1978 volvo penta 280A. Took oil cooler off to take a look inside, found a little debri on the water intake side so blew compressed air thru to clean out and afterwards found some oil residue (not much) coming out the water outlet side. Does this mean the cooler is going bad? I wouldn't think any oil residue would be where the water flows thru but I'm not exactly sure how these work. Did not have any problems with engine, just trying to do preventive maintance right now. How can you check an oil cooler? Thank you!
