Is it necessary to change the water pump when changing the timing belt?
If the water pump is driven by the timing belt it’s a VERY GOOD IDEA to replace them both at the same time.
Necessary, no. Smart, yes.
If you don’t replace the water pump now, and it goes bad in six months, you will pay the same labor charges to replace the pump that you are about to pay to replace the timing belt, since the effort involved to replace either one is the same. Paying twice is not a good idea.
Pay once. Have a new water pump installed along with the timing belt. It’s the smart thing to do.
I’ve changed the timing belt on a 1992 300ZX and although the water pump is NOT driven by the timing belt it still is a good idea to change the water pump at the same time because of the labor involved.
And any belt tensioners and idlers should also be replaced. I think this is an interference engine and if a worn idler or tensioner was to seize up or come apart this will snap the new belt and you are going to suffer some engine damage.