Read this before you replace the heater core.
Hello to all:
Like so many others, my '97 F-150 has begun to intermittently generate an antifreeze smell/mist/fog into the truck.
During my research of the problem I discovered that the Ford CD manual suggests that sometimes the problem is not with the heater core, but rather with the coolant lines connecting the heater core to the engine.
I have copied that information from the manual and will post it here for future reference for all F-150online members.
From the Ford Manual on CD:
WARNING: CARBON MONOXIDE IS COLORLESS, ODORLESS AND DANGEROUS. IF IT IS NECESSARY TO OPERATE THE ENGINE WITH THE VEHICLE IN A CLOSED AREA SUCH AS A GARAGE, ALWAYS USE AN EXHAUST COLLECTOR TO VENT THE EXHAUST GASES OUTSIDE THE CLOSED AREA.
1. Note: Testing of returned heater cores reveals that a large percentage of heater cores are good and should not have been replaced. If a heater core leak is suspected, the heater core should be tested as outlined in the Plugged Heater Core procedures before pressure testing the heater core. Perform a system inspection by checking the heater system thoroughly as follows:
Inspect for evidence of coolant leakage at the heater water hose to heater core attachments. A coolant leak in the heater water hose could follow the heater core tube to the heater core and appear as a leak in the heater core.
2. Check the integrity of the heater water hose clamps.
3. Spring-type clamps are installed as original equipment. Use of non-specification clamps can cause leakage at the heater water hose connection and damage the heater core.
Plugged Heater Core
WARNING: THE HEATER CORE INLET HOSE WILL BECOME TOO HOT TO HANDLE IF THE SYSTEM IS WORKING CORRECTLY.
Check to see that the engine coolant is at the proper level. Start the engine and turn on the heater. When the engine coolant reaches operating temperature, feel the heater core outlet hose to see if it is hot. If it is not hot, the heater core may have an air pocket or may be plugged, or the thermostat is not working properly.
Use Radiator/Heater Core Pressure Tester to perform the pressure test. Note: Due to space limitations, a bench test may be necessary for pressure testing.
1. Drain the coolant from the cooling system.
2. Disconnect the heater water hoses from the heater core.
3. Install a short piece of heater water hose, approximately 101mm (4 inches) long on each heater core tube.
4. Fill the heater core and heater water hoses with water and install plug and adapter from Radiator/Heater Core Pressure Tester in the heater water hose ends. Secure the heater water hoses, plug and adapter with hose clamps tightened to specifications.
5. Attach the pump and gauge assembly from Radiator/Heater Core Pressure Tester to the adapter.
6. Close the bleed valve at the base of the gauge and pump 241 kPa (35 psi) of air pressure into the heater core.
7. Observe the pressure gauge for a minimum of three minutes.
8. If the pressure drops, check the heater water hose connections to the core tubes for leaks. If the heater water hoses do not leak, test the heater core as follows:
a. Drain all coolant from the heater core.
b. Remove heater core from the A/C evaporator housing.
c. Connect the 101mm (4 in) test heater water hoses with plug and adapter to the core tubes. Then connect the Radiator/Heater Core Pressure Tester to the adapter.
d. Apply 241 kPa (35 psi) of air pressure to the heater core. Submerge the heater core in water.
e. If a leak is observed, service or replace the heater core (as necessary).
This thread is a revision of a thread I had previously posted under a different title. There was a typo in the title, and was therefore somewhat misleading. I tried, but was unable, to delete the previous thread. Paul Wilkinson