My kid came in, complaining about an oil leak that suddenly appeared under his 940T. We looked around to find the usual film of oil all over the bottom of the bellhousing and transmission pan and concluded: "turbo oil drain o-ring or rear seal". But which was it?

I had earlier bought from Keep-It-Cool (http://www.keep-it-kool.com/) a UV penlight for fluid leak detection. This cost $50 and I purchased it because of an a/c leak that we fixed by tightening a connector, found by looking for leaking oil. The penlight uses an LED to create a "pure" UV in the fluorescing range to maximize visibility. I also bought a $3.95 pair of UV-enhancing glasses at JCWhitney to make the lamp work better.

In the case of the engine oil leak, I found a bottle of $3.50 "oil dye" at NAPA. I power washed the underside of the car to remove the oil film and poured the dye into the oil fill. We ran the engine for about five minutes and I crawled underneath while wearing my UV glasses. I shined the penlight up and, sure enough, one could see the leak from the turbo drain bright as day: a glowing yellow. This device certainly saved me from doing a rear seal, since the pattern of the leak (blown around by fan air) sure looked like it was coming from the seal area. It wasn't.

The lamp works like a champ and I recommend it to anyone for finding fluid leaks. NAPA carries dyes for every fluid, making everything from power steering leaks to tranny problems easier to diagnose.