manifold catalytic converter with a new Walker one. And then you will need a new upstream oxygen sensor too. The costs started piling up for me. At the end of the job, the parts costs alone was closer to $1000 Canadian because of the new manifold catalytic converter and oxygen sensor.

Since I replaced the engine oil cooler several months ago, there is no longer oil scum in the coolant tank. So, in conclusion, you might want to ask your mechanic to give you an estimate to replace the engine oil cooler.

Deano

I have an update. Although the shop my daughter brought the car to has been in business for decades, I began to doubt if they truly get involved in heavy repairs. By Wednesday, they claimed that they were not able to do the level of diagnosis to say exactly the cause of the oil in the coolant problem. All they could confirm was that there was oil in the radiator. They said they think it might be a head gasket (a repair they price at $1900) or the motor (priced at $900). However, they don't really know and in order to find out they would bring the car to a Chevrolet dealer for a proper diagnosis. They claim that would cost $300 to $400. Today, they let us pick up the car and it got even weirder still, they did not want to charge for whatever (minimal) level of diagnostics they did.

Obviously, this is not the shop to use if we intend to get the 09 Aveo fixed.

Questions:
- Is there something specific to this Aveo that prevents a good independent repair shop from diagnosing a major engine problem? Does the fact that its a Korean made Chevy make it more difficult?

-My daughter doesn't really want to keep the car at this point, but is it worth paying a couple hundred $$ for a proper diagnosis?

Quote:

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Originally Posted by Deano

Hi Aveodad,

Yes, the same thing happened to me with my 2009 Aveo. Oil scum in the coolant tank. There was no problem with the head gasket, and the car didn't overheat. It ran fine. But the engine oil cooler mounted behind the manifold catalytic converter was leaking oil into the coolant. Because the oil cooler is mounted so close to the hot catalytic converter, the various seals inside the unit bake and harden, and then oil is forced into the cooling system whenever the oil pressure exceeds the coolant pressure. The engine oil cooler was also visibly dripping oil onto the lower part of the manifold catalytic converter, so that made it even more obvious.

Although I am no mechanic I managed to replace it myself with the following parts from my GM dealer:
93186324 Oil Cooler
55353327 Inlet Pipe
55353330 Outlet Pipe
25194218 Pipe
55573805 Manifold Gasket (or equivalent)

RockAuto also sells all the parts you need, at cheaper than dealer.
Those parts totalled $270 Canadian. It took me about 5 hours to do. Someone posted a excellent step-by-step procedure for replacing the "Maniverter". If you follow his steps you can see what need to be done, then just add the removal and replacement of the engine oil cooler on top of that procedure. I am guessing that a decent mechanic should be able to do the job in 1/2 the time. However, because they will need to remove the manifold converter to get at the engine oil cooler, if they snap any of the 3 rusted studs that hold the catalytic converter to the flex pipe, it will cost you additional money for them to drill out the broken studs and replace them. That's why when I replaced my engine oil cooler, I also replaced the manifold catalytic converter with a new Walker one. And then you will need a new upstream oxygen sensor too. The costs started piling up for me. At the end of the job, the parts costs alone was closer to $1000 Canadian because of the new manifold catalytic converter and oxygen sensor.

Since I replaced the engine oil cooler several months ago, there is no longer oil scum in the coolant tank. So, in conclusion, you might want to ask your mechanic to give you an estimate to replace the engine oil cooler.

Deano

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I actually agree that the OP's oil cooler has failed; if the head gasket had truly failed, coolant would also be getting into the cylinder and burned while running; which would be noticeable as white smoke out of the exhaust. (and Thank you for the praise about my How to Guide for replacing the Maniverter; it pleases me to no end seeing people using it!)