Quote:
Originally Posted by Yellowb1rd
replace them both at the same time. The waterpump is driven by the timing belt, is it not? It's a prudent decision, because this is an interference design, and if the waterpump fails/seizes and the timing belt snaps, you're starting all over again, except with damage to the head to address on top of it. You replace them both at the same time, and it takes the ??? out of the equation.
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Are you suggesting that if the waterpump seizes first, then the static waterpump pulley could cause the timing belt to break? I imagine in such a scenario one would see the coolant temp skyrocket and could pull over before the belt breaks. The pulley is not a sprocket design. If it was, then I would easily understand how a seized pulley would cause the timing belt to immediately break, but it's not. Also, the waterpump pulley is not on the driven side of the belt but on the return side so it should have a little extra slack.
I feel that if you properly tension the new timing belt on the low side of factory range, then the load on the waterpump pulley shaft isn't enough to cause any likely problems.
However, if I found myself in a scenario where the coolant suddenly skyrocketed, I would pull over but I would NOT wait for the car to cool and attempt a restart. A seized pulley could cause the timing belt to loosen the belt tension and cause the belt to jump teeth upon restart with the starter motor.
I think that a waterpump is a lot more likely to fail than seize and the only way a waterpump could break our timing belt is if coolant were to leak onto the belt for a period of time. I say check for coolant leaks at the 3000 mile belt retension to put your mind at ease.