You bought a new hooptie in the summer, and everything was going great. It starts first time, the temperature needle stays in the middle, and it even came with four decent tires. Only, there’s a problem. It’s winter, now, and you’ve noticed the heater’s out. You may have even noticed a dribble of coolant on your floorboard. Your mechanic buddy tells you it’s the heater core. “I’ll fix it myself, how bad could it be?” you say with confidence. Your wrenching friends look back at you with pained expressions, shaking their heads in dismay.
Wrenching on your own car isn’t always bad. It’s often a great way to learn things and save money. Changing your engine oil is an easy enough job, for example. From there, you might step up to more difficult task like replacing your shifter bushings or changing a water pump. Unless you’re an all-out masochist, though, there’s one job you probably want to avoid—swapping out a heater core.
A heater core is not expensive or complex — it’s basically just a small radiator under your dash with an inlet and outlet pipe. And yet, changing one out requires more work and more hassle than almost any other typical job on a modern automobile. Let’s explore why this cursed job is such a monumental pain in the ass.
Heater What Now?
A heater core is the heat exchanger tasked with turning engine heat into cabin heat to warm you and your passengers. Typically, it consists of two end tanks connected by a bunch of straight tubes that have lots of fins attached. Engine coolant flows through one end tank, then through the tubes, giving off heat to the air that passes through the fins, picking up heat to warm up the cabin. (The additional surface area of the fins attached to the tubes help the air pick up heat). In order to get that air through the heater core and into the cabin, a blower fan forces air through the heater core to warm it up and keep you nice and toasty.
Fundamentally, the heater core works exactly the same way as the radiator in the front of the engine bay. The difference is that it’s much smaller, and it’s not intended to actually cool the engine to any major degree (though it can help as a trick if you’re starting to overheat a bit). It’s just using the waste heat in the engine coolant as a convenient way to warm up the interior of your car.
You might like to ignore a busted heater core, but depending on the failure, you might not have much of a choice. If the heater core is leaking, your engine will be losing coolant—potentially quite quickly. If you get too low on coolant, you might end up overheating your engine. What’s worse is that the coolant will most likely be dripping down inside the cabin, underneath the dash and onto the carpet/floor mat. Less troublesome but still far from ideal is when the heater core clogs. Without coolant flowing through it, you don’t get any heat transfer to keep you warm. It’s troublesome, but less likely to pose a risk to your engine and interior.
Since they’re so simple, heater cores are actually pretty cheap, parts wise. They’re just small radiators, after all. You can find them for under $200 for most common models. They typically have one inlet and one outlet, so hooking them up is easy. So what is it that makes this job so hard?
Access Is Everything
The problem with heater cores is that they tend to live in an awful, inaccessible location deep under the dashboard. As a bonus, the inlet and outlet pipes typically feed through the firewall and into the engine bay. They usually end up tucked somewhere off to the side of the engine, buried so deep that you have to pull apart half the car to get to them.
Take a car like the BMW 3 Series—say, the E90 generation. Head over to the Bimmerpost forums, and you’ll find a helpful DIY guide explaining how to do the job. “Please allow for an entire weekend to get this done, even with a helper,” writes zigsman, noting the job took them a full 16 hours of wrenching to complete. Meanwhile, DIY Salvage Guy on YouTube says you can expect to spend 20 hours doing the work, or spend $3,000 to get a shop to do it.
Just reading the tools list, you get an idea of how bad this job can be. Beyond the usual screwdrivers and socket set, you’ll also need a whole set of air conditioner maintenance tools. We’re talking gauges, tanks, fresh refrigerant, the whole shebang. Why? Well, in this case, since the heater core pipes are a particularly inaccessible part of the engine bay, you have to remove parts of the AC system to get to them. This means that purging the air conditioner is just one part of this job, and you have to refill it—accurately!—when you’re finished, too. Recharging the AC is an ugly job for a first-time DIYer, and needing all those extra tools just adds to the cost and frustration of the job.
Other headaches include having to pull apart the steering—and don’t let the wheel rotate, or you’ll wreck the clock spring and add a whole other painful job to your list. Assuming you can tackle all that, you also have to pull apart the entire dashboard to handle the interior side of things, too. Assuming you can disassemble and reassemble everything without destroying any of the fragile plastic parts in the BMW engine bay, you might have a shot at pulling this off. Just don’t forget to have the BMW service software on hand to clear any frustrating codes that pop up when you’re done.
BMWs aren’t exactly known for being easy to work on, but the story is much the same elsewhere. Try swapping a heater core on a Chevy Malibu, as covered by Mississippi Wrenches. You’ll wind up doing the same amount of work. “I usually don’t say a lot of jobs are hard, but take my word on this one here—this job is not for the faint of heart,” says the exhausted wrencher. There’s no getting around it—you’ll need to pull the whole dash to get to where the heater core lives, deep under the dash. In the engine bay, it’s the same story—there’s a bunch of AC lines and other stuff that make it hard to get to the hoses on the hater core. Even when the plastic heater box was pulled out of the car, it had to be drilled in multiple places to pop it open and free the core for replacement.
Replacing a heater core is a lot of work, but it’s also ugly work. Uncomfortable, back-twisting, knuckle-busting work. Compare it to another job, like replacing a head gasket. That can be time consuming, but for most of the job, you’re attacking the engine from above. You’re unbolting things off the top of the engine, pulling the head, and then putting it all back together. Time consuming, but straightforward.
Doing a heater core is much worse. Have you ever had to contort yourself upside down into the footwell of a car to reach bolts under the dash? I promise you, it’s eight times worse than it sounds. Now picture doing that for hours on end as you pull the dash apart, piece by piece.
Meanwhile, unhooking the pipes on the firewall is sure to strip plenty of skin off and leave you raging as you drop your pliers into the depths for the fifteenth time.
Oh, and at the end of this job? You’re left with a bunch of broken plastic fasteners and trims that will never go back together the same way again. Heater cores typically fail on older cars with weaker plastics. You know the kind. Parts that have been baked in the sun for years and crumble if you look at them the wrong way. You’ll be lucky to have only cracked two or three major dashboard components before you’ve even figured out how to get the infotainment system out of the way.
When the customer asks why a 200 dollar heater core costs so much to put in
byu/Pitiful_Celebration inJustrolledintotheshop
Not every car is as bad as the examples above. If you’ve got something simpler, the job can be quicker with less fuss. You’re still likely gonna have to pull a whole dash apart. Older cars tend to have emptier engines bays with easier access, though. That might mean you don’t have to tangle with AC lines or a forest of sensors and wiring. Maybe.
Say you’ve got something like a TJ Jeep Wrangler, for example. Forum users quote prices around $200-ish in parts and 8 to 10 hours labor for getting the job done by an independent shop. If you get a quote for $1,000, that’s not a bad thing—that’s actually pretty good. On an NA Mazda Miata, you can do the job without even pulling the dash, as shown by GearHeads on YouTube. Even better, the coolant lines going to the firewall are really easy to get to, mounted nice and high in the engine bay. You might even get a sub-$1000 quote for a shop to do it, based on reports from owners on Reddit.
[Ed Note: Some vehicles, like old full-size Jeeps, have heater cores mounted to the firewall in the engine bay. These are a godsend:
Look at how easy that would be to replace! You don’t even have to touch the dash! -DT]
An old Chevy Tri-Five might have been a bit easier to swap a heater core on, as this diagram demonstrates. Plenty of room in that engine bay.https://www.youtube.com/watch?v=bFDkCjR1JqM
When it comes to awful heater cores, though, the title goes to the fifth-generation Chevrolet Camaro. Why? Before you can remove the dashboard to get to the core, first you must remove the windscreen! All because of two bolts in the dashboard that sit right at the base of the windshield. I wish I were making this up.
I wouldn’t be honest if I didn’t tell you there is technically a way around it. According to the Camaro5 forums, It just involves hacking away at some bolts with a Dremel cutoff wheel, a prybar, and a good chance of breaking the windscreen if you make a mistake. Still, the official GM instructions call for windshield removal.
heater cores you say? how about one on a 2011 camaro? (and yes the windshield has to be removed to remove the dash)
byu/zackdman inJustrolledintotheshop
Cheating
When a heater core replacement becomes necessary, it can be a killer for an old car. Few people want to invest $1,000 or more in fixing an old beater, after all. If you live in a cold climate and the heater is a must have, you’re out of luck at this point.
However, if you’re willing to forego the heater, a simple trick might save you. If your heater core is leaking coolant under the dash, you can simply choose to bypass it instead. You’ll still need to be able to get at the coolant hoses in the engine bay, but you won’t have to mess around with the dashboard at all.
This technique is called “bypassing” the heater core, or “looping the lines.” Basically, all you do is you disconnect the inlet and outlet hoses that go to the heater core. You then connect them to each other with a small U-pipe or other fitting. Alternatively, you remove the original hoses, and run a single new hoes from the heater supply port on the engine back to the return port. Either way, instead of the coolant flowing into the heater core and back out, you bypass it entirely. Generally, this won’t cause any harm and can keep your car running and roadworthy when it would otherwise have a serious coolant leak.
This fix is essentially free and it’s also not very time consuming. It also minimizes the chance of you breaking twelve other things on your car while you’re wrestling to free a filthy, leaking heater core.
Bad Times
Some automotive repair jobs are difficult because they require specialized knowledge or tools. Heater core replacement is difficult because it requires a ton of annoying intermediate steps just to get access to the part you actually want to work on. The more parts you touch on a job, the more likely you are to break something along the way, too.
Heater core replacement is perhaps the one wrenching job where it’s not cool to ask your buddies to come round and help. Friends don’t put friends through that kind of pain, even though a second pair of hands is extremely helpful. If your car has a busted heater core and you want it gone, I understand you. If your car has a busted heater core and you’re going to pay someone else to fix it, I understand you. If you choose to just wreck it instead, I get it, I do. Whatever happened, get yourself a cold beverage and try and put it behind you. Heater cores just suck.
Image credits: Lewin Day, Chris Vaughn via YouTube screenshot, Mississippi Wrenches via YouTube screenshot, DIY Salvage Guy via YouTube screenshot, eBay, Amazon, brosolution via YouTube screenshot, Chevrolet, Amazon
The ‘69 C10 I drove in college had a heater core that was entirely accessed from the engine bay. Replacement was an hour tops. Not, mind you, that the heater ever actually worked.
My 1st generation Durango. Miserable job. So many broken fasteners, cracking brittle dash, buried down deep. After everything was back together, the gear selector indicator didn’t work and squeaks everywhere. But the heat was wonderful for winter!
Yep – the one car repair that is seared into my memory was helping my father with a heater core replacement on a 1989 Crown Vic. Dash parts everywhere, but somehow we got it back together with very few missing fasteners. What a PITA…
Yep. Never again. My nemesis was a “free” 1998 Isuzu Hombre. The plug wires were a pain, the dash plastic was super brittle, and the carpet was super gross. The loss of death was the cracked heater core, and due to needing to defrost the windshield bypassing wasn’t viable. That job took more work than overhauling the transmission and replacing the clutch. My buddy who helped me told me not to do it; and I’m amazed in hindsight he remained my friend.
Having done one, once, I’d rather single handedly rebuild an automatic transmission out doors in January. If it’s a toy car, maybe I’d do it again bc I can take my time on the job. But for a daily, where’s my credit card.
Heater core replacement may be easy on a Miata, but there’s not enough room back there to snake the engine harness through the firewall without removing the dash.
My personal tip – One Quart Freezer Bags.
Remove a part, put all the hardware removed in that step in a freezer bag and then tape the bag to the part with masking tape. Makes it a lot easier if it’s a project car that you may be working on over time instead of all-at once.
Had to do the heater core replacement in my Sunbird. I always had a faint antifreeze smell when I turned on the heat, so I knew it was time before a catastrophe happened. It was such a relief that we didn’t have to pull the dash! The heater core itself had the smallest of leaks/cracks at the tip-top and looked like it had for a long time.
I must be the weird one.
I find replacing the heater core deeply satisfying. It is an easy way to learn about a car, and I get the satisfaction of awesome heat.
Although, I have only dealt with cars that are from the 80s and older… That is a huge caveat.
It’s really too bad cars had to end up the way they did. Just being unnecessarily complex machines that no one but an expert can fix. I refuse to believe 1. They couldn’t have kept them easily serviceable 2. It wasn’t on purpose.
Heater core is a basic item with no moving parts. The manufacturer can be pretty confident the heater core will last the full warranty period, which is all they are concerned with service-wise.
They’re not intentionally making replacement difficult, but it’s definitely not a priority to make it easier.
I just did the evaporator and heater cores on my Ford Focus (evap core is a known weakspot on this model, and had corroded until it leaked). Console out, seats out, dash out, HVAC box out. Threw in a new blower motor and resistor while I was at it. UGH.
I think you failed to give GearHeads proper image credits as I think your “The Typical Service Position” came from their Miata video here:
https://youtu.be/bFDkCjR1JqM?si=DDjrvlKJYs-Qvhfn&t=1264
Nevermind, you did it in-line rather than at the end. The Editor’s note kinda broke that up a bit so I missed it as I was scrolling.
I remember happening in on a shop one day working on a Fox-body Mustang. The dash, seats and center console were out of it. I said, “jeez, what’re you doing to this poor car?” The answer was heater core. I don’t remember the exact order, but apparently to get the dash out, you had to remove the console, but to do that you had to remove the seats. Or some such. I’ve never seen a car so apart that wasn’t having a full restoration done.
I just did the one in the Travelall, which is directly under the glove box on the passenger firewall. Three bolts and two hoses, and it came right off.
I hope to never have to touch the ones in my Hondas.
Recharging the AC is an ugly job for a first-time DIYer, and needing all those extra tools just adds to the cost and frustration of the job.
Most if not all those tools can be borrowed from Autozone. And recharging really is not hard nor expensive. I replaced the Schader valves in my car in my first A/C job a few months ago and after that it was just to hook up the manifold and vacuum pump, pull a vacuum, close the pump valve to make sure there were no other leaks, then replace the pump with a can of freon, purge the Freon line, open the valve and start up the car to get the pump going, replace the drained can with a fresh can, pump that into the line, check the pressures against the recommended chart to verify all was good and the job was done.
She still blows cold.
I have not had heat in my Matrix for over a decade, I think. It broke on the way home from Vegas (it was hot out and the water temp was getting high, so naturally…).
I checked instructions for replacement, and there were 170 steps. No thanks.
Only a few days in winter early morning when there is frost on the windows that won’t go away until noon. I’m in SoCal, so not a big deal. I also have my wife’s car if she’ss not busy with it.
It has got to be the very first thing installed on the car. Because of that, it should be the most durable thing on the car.
Air conditioner evaporator are,even worse, just a inaccessible and you have to deal with refrigerant. Here’s the Car Wizard https://youtu.be/Tb4yPzdZ-AI?si=HePpUMXHwInecuZ2
I’ve done one heater core in college on a 1980 Subaru and I would be happy to never do one again. It’s a lot easier in equipment because if there is a heater it’s right there with maybe two pieces of trim.
I recently replaced the blower fan in my VW T3, The matrix and fan are both in the same housing, This requires dashboard removal and then you find the housing is in fact glued together, So you have to tease it apart while carefully breaking all the glue joints. After all that it’s quite easy… I stuck mine back together with silicon to make disassembly easier next time.
I think heater core replacement is why PRNDL is standard… I replaced mine on the Olds Achieva and got the car “functional” and took the next 18 months (or more – the memory is hazy on this) to get everything back in place. Since it wasn’t just removing the dash, but also removing the center console, Whenever I shifted out of Park – I would constantly have to remember PRNDL. And when I lost track – go back to P and start all over again.
I once spent a few weeks driving my old Chrysler Pacifica without a center console shifter while I waited for the replacement shifter to arrive. A small plastic piece deep inside the original one has broken off, rendering the entire thing stuck in P. So I simply disconnected the shift cable from the console shifter and pushed/pulled through the detents to get to the right spot. It was jank as hell but also made the car much harder to steal. (Not that anyone in their right or wrong mind would bother stealing such a POS.)
I had to use my heater in my Solara to the other day and I noticed I had to turn up the heat pretty high… My immediate thought was the dreaded heater core, but I don’t have a frame of reference since I only use the heater a few months out of the year.
Thankfully, the worst of it involves removing the dash, which apparently isn’t too terrible on that car. But supposedly you can do it but just removing the lower dash. Either way, I do have to remove the A/C condenser which means a trip to the shop to have my A/C discharged.
On the plus side, it doesn’t appear near as bad as the BMW in this example. And as an added bonus my dash is in the starting stages of developing cracks (a common issue for this car) so I’d definitely use this as a good reason to swap in a new dash panel.
I’m needing to do this job on my Saab 900 here shortly (wet driver’s floormat, cabin smells like coolant when heater is on…makes sense) and I’m…dreading it. Maybe I just deal with the drip.
Yes, a major pain. The last time I replaced one was ages ago on a very simple to repair car. It was so long ago that, to my recollection, the only color of coolant in American cars was green. 🙂
A couple of comments: 1) as much as the corporate Service & Parts operations of most OEMs are involved in the very early stages of vehicle design, DFS&R (Design For Serviceability & Repair) is many times compromised due to packaging and impact constraints, cost, PIA (Purchased In Assembly) sub-systems and systems like complete instrument panels from Tier 1 & 2 suppliers, etc.; 2) before a vehicle’s carpet even begins to get damp from a seeping heater core, the early warning sign is that the inside of the windshield will begin to “fog” up and you can taste the coolant in the air you’re breathing inside the vehicle.
When I bought my Datsun, the heater core was bypassed, and the AC compressor belt was missing. At first I didn’t think much of it.
When I disassembled the car, I realized the heater core and AC evaporator are at the very heart of the dash and would be a pain to get to again after reassembly, so I overhauled everything.
I had both radiators pressure tested by a reputable shop, I disassembled and cleaned every bit. Got rid of rust and repainted all the brackets and parts. I scavenged another car for heat control bits and bobs. I changed every single hose under the dash. Double checked every single clamp …
And yet, I didn’t connect the heater back. I haven’t had the courage to do so. I am so afraid to have a leak under the dash and have to pull everything apart again. I once spent 2 hours contorted under a friend’s 260Z dash for a small leak and that was brutal.
I always picture assembly lines where the first thing that happens is somebody hangs a heater core on a hook and the vehicle is built around it
Did my 98 F150 back in 2009, found step by step instructions that someone posted online with several short cuts. Basically had to pull the entire dashboard. In the end it took me a full day, some cut knuckles and three left over screws.
Precisely why my ’81 Z28 hasn’t had working heat since sometime in, I suspect, the ’80s when it failed on my Uncle. He lived in LA so it wasn’t necessary…and thus it was bypassed.
It’s still bypassed. Probably will remain bypassed.