I used to own a 88 mustang convertible when I was 16 and I had the unfortunate task of having to replace the heater core. I completed the job in about 2 days with multiple screws left over. I didn't care though, I had heat and it was all good.

Fast Forward 9 years. I am now 25 and own a 91 SSP as a toy and when I rebuilt the engine as I was setting it in, the valve cover caught the heater core pipe at the firewall and it bent downward. I hoped and prayed nothing happend to the core but once I got everything connected and fired the engine up, there was a constant stream of antifreeze landing on the headers from the Firewall drain. I bypassed it and thought, its just a toy, I wont worry about heat. I got a little more indepth with the car than I ever thought I would and have now almost completed a full restoration on it. So I began to realize that I would soon have to replace the heatercore like it or not.

That time came last week. I was in the shop and I had a slight leak from the water pump because during the HCI install I damaged the gasket that goes between the water pump and the backing plate. So I decided to try to silicone it back on and see if that would hold, It didn't. So I ordered a new water pump, and figured, well I am this far, I might as well get it all done at the same time so I can start driving this thing once in a while. I ordered the heater hoses, the water pump, and the core and 2 gallons of antifreeze. Total cost was $64.

I remembered something about electrolysis being mentioned as part of heater core failure so I did some digging and found this TSB from Ford:

Article No.
01-15-6

08/06/01

^ CLIMATE CONTROL - REPEAT HEATER CORE FAILURE

^ COOLING SYSTEM - REPEAT HEATER CORE FAILURE

FORD:
1985-1994 TEMPO
1985-1997 THUNDERBIRD
1985-2002 CROWN VICTORIA, ESCORT, MUSTANG
1986-2002 TAURUS
1988-1993 FESTIVA
1993-1997 PROBE
1994-1997 ASPIRE
1995-2000 CONTOUR
2000-2002 ESCORT ZX2, FOCUS
2002 THUNDERBIRD
1985-1990 BRONCO II
1985-1996 BRONCO
1985-1997 F-250 HD, F-350
1985-2002 ECONOLINE, F-150, RANGER
1986-1997 AEROSTAR
1988-1997 F SUPER DUTY
1991-2002 EXPLORER
1995-2002 WINDSTAR
1997-2002 EXPEDITION
1999-2002 SUPER DUTY F SERIES
2000-2002 EXCURSION
2001-2002 ESCAPE, EXPLORER SPORT TRAC, EXPLORER SPORT

LINCOLN:
1985-1992 MARK VII
1985-2002 CONTINENTAL, TOWN CAR
1993-1998 MARK VIII
2000-2002 GLS
1998-2002 NAVIGATOR

MERCURY:
1985-1994 TOPAZ
1985-1997 COUGAR
1985-2002 GRAND MARQUIS
1986-2002 SABLE
1991-1999 TRACER
1995-2000 MYSTIQUE
1999-2002 COUGAR
1993-2002 VILLAGER
1997-2001 MOUNTAINEER

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 repeal 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).


I Completely disassembled the dash, with much more care this time than in previous times, and had the bad heater core in my hands in less than 2 hrs. Now, granted I know why this one failed, like I said, I bent the tubing and it broke. I will post pics of the failed core up later. I remember the headache that I went through the first time on my 88 and I knew this job was not easy nor fun, however this time it went much smoother as with age you get more patience, and you gain a better understanding, not to mention I have worked as a stereo installer for 7 years now at best buy and have plenty of experience with taking dashes apart, plus an excellent mechanical background. But I wanted to prevent any issues from the electrolysis TSB from having me go back into this dash any time within the near future. So what I did was solder a wire to the back tank of the heater core and ran it out of the heater box. I then put a ring terminal on the wire and grounded the wire to the body of the vehicle that way it will not arc or build up a static charge, instead it will just pass the current through the wire and return it to the ground path of the vehicle. This is a little extra step that shouldnt take more than 10 mins and prevent one heck of a headache down the road, not to mention it looks better than the hose clamp and wire idea as suggested in the TSB because it is on the backside of the firewall behind the dash so it will not be seen. I have a few pictures to give you all a better idea of what I am talking about, for those of you who haven't tackled this job yet. Oh and as far as soldering the wire goes, just dont apply too much heat to the heater core and you wont to any damage to it, and in the end check the resistance across the heater core using a DMM put one lead on the inlet or outlet pipe and the other on the end of the wire you soldered on, your resistance should be around .5 ohms.

 

olllldddd newsss

i have one on mine

 

Sorry if its a repost, I was just trying to help out the people who didnt know.

 

i know, i put a smilely face. i think aode posted this once before. but its very very good info for those who dont know yet. honestly i think it should be stickied in the tech section.

 

been there done that one

 

....me too...too many times

 

That is something I did not know, along with about everything else I read on these posts... lol!!! When I get around to not being lazy I will definitely do that (even though mine doesnt fall in those year ranges) just so I got that little insurance and I dont have to do it over. Thanks for the info.