Howdy, I have purchased a needs repaired HHR that was running hot, it has oil in the coolant system. I has no oil cooler and upon tear-down have found no specific source of the problem. Head gasket show no sign of being blown. Worried that the same problem will occur when I reassemble and contaminate everything that I have cleaned and replaced. Hoping someone has encountered this issue and can offer some advice or a solution. THANKS!!

 

Ran hot, oil in the coolant means that something failed. Since you didn't find the source of the problem, then just putting it back together and hoping..........well that's a gamble you'll probably lose.
At the least, the engine should be pulled, disassembled and checked by a machine shop. Warped head, cracked block between the cylinders are 2 possibilities.
Or you could find a used engine and do a swap out. That would be the easier way.

 

There is a chance that it is mixing at the water pump. While it is out that would be easy to check and change.