OE Report: Oil Leak at Base of TSIO-360-MB Oil Cooler

[pkellercfii]

As discussed in the engine monitors board, here, I spent last summer doing an owner-assisted annual which featured replacement of an old JPI EDM-800 with an EDM-900. After we thought we were done & ready to fly, in performing the post-maintenance engine runs we ran into a nasty oil leak from the base of the oil cooler. The oil cooler had been removed during this annual to facilitate the replacement of the OEM oil temperature sender with the JPI oil temperature probe.

It turned out that the oil leak was the result of a change to the oil cooler gasket. That change took place sometime between when the engine was overhauled, in 2009-2010, and now. Continental made the gasket thinner. In the attached picture, the old gasket, the all-red, slightly torn up gasket on the left, is shown alongside a new gasket, and a dime for size & thickness reference. For most of the oil cooler attachment screws, the thinner gasket isn't a problem. Eight of the nine screw holes which secure the oil cooler to the engine crankcase are through holes with no bottoms for the oil cooler screws to bottom out on. The middle bottom screw hole, though, is different--it does have a bottom. As a result, the machine screw at that location was bottoming out in the hole, rather than on the oil cooler's base attachment flange. That created our oil leak. Our solution was to replace the single thin washer called for in the Continental IPC with two thick washers. That still left about seven or eight threads in the screw engaged in the crankcase fitting that the oil cooler is attached to. It also corrected the oil leak problem.

Nasty "gocha" which someone pulling any bolt-on, gasketed oil cooler might want to know about.

--Paul Keller
89K @ KTTA