when ever i turn my keys to the on position, the water pump cylces and it sounds like marbles are rattling. is it the bearings or something in the timing cover. it only does this when the engine is off and the keys in the on position. it does this for about 2-3 seconds. i recently had the therrmo stat changed and it is running about 200-210 at night and it never got above 180 in the heat and traffic. i kind of think they put the stock stat in instead of the 160 i had before. what do u guys think?