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Replacing a heater core in a 1989 Ford Bronco (fourth generation 1986 to 1991)

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The Ford Bronco was one of the first sport-utility vehicles: rough and versatile it was used for everything from pulling a trailer, to plowing snow, to off-road fun, etc. Many fourth generation – 1986 to 1991 – Broncos are still on the road today and a favorite of truck enthusiasts. Replacing the heater core in your Ford Bronco may look daunting, but it’s actually not too hard.

Remove heater hoses
Remove heater hoses Art Heberger

Remove heater hoses

  • Drain about a quart of coolant from the radiator, so it won't leak all over your engine compartment and the ground.
  • Loosen the two clamps, and remove the heater hoses attached to the core. If they're hard to get off, twist them with pliers -- or hose pliers if you have them.
Remove the glove compartment
Remove the glove compartment Art Heberger

Remove the glove compartment

  • Remove all the gloves from your glove compartment -- or anything else that may be lurking in there.
  • Hold the glove compartment and pull the pin out of the stop strap.
  • Lower the glove box until you can slide it off the hinges.
  • Remove the glove compartment and set it aside.
Remove the heater core cover
Remove the heater core cover Art Heberger

Remove the heater core cover

  • Remove the clips holding the heater door cable and any wires that are attached to the cover.
  • Remove the eight bolts securing the heater core cover to the heater box.
  • Guide the cover over the core and remove it.
  • Wipe any dirt, debris or coolant from the inside of the cover.
Remove the core
Remove the core Art Heberger

Remove the core

  • Pull the heater core straight out of the heater box until the inlet and outlet tubes are clear of the holes in the firewall.
  • Guide the heater core down until it is clear of the dashboard and heater box.
  • Clean any dirt, debris and coolant from the inside of the heater box with a rag.
Install the replacement heater core
Install the replacement heater core Art Heberger

Install the replacement heater core

  • Install the replacement heater core, guiding the inlet and outlet tubes carefully through the firewall. If possible have someone help you from the engine compartment side.
  • Check the seal around the heater box to make sure it is properly in place.

Do not force the core if it gets stuck, you could end up cracking a solder joint and causing a leak.

Fill the cooling system
Fill the cooling system Art Heberger

Fill the cooling system

  • Install one of the heater hoses and tighten the clamp.
  • Place the other hose in a clean container.
  • Slowly fill the radiator until coolant starts to come out of the hose.
  • Install the hose and tighten the clamp.
  • Start the engine with the radiator cap off and run it until it gets to operating temperature -- when you see the coolant circulating in the radiator.
  • Install the radiator cap and let the engine run for about five minutes.
  • Check for leaks.
  • Install the heater core cover.
  • Install the glove compartment.