Heater Core Diagnoses

the job of a heater core is to supply heat to your vehicle and provide cooling for the engine. the heater functions as a heat exchanger. cooling system maintenance is an important part of your vehicle maintenance. here is a case study:

1999
Mercury
Sable
190k

Complaints
lack of heat on high speed of the fan
heat would come out for 5 to 10 mins before it would go to cold


Problems found

verified the heater core wasnt leaking, verified the coolant was in good condition.
found the return hose for the heater core was warm not hot as the in let side.

Solution

Removed the heater core hoses located at the firewall.
used a garden hose to flush the heater core during this process i noticed rust and sludge coming from the outlet side of the heater core. flushed the heater core until clear water was coming out. repeated process for 30 mins flushing the heater core both in n out lets. reconnected the heater core. topped off the coolant. ran the vehicle at 2500 for 5 mins to warm the engine up. verified i had heat on high let the car idle for 30 mins still had heat.



some cases with the heat core being bad will have the following

1. smell of antifreeze when heater is in use
2. fog on the windshield plus the smell of antifreezr
3. passenger side floor will be wet
4. inlet hose will be hot but the outlet hose will be colder
5. vehicle runs slightly warmer then normal
6. lose of coolant over time
7. lack of heat


Proper flushing instructions

1. wait until vehicle has cooled down
2. remove the inlet and out let hose from the heater core at the firewall or engine compartment. making sure you have a drain pan to catch the antifreeze that will leak out.
3. using a garden house or small amount of air pressure from a blower will work also but both together will work the best.
4. being flushing the heater connect the house to one side at a time. repeat this for 30mins or longer depending on how bad your heater core is.
5. reconnect the hoses after you flushed the heater core
6. top off the coolant
7. run the engine until normal operation temperature verify you have heat
8. check for leaks