What was found
AIRCRAFT 10 MILES FROM AIRPORT, TRAINING FLIGHT, PRACTICING FLIGHT MANEUVERS. SMELLED SOMETHING WRONG, SCANNED ENGINE GAUGES. NO OIL PRESSURE, BUT OIL TEMPERATURE WAS IN THE GREEN. DECIDED TO RETURN TO THE AIRPORT AND LANDED UNEVENTFULLY. POST FLIGHT INSPECTION - OIL COVERING THE BELLY, WING ROOT AREA, INSIDE THE COCKPIT ON THE FIREWALL, FRONT CARPET, PILOT'S SHOES. NO OIL SHOWING ON DIPSTICK. REMOVED COWLING. LEAK APPEARED TO ORIGINATE AT THE OIL COOLER. REMOVED OIL COOLER (MOUNTED TO FIREWALL) AND PRESSURE CHECKED. FOUND CRACK (APPROX 1 INCH LONG) IN END CAP, ALONG THE MIDDLE OF THE BEND RADIUS.