This past weekend I had the pleasure of sitting in 97 degrees heat in bumper to bumper traffic in NJ after running highway speeds for several hours. With the A/C on the gauge never even came close to the mark between the 80 and 120 lines, I'd guess it was 2/3rd of the way to that mark (is that mark supposed to be 100C???).

In any event, as soon as it got to that point you could hear the roar/whine of the fan any time the engine revved and the temps came right back down to about 80C. You can really hear that fan roar when it engages. There is no reason your car should ever come close to 120C, something is wrong with it and you need to find out what it is.

First, make sure your aux fan works. Mine didn't when I bought mine. I had to replace the motor-side of it. That failure alone won't cause overheating I don't think, but it, combined with a bad fan clutch would.

Speaking of fan clutches, the thing about them is that they will only work if the radiator is doing its job and shedding heat. Depending on how well your cooling system has been maintained you may have a plugged radiator.

Finally, your sense of the water pump being to blame may be correct but it is hard to diagnose without eliminating everything else. If the pump is original then, yes, they have been known to fail this way.

But whatever it is, find it and fix it and don't drive the car while it is spiking that high...these engines are virtually bullet-proof, but excessive overheating is the one bullet that can penetrate its armor.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz