I NEED SOME OPINIONS IF I CAN GET SOME HELP PLEASE, I HAVE A 99 CHEVY SILVERADO WITH ABOUT 126,000 MILES, JUST RECENTLY MY WATER PUMP STARTED TO LEAK SO I REPLACED IT WITH A NEW ONE AND A NEW THERMOSTAT. SO I INSTALLED THE WATER PUMP AND THERMOSTAT AND AFTER I DID THAT AND PUT ANTIFREEZE IN IT THE TRUCK STARTED TO OVER HEAT, SO I THOUGHT IT MIGHT BE THE THERMOSTAT, SO I REMOVED IT AND CHECKED IT AND WHEN I DID THAT I SEEN A LOT OF SLUDGE THAT CAME OUT THE NEW WATER PUMP I GUESS DUE TO THE RADIATOR AND HEATER CORE, SO I FLUSHED THE SYSTEM OUT GOOD, THEN I PUT MORE ANTIFREEZE AND THE TRUCK STILL SEEMS TO BE OVERHEATING, THE TEMP GUAGE STAYS AT 210 DEGREES AND MOVES BACK AND FORTH, IS THIS NORMAL, LET ME KNOW WHAT YA COME UP WITH, ALSO EVERYTHING ELSE IS ORIGINAL NOT REPLACED.

 

There might be a air pocket in the cooling system.

Was it overheating before your replaced the waterpump?

 

It is the Dex-Cool Red Anti Freeze - See my post on it on first page. You may even have a head gasket startingto go. I provided many links that will **** you off. Sorry to hear it hit you.
GL
Greek