09 Aveo: oil in coolant - not head gasket

[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