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How to Replace Your Heater Core

About This How-to
Author: jakerooni
Added: 12.27.03
Updated: 02.28.04
Discuss (36)

This how-to shows you how to a broken heater core, which is a relatively common problem with the stock plastic units. It's not as hard as you think, and even first timers should be able to accomplish this in an hour or so.


  • New heater core (Get a metal one!)
  • Hose Clamps


  • 7/32" & 9/32" sockets
  • Pliers
  • Butter Knife (or other flat prying tool)

How To Do It

Step 1

Let's start by locating the Heater Core. Directly behind your center consol behing the Stereo you'll see a black casing underneath held up by a bunch of Different screws. This is the heater core caseing. You'll need to remove all these screws to get to the heater core. The actaual casing screws are 7/32" But you'll have a few 9/32" screw to contend with in getting to the casing.

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Step 2

Before you Can remove the Heater Core though you'll have to remove the 2 heater core lines connected to it from the engine side. Of course to do this your going to want your engine nice and cool your cooling system unpressurized. Also it's a good idea to get a bucket or something to collect the coolant that will spill all over the place. Pending on which way you decide to tackle this you can get to the lines either from the top of the engine (for smaller arms only) or jack up your car and get to the hoses from the bottom. I have included pics of either way.

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Step 3

When you take out all the screws holding down the casing you'll see a radiator looking thing. This is your heater core. it'll be held in by two metal straps. once you undo the metal straps and have disconnected the heater core hoses from the outside you can simply pull the heater core out.

Couple things to take note of. You'll have to open your glove box and take out the 4 screws holding that in (the 9/32" ones I mentioned) and drop it down to gain access to the rest of your 7/32" screws holding the casing in. Also note that the casing is sealed. Meaning it has a little rubber gasket in there that makes it airtight. Which may also be stuck when you try to remove the casing. Get a small flat object to pry with if your 100% positive you've gotten all the screws out. and it should pop off reletivly easily. (I used a butter knife)

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Step 4

Grab your new heater core and hose clamps. Take your new core and place it through the holes in the firewall. Now I persoanly go out and hook up my Hoses at this stage I'm not sure if clamping down the 2 straps yet holding the heatercore on would effect anything or not. I just hate laying on my back on the floorboard and then having to get up and out over and over. Once the hoses are hooked up get back under the consol replace the straps and put the seal back in the cover and put everything back together.

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Step 5

Here's an example of something you want to avoid at all cost. This is your Heater Core casing (this one is out of my 94' RS) all cracked. if your casing is cracked your not sealing the core and your not going to get much heat. And should you have another core failure your going to end up pretty soaked. So do your best not to crack it. If you do crack it I would strongly suggest replaceing it with a good casing. But if all else fails Duct Tape does work in this situation. (Consider it a temp fix though)

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Step 6

Once everything is back together refill your coolant and burp the system to get rid of any air bubbles. You're all set to go. See, now wasn't that simple?

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