Heater Core Failure Due to Electrolysis
One of the major causes of heater core failure is electrolysis. Electrolysis is caused by elevated stray voltage in the coolant that flows through the cooling system. These stray voltages result from improper system grounding, and result in electrochemical reactions that etch away the surface of metals that come in contact with the coolant throughout the cooling system.
While most of the metal throughout the cooling system is very thick (e.g., engine blocks and heads) and is not generally damaged by the electrolysis, the thin aluminum coolant tubes in the heater core and the main radiator are continuously being eroded away. Because these tubes are very thin to facilitate heat dissipation, they eventually pit or rupture and begin to leak the hot pressurized coolant into the passenger compartment.
TIP: The only correct way to fix a leaking heater core is to replace it. While there are cooling system 'stop leak' products on the market that may slow or even stop small leaks for a period of time, these are only temporary band-aids and may even cause additional damage to your cooling system or other vehicle systems. Use of these products is not recommended.
The cooling system electrolysis problem has been found to be very widespread and to exist in many models. Some manufacturers have recognized the problem and have issued Technical Service Bulletins to address the issue. For example, in 2001 Ford Motor Company issued TSB 01-15-6 that discussed (repeated) electrolysis-induced heater core failure in many Ford, Mercury and Lincoln models spanning model years 1985 through 2002.
In 2006, TSB 01-15-6 was superseded by TSB 06-21-19, which covers the electrolysis problem in over 200 additional models of Ford, Lincoln and Mercury vehicles spanning model years 1997 through 2007.
Strangely, there was no mention of model years 1985 through 1996 in the current TSB. We are not sure if this indicates that all the electrolysis issues have been resolved in those earlier models, or if they simply didn't list any vehicles over 10 years old. One also has to wonder what the electrolysis prognosis may be for vehicles newer than 2007. The jury is still out on these issues, but we will let you know as soon as we find answers.
We strongly recommend that you check these TSBs to see if your vehicle is included. If you own one of these vehicles, you should get a copy of these TSBs so you can better understand the problem and the measures you can take to help prevent repeated heater core failures in your own vehicles.
To download a complimentary copy of the current TSB, simply submit the form below and then click on the TSB Download icon beneath the form.
Models Covered by TSB 16-21-19:
FORD MERCURY LINCOLN
1997 Contour 1997-2002 Cougar 2003-2005 Aviator
1998 Contour 2004-2007 Freestar 2002-2003 Blackwood
1999 Contour 1997-2007 Grand Marquis 1997-2002 Continental
2000 Contour 2005-2007 Mariner 2000-2006 Lincoln LS
2001 Contour 2006-2007 Mariner Hybrid 2006-2007 Mark LT
2002 Contour 2006-2007 Milan 2007 MKZ
1997 Crown Victoria 2005-2007 Montego 1998-2007 Navigator
1998 Crown Victoria 1997-2007 Mountaineer 1997-2007 Town Car
1999 Crown Victoria 1997-2002 Mystique 2006 Zephyr
2000 Crown Victoria 1997-2005 Sable
2001 Crown Victoria 1997-2002 Villager
2002 Crown Victoria
2003 Crown Victoria
2004 Crown Victoria
2005 Crown Victoria
2006 Crown Victoria
2007 Crown Victoria
1997 E-Series
1998 E-Series
1999 E-Series
2000 E-Series
2001 E-Series
2002 E-Series
2003 E-Series
2004 E-Series
2005 E-Series
2006 E-Series
2007 E-Series
2001 Escape
2002 Escape
2003 Escape
2004 Escape
2005 Escape
2006 Escape
2007 Escape
2005 Escape Hybrid
2006 Escape Hybrid
2007 Escape Hybrid
2000 Excursion
2001 Excursion
2002 Excursion
2003 Excursion
2004 Excursion
2005 Excursion
1997 Expedition
1998 Expedition
1999 Expedition
2000 Expedition
2001 Expedition
2002 Expedition
2003 Expedition
2004 Expedition
2005 Expedition\
2006 Expedition
2007 Expedition
1997 Explorer
1998 Explorer
1999 Explorer
2000 Explorer
2001 Explorer
2002 Explorer
2003 Explorer
2004 Explorer
2005 Explorer
2006 Explorer
2007 Explorer
2001 Explorer Sport
2002 Explorer Sport
2003 Explorer Sport
2001 Explorer Sport Trac
2002 Explorer Sport Trac
2003 Explorer Sport Trac
2004 Explorer Sport Trac
2005 Explorer Sport Trac
2006 Explorer Sport Trac
2007 Explorer Sport Trac
2005 Five Hundred
2006 Five Hundred
2007 Five Hundred
2004 Freestar
2005 Freestar
2006 Freestar
2007 Freestar
1997 F-53 Motorhome Chassis
1998 F-53 Motorhome Chassis
1999 F-53 Motorhome Chassis
2000 F-53 Motorhome Chassis
2001 F-53 Motorhome Chassis
2002 F-53 Motorhome Chassis
2003 F-53 Motorhome Chassis
2004 F-53 Motorhome Chassis
2005 F-53 Motorhome Chassis
2006 F-53 Motorhome Chassis
2007 F-53 Motorhome Chassis
1997 F-150
1998 F-150
1999 F-150
2000 F-150
2001 F-150
2002 F-150
2003 F-150
2004 F-150
2005 F-150
2006 F-150
2007 F-150
2004 F-150 Heritage
1997 F-250 Light Duty
1998 F-250 Light Duty
1999 F-250 Light Duty
1999 F-650
2000 F-650
2001 F-650
2002 F-650
2003 F-650
2004 F-650
2005 F-650
2006 F-650
2007 F-650
1999 F-750
2000 F-750
2001 F-750
2002 F-750
2003 F-750
2004 F-750
2005 F-750
2006 F-750
2007 F-750
1997 F-Super Duty
1998 F-Super Duty
1999 F-Super Duty
2000 F-Super Duty
2001 F-Super Duty
2002 F-Super Duty
2003 F-Super Duty
2004 F-Super Duty
2005 F-Super Duty
2006 F-Super Duty
2007 F-Super Duty
2000 Focus
2001 Focus
2002 Focus
2003 Focus
2004 Focus
2005 Focus
2006 Focus
2007 Focus
2005 Freestyle
2006 Freestyle
2007 Freestyle
2006 Fusion
2007 Fusion
1997 Mustang
1998 Mustang
1999 Mustang
2000 Mustang
2001 Mustang
2002 Mustang
2003 Mustang
2004 Mustang
2005 Mustang
2006 Mustang
2007 Mustang
1997 Ranger
1998 Ranger
1999 Ranger
2000 Ranger
2001 Ranger
2002 Ranger
2003 Ranger
2004 Ranger
2005 Ranger
2006 Ranger
2007 Ranger
1997 Taurus
1998 Taurus
1999 Taurus
2000 Taurus
2001 Taurus
2002 Taurus
2003 Taurus
2004 Taurus
2005 Taurus
2006 Taurus
2007 Taurus
2002 Thunderbird
2003 Thunderbird
2004 Thunderbird
2005 Thunderbird
1997 Windstar
1998 Windstar
1999 Windstar
2000 Windstar
2001 Windstar
2002 Windstar
2003 Windstar
