The heater core in my 93 is leaking and I have to replace it. Its been a few years since I replaced one in a Mark VIII. I know that you have to drop the steering column and pull the dash(uuuggghhhh...), but does anyone have any tips to make the job quicker? I really want to drive the car, but its damn cold over here. And, its hard to set aside time to work on my own stuff since I have a lot of side work that I need to finish too.

Dave
MM1(SW)-N NSSA NRFK FMB
94 Mk8 Mark VIII Under Construction
90 Cougar XR7 Showing signs of life...
81 Rabbit 1.6D 50-60mpg

The hard part is dealing with the hoses.

Buy new heater hoses before you do the following.

I suggest you grab a long flat-head screwdriver, and use it to stab, scrape and pry at the old hoses under the hood at the firewall till they break free from the heater core pipes. It'll be easier to pull the old core out that way.

Once you've bolted the new core in, be sure to electrically ground it, so it won't corrode like your last one.

Dielectric grease smeared on the hose fittings will help you slide the new hoses on easier.

Good idea, I would never have thought of that! Grounding the heater core. Makes sense, since the cooling system does develope a voltage potential as the coolent ages, or things go wrong.

Dave
MM1(SW)-N NSSA NRFK FMB
94 Mk8 Mark VIII Under Construction
90 Cougar XR7 Showing signs of life...
81 Rabbit 1.6D 50-60mpg

yes the grounding of the heater cores is the #1 reason they fail on Fords. When coolant is neglected you get this potentail effect even more. We would see this in the shop frequently.

formerly ASE certified, still skin my knuckles
98 Mark VIII Silver

Maybe you know, and maybe you don't, but you need to remove the wiper cowling for access to the hoses at the firewall.

And you won't like this one and I offer it only as a last ditch effort, but if you can't in anyway get to those hidden hoses, if you remove your intake manifold, you will get a lot more access.

MOD aka "another Craig"
Mark of Distinction
1993 Light Mocha

here are the details of the Ford TSB:

Article No.: 01-15-6
Date: 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:
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.
Adjust engine throttle to 2000 RPM to properly get coolant flow and true electrolysis voltages.
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.
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.
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.
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).

formerly ASE certified, still skin my knuckles
98 Mark VIII Silver

Thanks for the additional info. I have definetly seen vehicles come in with >.3V(our cut off voltage), which we would then flush and not be able to get less than .2V.

Dave
MM1(SW)-N NSSA NRFK FMB
94 Mk8 Mark VIII Under Construction
90 Cougar XR7 Showing signs of life...
81 Rabbit 1.6D 50-60mpg

I've gotten my heater hoses off without removing the wiper cowl. The only difficulty was that these were the hoses that were installed on the car in '93, and they were not about to let go without a fight.

I had to destroy the old hoses by stabbing multiple holes in them in succession till the hoses were practically holding together by a thread. When I thought I had done enough damage, I tugged on the hoses and tore them free. I reached the hoses through the area where the transmission dipstick is located.

The factory clamps can be pried-off using the screwdriver once the hoses are cut off.

I replaced those clamps with the screw-type hose clamps.

Yeah, those are called spring-clamps, and the manufacturers love using them because they are cheap. I have a spring-clamp remover($100, but worth it) that makes taking those off easy in just about any position.

Dave
MM1(SW)-N NSSA NRFK FMB
94 Mk8 Mark VIII Under Construction
90 Cougar XR7 Showing signs of life...
81 Rabbit 1.6D 50-60mpg

The hard part is getting the new heater hoses installed behind the engine with only 3" of clearance to get your hand in there. Any tips on performing this difficult task?

mark

Break it Good, then Fix it Right.

Yeah! Sure do. Move stuff out of the way so that you have more room. If you have a 93-96, remove the fuel lines at the quick disconnects and push them as far as you can over to the passenger side. Use a bungie cord to hold them in place if you have to. Also, if you are having a hard time, remove the plastic 90 degree piece that guides the fuel lines. Then, remove the transmission dip-stick. Also, if you had some bone head put hose clamps on it already with the fasteners facing down, remove the IAC. You will need to use two swivels on the bolt on closer to the intake. Its tough any way you look at it.

Dave
MM1(SW)-N NSSA NRFK FMB
94 Mk8 Mark VIII Under Construction
90 Cougar XR7 Showing signs of life...
81 Rabbit 1.6D 50-60mpg