I was just given a 96 CX with what they suspected was a blown head gasket; it has been sitting for quite a while, the coolant reservoir has what appears to be oil in it (it's black with oil-slick on the surface) I drove it 65 miles and it didn't appear to use any coolant that I could tell but will look again after it cools down overnight. My question was, before I tear into the engine I'd like to drain all coolant and run some kind of degreaser to flush any oil out of the radiator and block, anyone have any suggestions as to anything they've tried? Thank you in advance!

 

Don't waste your time. Oil in the coolant is diagnostic of a blown head gasket or cracked head.

 

Right; but My idea was to use the coolant system and water pump to run maybe Prestone 2 in 1 flush and degreaser (has anyone here used it?) to try to get rid of residual oil in the core, block and lines. I would then pull the head and send it off to be checked before I replace the head gasket and head if needed. Might just go ahead and replace the radiator too if it looks bad enough

 

In my opinion, you are putting the cart before the horse.

How many miles on the D16Y7 engine?

Drain the coolant and oil and inspect them. Remove valve cover and inspect the oil there.

Compression test the cylinders.

Check for CEL codes.

It's possible that the engine was severely overheated, which warped the engine. Remove head and use precision straightedge to check whether head and block mating surfaces are flat to spec. If there is substantial warping, you may want to look into a replacement engine.

Take head to a reputable machine shop. Tell shop about oil in the coolant. Shop will leak test head and inspect valves. If head is not cracked, shop can replace or regrind valves and resurface head.

Figure out what you are getting yourself into before you spend time and money cleaning some oil residue from the cooling system.

 

205k on engine
I was going to drain both anyway to see what all comes out, just pulling the dipstick the oil looks good, not milky
the CEL is not on; can I check an OBD I? do I need to jump a connection?
Thank you for your help! I appreciate it.

 

Yep, jump 2P service connector above ECU behind passenger kick panel and watch CEL blink codes.