On October 15, 1994, at 1020 Pacific daylight time, an experimental homebuilt Rey Avid Flyer, N827H, collided with a berm while attempting a precautionary landing in a field near Bakersfield, California. The precautionary landing was precipitated by the engine overheating during cruise. The aircraft was constructed, owned, and operated by the pilot. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation. The aircraft was destroyed in the collision sequence. The certificated private pilot and his one passenger sustained serious injuries. The flight originated from the Shafter, California, airport on the day of the accident about 0930 hours as a local area personal flight. In a verbal statement to Federal Aviation Administration (FAA) inspectors, the pilot reported that about 45 minutes into the flight the instruments which monitor the Rotax engines liquid cooling system began to show a rise in temperature and pressure. The pilot recalled that the temperature reached the upper red line limit and he did not feel that the aircraft would make it back to the airport. The pilot reduced throttle and set up for a precautionary landing in a field. The aircraft landed beyond a barbed wire fence and rolled about 300 feet before an unseen gully was encountered. The aircraft collided with the far side of the gully. The airframe and engine were examined by responding FAA inspectors. The engine water pump was found to have a loose fitting in the top of the pump. The vent line and fitting could be turned by single finger pressure. The worm drive hose clamp on the vent line exhibited evidence of corrosion and the water pump showed a trail of dirt, dust, and rust mixed with anti freeze from the top of the pump in the area of the vent line fitting.