Oil leak at oil cooler

[seo]

Hi. I have a '85 123 300D with turbo. The other day, after a highway speed drive, I noticed a little oil on the hood, right blowing back from hood/grille gap on the driver's side. Not even a teaspoon. I wiped it off and didn't think any more of it until the next time after I was driving on the highway, same thing again.
It appears to be coming from the oil cooler, which must have a tiny leak, and then the oil gets blown out through the gap when driving fast enough to create some air pressure in the engine comparment.
The leak is not apparent, even though I pressure-washed the oil cooler and then watched for a drip of oil to work itself out. Didn't happen.
I can take the radiator up to the radiator shop, and maybe they can repair it. Or I can take a radiator off a wreck I have.
Has anyone seen this kind of leak, have any ideas or good advice?
Thanks in advance.