Yesterday morning I started my car up to warm it up, The car began to overheat. The temp shot up almost to the red mark past the halfway point. The water coolant resevoir was boiling to the point that it shot the cap off. So I turned the car off and waited a few minutes. Turned it back on and everything was fine. Fans kicked in normally and everything was good. This morning, more of the same. Not to the point of the resevoir boiling though. I turned the car on and instead of the normal 10 minutes that it takes to warm, the temp started rising almost instantly. Once I began driving everything seemed fine until I got about 3 miles down the road where the temp began to rise again. It kept rising rapidly and then shooting back down even faster it seemed. Until it got to the point where it began to get real close to the red mark again. I pulled over on the highway and instantly it went back down. For the rest of my ride she seemed fine. Temp seemed a little jittery at times in the begining once I got back on the highway after pulling over but she smootyed out and stayed cool. I guess the fans kicked in and did there job. For the most part the rest of my trip to work the temp seemed normal. Never rose past a 1/4 of the way. This past week the belt or what I think is the belt started squeeling. Only does it when I first turn the car on and shes cold. Stops once the cars is warm or if it has already been driven it wont do it at all. I changed the oil last week. I replaced the thermostat in the summer, so I dont think its that. Waterpump was replaced about a year ago. Radiator replaced about 2-3 years ago. Any ideas on what Im looking at here? I changed the belt about 2 years ago as well. Would a bad belt do this or is the squeeling coincidental and Im looking at something completely unrelated?

 

I know you said you replaced the pump, but run the car with the radiator cap off and make sure coolant is actually flowing, could be a junk water pump. Could be an air pocket as well.... Running the car with the cap off may take care of that. Are you getting heat in the cabin?

 

A squealing belt usually means a loose belt but it could also be the pump binding at least some of the time. ??? Also, just because you replaced something doesn't mean it's not the problem. Follow the diagnostics.