Cooling Problem Solvers Problem Cause Cure Overcooling 1. Inoperative thermostat 2. Inaccurate temperature gauge 1. Replace thermostat. 2. Replace temperature (gauge, cylinder). Poor circulation 1. Restriction in system 2. Insufficient coolant 3. Inoperative water pump 4. Loose fan belt 5. Inoperative thermostat 1. Check hoses for crimping. 2. Clear the system of rust and sludge. 3. Replenish. Replace (dirty water, water pump). 4. Adjust fan belt. 5. Replace (thermostat, gauge). Corrosion 1. Excessive impurity in water 2. Infrequent flushing and draining of system 1. Use soft, clean water. 2. Flush thoroughly at least (once, twice) a year.