All the foam from the original core must be carefully removed, cleaned, & transferred to the new core before installation.
Note that, everywhere this TSB mentions "electrolysis", the correct term is "galvanic action". Electrolysis is the breakdown of the molecules in an electrolytic solution into their component chemicals due to an electrical charge being applied to the solution. (Hydrogen being emitted from a battery under a hard charge is an example of electrolysis since the water is breaking down into Hydrogen & Oxygen.) Luigi Galvani studied the interaction of electricity & metals exposed to an electrolytic solution. Since the phenomenon described in the TSB deals with the metal of the heater core & not the chemistry of the coolant, it's a galvanic process.
TSB 06-21-19 Heater Core Leakage and Electrolysis
Publication Date: 10/30/06
FORD: 1997-2002 Contour
1997 -2007 Crown Victoria, Mustang, Taurus
2005-2007 Five Hundred, Freestyle
1997-1999 F-2S0 Light Duty
1997 -2003 Windstar
1997-2007 E-Series, Expedition, Explorer, F-150, F-53 Motorhome Chassis, F-Super Duty, Ranger
2001-2003 Explorer Sport
2001-2007 Escape, Explorer Sport Trac
2004 F-15O Heritage
2005-2007 Escape Hybrid
1999-2007 F-650, F-750
LINCOLN: 1997-2002 Continental
1997-2007 Town Car
2000-2006 Lincoln LS
2006-2007 Mark LT
MERCURY: 1997 -2002 Cougar, Mystique
1997-2007 Grand Marquis
2006-2007 Mariner Hybrid
This article supersedes TSB 01-15-06 to update the vehicle model years and Service Procedure.
ISSUE: The majority of repeat heater core leaks are due to high flow rate or use of poor quality coolant. However, electrolysis should also be checked, especially when repeat repairs have occurred.
ACTION: If the heater core is leaking, review the location of the leakage and check the condition of the coolant.
1. If leaks are found on the inlet (or outlet) tubes entering / exiting the heater core, it is most likely due to due to high flow rate. Replace the heater core and install a restrictor in the heater hose closest to the engine block, reference Workshop Manual, Section 412.
2. lf leaks are found in the body of the heater core itself, and they do not appear to be the result of physical damage like contact or puncture, check the coolant for possible electrolysis.
Testing For Electrolysis
Check for voltage in the cooling system by touching the negative contact of a voltmeter to the battery ground or a known good ground and suspend the positive lead in the coolant, making sure it is in contact with the coolant, but not touching any metal part of the radiator or cooling system. Both AC and DC voltages must be checked. Vehicles normally have DC voltages; however, a faulty engine block heater or faulty diode in the alternator can produce AC voltages. It is understood that coolant is lost due to heater core failure but try to obtain a voltage reading on the old coolant in the engine block before addition or replacement. To keep more coolant from exiting the heater core, clamp off heater core lines and measure coolant in the engine block. Try not to dilute the original coolant with new coolant during testing if possible.
1. Determine whether coolant condition is acceptable.
a. Remove both cables from the battery and ensure they do not contact each other or the vehicle.
b. Touch negative lead of DC voltmeter to engine ground and positive lead in the coolant.
NOTE POSITIVE TEST PROBE IS IN THE COOLANT FOR TESTING.
c. Check the voltage in the cooling system. If less than or equal to 0.4 volts (VDC) OK, reconnect battery cables and proceed to Step 2.
d. lf greater than 0.4 V, flush cooling system thoroughly.
e. Recheck voltage less than or equal to 0.4 V.
f. Reconnect battery cables.
g. Refill the system with appropriate Motorcraft® engine coolant.
2. Check for loose or missing grounds at static conditions.
a. Turn off all accessories. Turn ignition on but do not start engine.
b. Test with ground probe to battery ground, engine ground, and vehicle ground sequentially.
c. Voltage less than or equal to 0.4 V on all grounds OK.
d. Any one greater than 0.4 V, check and clean ground cable connections.
e. Check accessories without using the on/off switch on the vehicle instrument panel; use a jumper wire to ground.
f. Plug in engine block heater, if equipped, and test.
g. Recheck voltage less than or equal to 0.4 V.
h. Unplug engine block heater, if equipped.
3. Check for loose, missing, or inadequate grounds.
a. Test with ground probe to battery ground, engine ground, and vehicle ground sequentially.
b. Crank engine but do not start.
c. Monitor voltage while cranking. Less than or equal to 0.4V OK
d. If greater than 0.4 V, ground or repair starter.
e. Start engine and run at about 2000 rpm.
f. Turn on all accessories including those customer only uses occasionally such as CB radio, cell phone, etc.
g. Test with ground probe to battery ground, engine ground, and vehicle ground sequentially.
h. Voltage less than or equal to 0.4 V OK
i. If greater than 0.4 V, turn off one item at a time until voltage drops to less than or equal to 0.4 V. Repair ground to the accessory just identified.
j. Recheck voltage less than or equal to 0.4 VDC
k. Turn the DVOM to AC volts.
l. Check for ANY AC voltage greater than 0.4.
m. If any AC voltage is present, try turning off each accessory one at a time including blower motor and any fan motors.
n. If AC voltage is still present, shut engine off and remove B from the alternator and tape it up, then retest.
o. If voltage drops gradually to less than or equal to 0.4 VAC, the ground straps may simply be overloaded by added accessories. Test by using a heavy gauge jumper to ground. If indicated, install heavier gauge ground strap(s) and recheck.
NOTE If vehicle is equipped with electric cooling fans, be sure they cycle during this testing and monitor voltage when they are on, and off.
CAUTION: DO NOT GROUND HEATER CORE. IF THE HEATER CORE IS GROUNDED, YOU HAVE PROVIDED THE ELECTROLYSIS A PATH THROUGH THE HEATER CORE. THIS WOULD CAUSE THE HEATER CORE TO BECOME AN ANODE OR RECEIVER AND IT WOULD PROMOTE THE ELECTROLYSIS, OR ANY STRAY VOLTAGE TO USE THE COOLANT AS THE GROUND PATH.
4. Refill the engine cooling system, reference Workshop Manual, Section 303-03.
NOTE IF THE HEAT OUTPUT IS INSUFFICIENT, OR IF THE ENGINE DOES NOT REACH NORMAL OPERATING TEMPERATURES, VERIFY PROPER THERMOSTAT OPERATION AND REPEAT PROCEDURE IF REQUIRED.
WARRANTY STATUS: Eligible Under Provisions Of New Vehicle Limited Warranty Coverage
Note that, everywhere this TSB says "electrolysis", the correct term is "Galvanic action".
TSB 01-15-06 Repeat Heater Core Failure
Publication Date: JULY 26, 2001
FORD: 1985-94 TEMPO
1985-2002 CROWN VICTORIA, ESCORT, MUSTANG
2000-2002 ESCORT ZX2, FOCUS
1985-90 BRONCO II
1985-97 F-250 HD, F-350
1985-2002 ECONOLINE, F-150, RANGER
1988-97 F SUPER DUTY
1999-2002 SUPER DUTY F SERIES
2001-2002 ESCAPE, EXPLORER SPORT TRAC, EXPLORER SPORT
LINCOLN 1985-92 MARK VII
1985-2002 CONTINENTAL, TOWN CAR
1993-98 MARK VIII
MERCURY: 1985-94 TOPAZ
1985-2002 GRAND MARQUIS
ISSUE: Some vehicles may exhibit (repeat) heater core leaks. This may be caused by a chemical reaction called electrolysis. Electrolysis involves an ion exchange between the heater core and engine coolant which can result in a breakdown of the heater core material. This is similar to the operation of a battery.
ACTION: Check for electrolysis on any vehicle with a heater core failure. If electrolysis is verified, flush the coolant and follow additional steps as required. Refer to the following Service Procedure for details.
SERVICE PROCEDURE - Electrolysis Inspection:
If there is a condition of a heater core leaking or repeat heater core leak, check for electrolysis using the following procedure:
1. To check for electrolysis use a DVOM set on DC volts. Place the positive probe of the meter in the engine coolant and the negative probe on the negative battery post.
2. Adjust engine throttle to 2000 RPM to properly get coolant flow and true electrolysis voltages.
3. If more than .4V is recorded, flush the coolant and recheck (follow guidelines in TSB 98-23-16 for Cougar). See Coolant Fill Procedure below to remove trapped air on 4.6/5.4/6.8L modular engines.
NOTE: EXPORT MARKETS, BE SURE THE WATER IS DESALINATED.
4. If there is still excessive voltage present in the coolant, check the engine to body/battery grounds. Also, verify proper grounding of any aftermarket electrical/electronic equipment which has been installed into the vehicle. Improperly grounded electrical devices can cause electrolysis to occur.
5. If the condition is still present after the grounds have been checked, it may be necessary to add extra grounds to the heater core and engine. A hose clamp can be used to secure a 16 AWG stranded copper wire to the heater core inlet tube. The other end should be secured to an EXISTING FASTENER on the body sheet metal. Extra grounds to the engine should be attached between EXISTING FASTENERS on the engine and body sheet metal. Verify continuity of any added grounds to the negative battery terminal.
6. If the condition is still present, add a restrictor (part F1UZ-18D406-A) on the inlet hose with the arrow facing the direction of coolant flow (toward heater core). Cut the line and install with 2 hose clamps. It is important that the restrictor be installed in the right direction of flow and as close to the engine block as possible (not near the heater core itself).
Coolant Fill Procedure
At times, in order to completely remove any trapped air in the cooling system of vehicles equipped with 4.6/5.4/6.8L modular engines, it may be necessary to use the following procedure:
1. Disconnect the heater hose at the right front or rear of the engine.
2. Remove the thermostat and housing.
3. Using the thermostat opening, carefully fill the engine with the proper clean coolant mixture until observed at the engine side heater hose connection.
4. Reconnect the heater hose and reinstall the thermostat and housing.
5. Fill the degas bottle to the coolant fill level mark.
6. Run the engine until it reaches normal operating temperatures.
7. Select max heat and max blower speed on the climate system.
NOTE: IF THE HEAT OUTPUT IS INSUFFICIENT, OR THE ENGINE DOES NOT REACH NORMAL OPERATING TEMPERATURES, VERIFY PROPER THERMOSTAT OPERATION AND REPEAT PROCEDURE IF REQUIRED.
PART NUMBER PART NAME
OTHER APPLICABLE ARTICLES: 98-23-16
WARRANTY STATUS: INFORMATION ONLY