[irox]

Hi Noriyasu,

I have repaired a Subaru (1990 Legacy with the 2.2L engine) that has a seized water pump. From what I can tell, once the pump stops turning (or stiffens up and becomes hard to turn), the time belt will continue to rub over the WP pulley, this puts tension in part of the belt (as the seized pulley now pulls on the belt) putting extra stress on the idler pulleys. Eventually the idler pulley bearing will fail, shooting ball bearing every where and causing the timing belt to come off.

Fortunately the 3.3 and 2.2 engines are non-interference engines and the vehicle could be repaired. Although I think the incident would shorten the life expectancy of the engine.

Even if your water pump doesn't seize completely, as it degrades it will get stiffer to turn, the this put stress on other components driven by the timing belt.

I do agree that it is also easier to change the PW when you do the timing belt, but there are good reasons to change it before it fails.