There is some possibility that your water pump impeller may have started to deteriorate. In both my cars impeller failure was catastrophic and instantaneous, but I have read the posts of others where (when they were replacing as a pre-emptive measure) they found partially damaged impellers fins.
I think a replacement of wp might be the least risk place to start. If impeller damaged you've found problem, if not then new metal impeller will eliminate future potential problems.
p.s. What mileage is on car?
98 Mystique LS v6 atx 110,000km
97 Contour LX v6 atx 125,000km
stock CD on LS, cass on LX
spoiler, tinted windows on LS only
4 wheel discs on LX only
All other available options on both
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