I've seen a few noisy water pumps, no bad bearings, just a rubbery squeaky noise. Bleeder on thermostat leaks sometimes and you'll get the coolant crusty buildup. Thedon mentioned the roller rockers. It seems to be a mixed bag on those, they give lots of warning before causing serious damage though (valve tick). Just had 2 recently that had spark plugs so bad that the incomplete combustion burnt the exhaust valves. Spark plugs don't seem to make it to 100k like they say they should.