There's some confusion. If you had the cooling system tested it should be leaking coolant, not water, unless you only have water in the cooling system. If that's the case, water doesn't have the same seal conditioners and water pump lubricant that is in antifreeze. That alone could lead to a leak. If it is indeed the cooling system that's leaking and it's near the front of the engine, the water pump is the most likely suspect, especially given that it leaks when it cools down. The lip seal around the shaft will balloon up and seal better when pressure builds up in the system. It will relax and open up and leak when there's no pressure.
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Wednesday, April 6th, 2011 AT 3:45 PM