Obstructed Coolant Flow

Possible locations or causes of obstructed coolant flow are as follows:

• Low coolant level.
• Inoperative water pump.
• Inoperative thermostat.
• Pinched or kinked heater hoses.
• Improper heater hose routing.
• Plugged heater hoses or supply and return ports at the cooling system connections.
• Plugged heater core.

If proper coolant flow through the cooling system is verified, and heater outlet air temperature is low, a mechanical problem may exist.