Water pump whizzing??
Trending Topics
I don't know what you're describing as a whizzing sound, but you can isolate the WP bearing with a mechanic's stethoscope to see if that's indeed where the sound is coming from. Whizzing might be okay, grinding or clunking type sounds would not. If you have really odd mechanical noises coming from the WP it's possible the impeller is not properly fixed to the shaft and that would reduce cooling.
Before looking at other things, have you confirmed that it's simply not a bad reading (bad guage or bad sensor)?
I don't know if you have another thread running about what you've tried, so I'll kind of summarize and try to be very basic. There are two halves of the cooling system, the liquid and the air. The liquid draws the heat from the engine, and the air draws the heat from the liquid (through the radiator). Thus, you have to look at both halves of the equation whenever you have a cooling problem. First check to make sure your hoses are all sound and not leaking. Same with the cap and the remainder of the cooling system and you may need to pressure-test the system to find leaks, you can rent a pressure tester at some auto parts stores. Leaks are bad on two fronts: they not only let coolant escape, but they release pressure, which will lower the boiling point of the coolant dramatically. It can also induce cavitation and air pockets in the liquid side, both of which reduce the coolant's ability to draw heat from the engine and to shed it to the air passing through the radiator fins. Soft hoses (particularly on the intake side of the equation) can be sucked shut, decreasing coolant flow, with a host of negative consequences.
If that all checks out then a new thermostat and a proper flushing/back-flushing of the cooling system may be in order. Note that sometimes during a flushing the WP bearing will actually make noise, thus indicating it's need for replacement. After flushing, it's important to refill with the proper coolant in the proper proportion. Too high a percentage of coolant will both drop the boiling point and cause an increase in operating temperature.
That's pretty much the liquid side. On the air side, you would need to check for blocked or bent fins in the radiator or A/C condenser (since air has to pass through both). These are often mounted very close together and I've seen leaves and junk (even mice) stuck between the two, blocking off up to the bottom 1/4 of the radiator fins. Thus you may have to partially remove the radiator or condenser to make a thorough investigation. Some cars also have an air deflector mounted low to deflect air up through the radiator/condenser and you should check to make sure this is in place and not damaged, falling off, etc.
If the car has normal temp out on the open road, but runs too hot in town, the fan(s) or fan clutch should be checked.
If everything checks out and the operating temperature in normal conditions exceeds the typical temp for that brand and model, then it is possible there may be an obstruction in the liquid side of things, perhaps corrosion that has blocked a passage in the block or head, or clogged cooling tubes in the radiator. This is more likely if you have an older car that has not been properly maintained or one into which people have poured in lots of stop leak; many of those congeal in passageways and block or reduce coolant flow.
Lastly, if everything works properly but you're still not happy with the temp, an auxilary radiator (or a larger radiator) is the ultimate cure. Often you can have your old radiator re-cored with a larger core that will increase the capacity of both the liquid side as well as providing more cooling area for the air side.
Good luck and enjoy the ride,

Greg
The Best of Mercedes & AMG



