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
I’ve seen some people take the perspective of, the manufacturer put the whole dash assembly into the car all as one unit, maybe it would be better to try to take it all out as one unit rather than just trying to access the one part. And it turned out it was better, by hours. No idea how helpful that is in real life.
I had this situation happen just last year with a new-to-me 94 Toyota HiAce. One of the things I love about that truck is that the dash comes off in about a half hour with a screwdriver and a 10mm socket (well okay, maybe a 13mm too) and so the whole thing was pretty fast. As an old fart I appreciate this, given that I’m not as bendy as I used to be
This very issue has stopped me from getting one of my dream cars – a W140 or C140 – so many times. It’s a really common failure on that chassis, and book time is 26 hours.
The dude doing the heater core in a 2010 Malibu—just why? Send it to the scrap heap and get another one.
88 F-250 has a very easy heater core to replace. It’s behind the glovebox and you just have to tilt the glovebox down all the way past the stops, unclamp the 2 hoses in the engine bay and slide it out.
On the other hand, on my 86 300ZX you had to pull the entire dash to get it out, but at least you didn’t have to purge the AC system.
Shoutouts to the 79-91 LTD Crown Victorias / Grand Marquis where you can just barely get the heater box out from under the dashboard by loosening the front dash screws on the sides and pivoting the whole thing up slightly.
I used to think the RWD G-Bodies were terrible to work on, till I tried a Panther. Utter trash.
I love my ’89 panther but sometimes it baffles me this car came from the “Quality is Job #1” era of Ford.
Similarly the AC Evaporator tends to be just as much of a PITA as the heater core, as they tend to be neighbors up under the dash. Just instead of messing with coolant lines from the radiator, you get to deal with the AC supply lines. Had the evaporator go out on my truck and while I could sort of get by without AC (not super fun being a black truck with black interior in 90 degree days) it was a pain not having proper defrost for the windshield.
It ended up being the straw that broke the camel’s back and as the truck was worth about $1500 and I wasn’t going to do 20 hours of labor, so it was going to cost me about $1500 to get fixed, that was that for said truck. (That and it was starting to rust out along the bed wheel tubs, and the doors, and the transfer case would get stuck in 4HI).
Why take out the heater core when you can install a propane-powered space heater? It’s a simple, elegant solution, and really shows the high caliber of vehicle it is installed in.
We all know that propane tanks are safe, just ask any Toyota Tacoma owner transporting one while lighting a cigarette!
Heater core locations and trying to replace a relief valve under a reduction gear set on my ship is why I look at engineers with a double helping of distrust and a bucket of simmering hatred.
Heater cores I have replaced, or thought about replacing:
’99 Ford Crown Victoria – yuck, miserable. Nope. (though while you’re in there , you can replace the vent tube behind the radio so a full double-din head unit will fit – whole-ass dash has to come out). I do not understand the affection for the Panther platform Fords. They’re a 3/4 scale late ’60s car with build tolerances to match and stupid fiddly wiring and stupid, stupid accessibility decisions for just awful serviceability.
’84 Cutlass Supreme – did this in about a half day in the dorm parking lot. Not bad at all. I learned on the G-body Monte Carlo I pulled the used replacement out of. Accessible in the engine bay.
’82 Fox Body Granada – didn’t actually do the core, but I bypassed it in the high school parking lot to get home. Turns out this is a simple job, too – it just kinda slides out.
’90 Volvo 740 Turbo – core wasn’t too bad, it’s Harrison HVAC, just like the G-body, but packaged a little differently. The AC Evaporator was a right bastard that required a lot of disassembly though. Or maybe it was the other way around. Not my favorite, not the worst.
’01 Volvo S60 – easy peasy. Didn’t change it, wasn’t the core, but the o-rings. These are DELIGHTFUL. They slide in/out like a cassette and the coolant connections are snap-tight affairs. Well thought out.
’83 Volvo 240 – Misery, but I was young and eager. Replaced the entire climate box that the car is, indeed, built around. I had one of the very rare ’83 240s in North America without A/C, and big dreams of installing it, so I popped in a central unit with evaporator and expansion valve in place. And a good heater motor. Wired up a heater motor switch and relay, too, to extend the life of that item, which ALWAYS dies and is buried *inside* the box.
P2 Volvos are easy, the hardest part is actually removing the brake light switch without breaking it. BTDT on my ’04 V70. A mostly hateful car, but at least that job was easy. That it decided to shit the bed while I was on my way to the airport and already running late for my flight was not a ton of fun though.
Hey Kevin!
It’s a good thing they designed the P2s to be serviced, because they sure do need a lot of it.
If you want to spend BMW/Merc money on keeping a pretty but clumsy car going, they’re a great choice.
LOL – hi Dan! I totally missed that was you!
I could not possibly agree more – except in my direct experience my P2 cost *multiples* of what any of my BMWs and Mercedes have cost to run. For a car that was a lead sled to drive at the end of the day. Never again. Shame though, they are such pretty cars, and useful too.
I hated fixing these on old 60s-70s junk in the the day. I remember a friend saying that even the connectors were like one way screws on some heater core box on something they worked on.
Part of how I define a “good car” is, that it is designed to be fixable when parts fail. I parted out a ’94 Trans Am and it took hours just to get to the heater core. Not good car. Weeks later the core in my daughter’s Saturn failed and after pondering just slitting my wrists in the bathtub instead, I went at it. An hour for the whole job. Good car.
I’ve lucked out with the heater cores I’ve done over the years. With a bit of practice you can get the dash out and get to the heater core in an A2 Volkswagen in about a half hour. The heater core replacement on my mid 60s Chevy pickup with the standard Thrift Air heater was done completely under the hood. It helped that the engine was out at the time, but getting the core out of my nephew’s Volvo 850 wasn’t horrible, though the plumbing was a bit fiddily.
The one that I’m glad I didn’t have to do was my Volvo 240 wagon, which I understand requires disassembling the entire dash and firewall to get to.
I don’t know if this was intentional, but “hater core” is perfect here. If it was a mistake, please leave it alone.
I changed the evaporator in my Suburban in 30 minutes with an orbital saw and foil tape.
I thought the heater core in my wife’s ’95 Escort sucked to replace. Parts of the heater-control unit basically disintegrated upon disassembly and now I have to manually set the under-dash air-diverters on each side to match the season it’s being driven in. Still, nothing compared to that BMW above.

Meanwhile, it was about a 20 minute job in the ’89 Brougham I had. Everything was easily accessible from the firewall.
I have done many heater cores, and I recall some YouTuber (Demuro maybe?) looking at an older GM truck and mocking the fact that you could see the heater core box beneath that dash down by the feet. I immediately took offense to the comment, because I have done more than one heater core on those older GM trucks and the ability to just slide off the box and swap the core relatively quickly and painlessly is far and away worth the lack of aesthetics.
I know autopians are in the minority, but I’m always amazed at how the majority of buyers want their vehicles to seemingly do everything possible to NOT remind them they’re vehicles.
People seem to want their conveyances to feel like some kind of magic device, not the intricate machine they actually are.
Ugh… The car-as-appliance. No, thank you.
Heater core in my 99 XJ had a minor leak when I bought it. Used stop leak and that indeed stopped the leak but also most of the heat, as I thought it might. It’s mostly a summer beach vehicle and we’re parking it this winter but would like to use it in next winter.
Reluctant to tackle that heater core job in a Jeep with 250k miles. I live in central New England and my real concern is not comfort but having the windshield ice up. Anyone ever try one of those 12V defroster/heaters? They’re only 150 – 200 W and get plenty of bad reviews but maybe it’s enough to keep the windshield clear?
I had a friend with a similar situation while living in Minneapolis. His 12V heater couldn’t move enough hot hair to clear the windshield of the condensation of his breath except in a 6″x6″ spot directly ahead of the heater. His response was to use a balaclava to capture the moisture from his mouth to keep the windows from fogging up. Not ideal, to say the least. We (I, really) ended up replacing his heater core when it was -10 outside, which sucked.
I tried a 12v heater in my 70 commando in Minneapolis in the 1990s and it was worthless. I would just ware a parka and ice scrape the inside of my windshield as needed.
I tried a 12v heater in my 70 commando in Minneapolis in the 1990s and it was worthless. I would just ware a parka and ice scrape the inside of my windshield as needed.
I tried one in a Mercedes with a faulty vent actuator. It was completely worthless and also seemed rather dangerous.
I’d try putting an egg (egg white) in the radiator, or a similar concoction from the auto parts store, before trying to tackle a heater core.
It’s incredibly frustrating, because similar cars of similar eras can be wildly different. My 95 Chevy? Few bolts below the dash, drops right out. My 91 Ford? Same, just remove the glovebox door. My BIL’s 99 Ram? REMOVE THE ENTIRE CRUMBLING CHRYSLER DASH AND PRAY IT GOES BACK TOGETHER.
They could be designed to be serviceable. But manufacturers are like ¯\_(ツ)_/¯
I think part of the problem is that HVAC boxes are designed by a supplier with little consideration about the layout of the rest of the dash.
I had to get into the HVAC box of my WJ Grand Cherokee on three occasions. Everything has to come out, but the main structure of the dash is one piece of cast aluminum and other than being large, is fairly easy to take out.
Yeah I’ve noticed that on newer rigs especially. The current (or previous?, donno, one of the egg shaped ones) Escape requires removing the goddamn drivers door, the dash, and probably every single interior bit to get access to the heater core, as it is one giant unit with the blower motor, blend doors, heater core, and whatnot all in one.
Absolute worst one I’ve ever had to do was a Mercury Sable. Must be a Ford thing.
My old Toyota’s heater core started leaking after 40 years, by that time there’s no replacement and I just did the bypass. I doubt the dash could’ve been taken apart anyway, it was already cracked in so many places.
First one I did was in one of my 80s Subarus. Went pretty well—except this was before I had a digital camera, so I never did quite get all the various ducts & wire harnesses back correctly, so dash was wonky until I retired the car.
2nd was a late 80s Toyota truck—and I had a camera by then. Tedious, but all went well.
have not done another, and likely will avoid doing so. Life is too damn short to be hating it.
A friend did his own heater core in a Mitsu Mirage. The job went as expected (it took all day and looked like the pics above), but went well! But anytime he gets even a squeak out of the dash, he blames that core.
If I heard a squeak in the dash, I’d blame the Mitsubishi Mirage being…well… a Mirage.
Just did the ’14 Passat TDI. It was easy – it slips in and out like a cartridge, six hour job. It’s like they knew it would clog due to the design and decided to throw us a bone and at least make it easy to swap.
When a six hour job is “easy,” you know a typical heater core repair is awful.
Or that working on a VW is.
But why though? Why are they almost universally in a horrible location? There are lots of things under the dash that can be replaced or repaired with the dashboard in. I always wondered why there can’t just be an access panel like there is for some cabin air filters. I could understand having to remove the glovebox, lower dash, maybe some ancillary equipment, but the whole dashboard? What is it about the requirements of a heater core that makes engineers say “this must be installed in a terrible location, there’s no way around it”.
Or why not just put in an electric heater.
Electric heaters typically draw an incredible amount of power. If I’m using the watt calculator thingy right, a typical space heater (1250ish watts) would draw 110 amps in a 12 volt system. My alternator is only capable of 70 amps in one of my cars. In my Volt, the electric heater will kill my range from 10-20 percent depending on temp.
You probably don’t need 1250 watts to heat an area the size of a car though. That’s more than enough to keep the 14x8x6.5′ interior volume of my trailer toasty warm.
Not that it invalidates your point. That’s why they’re putting heat pumps in EVs these days. It’s just not quite as bad as those numbers might make it sound.
Totally agree, was really just trying to make a point with a familiar point of reference. Although, my Volt’s heater will draw more than 2 kw quite often when running. Hard to compare though, as that is heating up coolant for the batteries as well as the passenger compartment.
I’m assuming 12v would just suck for that.
Might work in Miami. Won’t work in Minneapolis.
What can I say, VAG has beaten me into submission 🙂 There are four lights!!!
*THIS* It adds so little to make the heater core readily swappable. I had a hooptie that needed a heater core. I could have torn the dash apart and then the heater box, but I just cut a slot in the side of the heater/blower box and slid the thing out in a couple hours. I put my homemade access door back in with silicone sealant.