I have posted questions on waterpumps before and have found that it appears that the majority(if not all pump failures have been on pre-99 cars(mileage may be a factor).
Did extensive research and found that plastic is the only material that could be molded to produce an efficient design for water flow. The metal impellar is a lot more shallow than the plastic, and some resources have stated that correct flow in the head is not achieved(prone to hot spots).
Many manufacturers have been making plastic impellars in their effort to make things smaller and more efficient.
This may be a case of the wrong type of plastic being used in the early years.
I am going down the path of figuring out the resistance curve of the temp gauge so a warning buzzer is triggered when greater than normal temperture is seen..
