A coolant leak may develop from the water pump. This can result in an engine overheating condition. A leaking water pump will require replacement.Google+
Car Problem Reports
Chevrolet Blazer Leaking Water Pump May Cause Coolant Loss and Overheating
Chevrolet Blazer Problem
Visitor, 1998 Chevrolet Blazer, 60,000 mi
heat only at higher rpm, gurgling sound in heater core. loss of coolant allows heater core to air lock (its higher than the radiator). stains on bottom of pump by bearing "weep" hole show pump slings out coolant while running. replaced pump and parked facing uphill to to top off radiator.