oil in coolant but not in engine... thoughts?
 

so i picked up a boxster for a parts car a few weeks ago. the PO said that the engine blew a head gasket so sold it for cheap. the engine still ran but rough at best from what i recall. got the car home and began tearing down. first there were signs of oil in the cooling system. chocolate foam residue all over the reservoir and all throughout the cooling system hoses and radiator. but surprisingly no coolant to be found when i drained the pan. there was a bit of oil pooling around the top of the engine, left side only, so i suspect it might be some sort of leak/ failure from the oil cooler/ heat exchanger. right side of the engine is relatively oil free. from those observations alone, what preliminary rough conclusions can be drawn? no leakdown or compression check has been done. but i am thinking perhaps not a head gasket failure? thoughts, opinions... thanks.

Occam's razor says: the prior owner poured oil down the wrong fill tube into the coolant tank

According to the experts, head gasket failure is rare on these engines. More likely is a failed heat exchanger or rubber O rings where the exchanger seats to the block. Oil usually gets into the coolant more often because of the higher oil pressure forcing it into the coolant.
I would remove the exchanger and have it pressure tested & replace if required (or turf it for a new larger S exchanger). New O rings are cheap.
Use the search function for heat exchanger and see the dozens of failures - you may be lucky and have a good engine cheap ......

Steve is spot on; oil cooler failures while not common, do happen with these engines. Pull the cooler and have it pressure tested, a new one from a dealer is only about $200, but be sure to always use new O-rings.

If you end up needing an oil cooler, I have one in excellent to mint condition.

These engines do not blow head gaskets; the head gaskets are more robust than the heads and cylinders. These engines crack heads, especially if the car is a '00-01' S model.

We have had ONE bad heat exchanger/ oil cooler here ever. We have had dozens and dozens of cracked cylinder heads and cracked cylinders.

Most of the time we get intermixed engines from shops that have already changed the oil cooler and they wasted a ton of time cleaning the systems only to find out that the problem wasn't solved. When we have intermix I jump straight to a cracked head as my hypothesis and I have been right in 99% of the occasions. This saved time, money and frustration by just sucking it up and taking the plunge. Taking the plunge requires confidence which is gained from lots of prior pain and suffering.

will a leakdown test give me more information about the possibility of a cracked sleeve or cylinder? i'd like to determine whether or not the engine is okay to keep as a spare or if it bad enough that i can start taking it apart to learn more about them.

for clarification though, a cracked cylinder will not necessarily leak coolant into the engine?