Coolant on top of engine near oil cooler

[Htci]

I found coolant on top of the engine near the oil cooler a week ago. I attempted to find the source but ended up just drying the fluid and monitoring the issue since the car was otherwise functional. No oil in coolant reservoir, no intermix detected on dipstick, no smoking exhaust. This area is near the intake manifold, head gasket, and oil cooler. If it were head gasket leak I’d expect intermix and smoke so I’m leaning towards oil cooler. What do the experts here think? Pictures coming in a few.

[Htci]

[JFP in PA]

Remove and pressure test the cooler, it looks like it has an external leak.

[rexcramer]

The oil cooler has two sets of o-rings. The water side of the oil cooler and or the o-rings could be failing.

Here is a picture of the bottom of an oil cooler; https://www.pelicanparts.com/catalog/SuperCat/1041/POR_1041_ENGOIL_pg6.htm#item20

[Htci]

Thanks Guys,

I'm looking at the following diagram for the o-ring part numbers and see more than two sets (total of four o-rings and that's likely due to the intermediate plate)... Also, after reading other posts related to oil cooler replacement I recall that some suggest an oil change. If I drain the coolant, bleed the coolant from cooler by removing breather tube, all of the coolant should leave the system so shouldn't I expect virtually no cross-contamination?

Please advise and thanks so much!

[JFP in PA]

You need to drain the cooling system before pull the cooler. This makes it a good time to do any cooling system updates like a low temp stat, water pump, or anything else that needs doing. And by the discoloration on the sides of the cooler, it may not be the o-rings that are leaking.

When pulling the cooler, slide a plastic bag under it when first lifting it, that prevents any residulal oil or coolant from getting into the wrong passages.

[Htci]

Update for anyone else with this issue. My process for resolving this issue consisted of draining about 2 gallons of coolant, Removing intake tube to allow for clearance when removing oil cooler, disconnecting the top tube, unscrewing 4 Allen screws, removing oil cooler with small pry bar (required very little force, allow a few seconds for remaining oil and coolant to drain from cooler, slide oil cooler rearward and into a plastic bag. A few ounces of oil and coolant were caught in the plastic bag and maybe an ounce spilled out into either of the passages; so little that I’m not worried about cross-contamination. Cleaned area including scraping small amount of o-ring residue from mating surfaces, Replaced 4 o-rings using part numbers 99970738940 and 99970740940; 2 of each. Reinstalled oil cooler using blue loctite on the 4 screws and hand tightened as not to strip threads. Refill and burp coolant system with the same coolant drained; no intermix in drained coolant and it had less than 10K miles on it.

Easy job. Hardest part was waiting a week for the o-rings. During last 100 miles I’ve inspected area and coolant reservoir and there is no longer coolant leak or any sign of intermix in reservoir.