how to identify oil cooler leak?

[GREASE FIRE]

i have a slow oil leak but i don't know exactly where it is coming from. First of all, it does not leak while the truck is parked since there is never any oil on the driveway. If it was an oil cooler leak would it leak while parked or only when running?
Also, i have seen some oil drip down the oil filter and since the cooler is right there i am wondering if that is where it came from. The cooler itself does not look too bad - there is some oil on it but there is also some oil above it as well so i don't know where it came from. After about 1000 miles since the last oil change i have not had to add any.

any thoughts?

thanks,
paul

 

[HammerDown]

First thing, make sure your oil filter is snugged properly. Next is to see if maybe the head or valve gasket is weaping.
After 20 years w/180,000 when my oil cooler started to weap it only did it in the winter when the o-rings shrunk from the cold. It didn't leak when the engine was hot.
As time went on (maybe a year) it would then leave a quarter size mark on the parking spot. Several months later it would leak when running hot, not bad but enough to make me crazy...then I did the repair. The o-rings were very brittle when taken apart however the oil cooler was very clean inside, no crud etc.
The front header was the leaker but now it's bone dry.