Well, when the bearings are jammed, there was quite a bit of torque from the timing belt doing it's damnedest to twist the water pump off the water pump cover (what you call the housing) -- that would seem to be the most likely cause. Cover may've been poor quality or heavily coroded -- hard to tell without looking at the piece.we replaced the water pump and timing belt 2 days back and it did not stop the leak. The water pump was bad as the bearing had all fallen off and the pump was jammed. So we replaced water pump and timing belt ..but that did not stop the leak and we found later that the water pump housing itself has a crack...what could have caused that ?
I found one which has all that ( item no W0133-1608494 ) on http://www.drivewire.com/products/toyota-camry/water-pump/7955/
Yes its a after market part. In fact its Bosch water pump..we assumed the water pump damage was the cause of leakage so we replaced it. But now the housing needs to be changed too. If I knew before I would have replaced the whole thing. But anyway I found the the Dorman water pump housing is compatible with 99 camry 4 cylWell, when the bearings are jammed, there was quite a bit of torque from the timing belt doing it's damnedest to twist the water pump off the water pump cover (what you call the housing) -- that would seem to be the most likely cause. Cover may've been poor quality or heavily coroded -- hard to tell without looking at the piece.
I assume this "pump" must have been aftermarket? Because when you buy a Toyota "water pump", you get the pump / gasket / and pump cover all in one unit -- that suggests to me the engineers designed it to be replaced as a unit, and it only comes in pieces for manufacturing reasons.