Is it a constant alarm or intermittent, like a beep every 2 seconds, or a different interval? Do you have a drive oil monitor? Have any modifications been made to the engine, like addition systems installed? When was the water pump last serviced? Have you tested the gauges to ensure they are at least giving a reasonable indication (did you ground the engine end of the sender wire and look for the gauge to 'peg' high?) When were the exhaust manifold and elbow last checked/changed/cleaned?
