I myself have a 1990 s10 and I had a coolent leak comeing from my water pump gaskets so I figured why replace the gaskets and not the water pump since I was going to be down there anyways. So thats what I did it, made sense to me even though it wasnt over heating pryor, I also changed the thrmostat and when I started it up I had a excessive overheating problem for a few days I scambled to try and find the problem i.E. Rediator, temp sensor, cloged water ways ect. Becouse the water pump I bought was new not reconditioned. Well to make a long storie short I had to go back to square one it was the water pump it was bult wrong and pushing water in revirse and that was confirrmed by the parts house I bought it from when I took it back becouse they were curous also so they took it apart and found that was the reason for malfunctioning. I took the time to write this becouse I was doing research when I was going threw all of this and found this post so I thought I would share my experience and let you know that sometimes the culprit can be the new parts them selfs and please remember just becouse a part is new dose not mean its good, just some food for thought hope everything gose well and good luck!
P.S. I had my problem 2 days after your post so who knows maybe there is a bad batch of s10 water pumps going around its something to look into?
Friday, November 13th, 2009 AT 8:59 PM