Expert: Mike Evans - 6/28/2009

Question
96 Merc Sable Duratec DOHC

In the past I had a water pump leak. I changed the serpentine belt and no problem for 2 years.

Now small leak of Antifreeze from pump shaft. The leaking fluid is syrup like. I changed belt again and hardly any leak to speak of (1 cup in 500 miles).

Q Is there a product that seals the water pump shaft but doesn't clog the radiator? If so what is it?

Thanks in advance.

Answer
    The only way to seal a water pump leak is to replace the water pump.  The problem is that once the leak becomes apparent on the outside, the coolant has washed all of the grease out of the water pump's shaft bearings.  So, even if you could get the seal to swell up and reseal (temporarily, it is going to continue to wear), the unlubricated shaft is going to wear out pretty fast.  Remember, the water pump shaft turns at the same speed, more or less, as the crankshaft.  It takes five quarts of oil under a continuously pumped flow to keep the crankshaft from overheating its' bearings; unlubed ball bearings in the water pump shaft aren't going to last very long under those conditions.  Changing a water pump on a front-wheel drive car can sometimes be a daunting task, but it can be done by the amateur.