Replace The Heater Core

I’ve been working on cars for twenty plus years and nothing, I mean nothing, was easier to install than the heater core on the 1993 Ford Explorer. I would say a child could install it!

I have heard that some vehicle models are difficult because a person can’t access the heater core very easily. I’ve also heard that you have to remove the dash. I have replaced the heater core on a 1 ton Chevy, a Mustang, a Pinto (yep, a Pinto!) and the Explorer and never have I had to remove a dashboard. The heater core on all four were straight forward and took less than an hour. The Mustang did require a couple of extra parts removed, compared to the Chevy, Pinto and Explorer, to access the heater core, but it was still child’s play. The Chevy was as easy as the explorer, but I didn’t take pictures of that installation, but I did of the Explorer installation!

Follow along with the directions and pictures and you’ll be roasting in no time.

The heater core is like a miniature radiator. The coolant from the engine flows through it as part of the cooling system.

First, the coolant in a warm engine flows through the engine, absorbing the heat.

Second, the hot coolant is diverted through the firewall into the heater core at the passenger area below the dashboard.

Third, when the heater is activated, a fan blows air across the heater core causing the warmth from the coolant, that is hot from the engine, to disperse into the cabin of the vehicle.

Last, the coolant flows out of the heater core, back through the firewall and to the radiator for additional cooling through the radiator and radiator fan.

When a vehicle is having an overheating issue it can sometimes help to turn the heater on high. With the heater on high it assists in cooling the coolant that the engine is having trouble cooling. It won’t fix an overheating issue but it may buy you some time to get to a service station or safe exit.

Is It The Heater Core?

Is the heater core the problem? Before purchasing, or removing parts, you’ll want to be sure that it is indeed the heater core that is the problem.

Fortunately, the heater core provides several indicators when it is going bad, or has gone bad. In order of what you may see first with a bad heater core:

  1. Does the windshield of the car have mist on the inside on occasion. This mist will get worse as the core goes bad. The mist will be noticeable near the dashboard at first where the heater vents for the defroster come out of the dashboard. It will slowly rise up the windshield as time passes.
  2. Depending on the contents of your radiator (some people insist on only putting water in their radiator to their digression). When the core starts to go bad you will notice an odor of radiator fluid, in the cabin of the vehicle. If water is in your radiator, you’ll notice an odor of boiling water.
  3. The floorboard of the vehicle, on the passenger side, will be wet.
  4. Lastly, the heater will turn on, but no heat will come out of the vents.

Sometimes, when a heater core goes bad, a quick fix some people choose instead of replacing the heater core, is to bypass it. To do that they remove the hoses, under the hood, and plug them into each other. This way the coolant bypasses the heater core (see photo). This was what was done on the Explorer. The person that bought it found out the hard way. When they were up in the snow and turned on the heater only cold air came out. When they popped the hood they saw the hoses were spliced together. That was a cold ride home!

Let’s Do This!

Only work on the cooling system when it is cool. If it’s warm, or hot, burns can occur from the coolant, besides the built up pressure that will burst out.

  1. Remove the two hoses under the hood, at the firewall, attached to the heater core pipes that are protruding through the firewall.
  2. Inside, on the passenger side, below the glove box, is a black, plastic cover with four screws in it, remove the four screws. ( There may be a decorative cover that would need to be removed first.)
  3. The plastic piece will drop down. Slide it outwards to allow the drain pipe, going through the firewall, to come through.
  4. You should be able to see the bottom of the heater core at this point. Pull it down while pushing towards the wall. The pipes can be pushed through the firewall, under the hood, by an assistant, if this helps.

And you’ve removed the heater core! Now let’s put it back in.

Install The New Heater Core

There may be insulation on the heater core you removed. If possible transfer it to the new core. If it can’t be removed pick some padding up at the hardware store and attach it as it is on the old one (this is not imperative, it’s just padding).

  1. Take the new heater core and slide it up where the old one was. Again, use an assistant to guide the pipes through the firewall if it will help. It can be difficult to line up the holes and push the pipes through at the same time.
  2. Once the pipes are through, attach the hoses, under the hood, to them. It helps to hold the heater core in place.
  3. Now put the plastic piece back on and screw in the four screws you took out earlier.
  4. If there was a decorative cover, replace that too.
  5. Open the radiator cap and top off the fluid that escaped when you took the hoses off.
  6. Start the engine and look for leaks at the firewall connection.

Job well done!!

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