There’s an old (Lynyrd Skynryd, I think) lyric that goes, can’t you smell that smell? Well, I just smelled it.
The smell of a leaking heater core. Accompanied by the sight – of greasy steam rising from the passenger side floorboard, which quickly becomes a film that coated the inside side of the windshield and side glass. Soon, you won’t be able to see where you’re going anymore – unless you use a rag or even just your hand to clear a hole.
A leaking heater core is among the most unpleasant automotive failures – especially when it happens in winter. Few earthly delights can compare with having to drive in freezing weather with both windows down – to vent the steam – while you nervously eye the rising temperature gauge (due to hemorrhaging coolant) and hope you’ll make it home.
In case you don’t know why, I’ll explain:
The heater core is basically a small radiator that’s buried deep inside the dashboard. Warm engine coolant flows through the heater core to keep the car’s interior warm when it’s cold outside. It’s free heat, too – at least in the sense that it does not cost you anything extra to keep warm. The system simply makes use of the heat generated by the engine to keep you warm. In a battery powered device – that is, an electric vehicle – there is no engine and so no heat except that which is generated by burning electricity. That depletes the charge available to keep the device moving, which presents a rather interesting Catch 22 in the wintertime: Do you want to make it where you’re headed? Or do you want to stay warm?
The downside to free heat is that just like the radiator that cools your engine, the heater core that keeps you warm when it’s cold out eventually springs a leak. This happens due to metal (or plastic) fatigue, the effects of corrosion and so on. It is an inevitability, too. Keep a vehicle – any vehicle – long enough and you will, one day, smell that smell.
That day arrived the other day. My Nissan pick-up is 23 years old, so I wasn’t surprised when I smelled that smell. Just not exactly ready to deal with it. No one is ever ready to deal with a leaking heater core. It just happens one day and then you have to deal with it.
The good news is, it’s easy to deal with – in the sense that you won’t be immobilized by a leaking heater core. If you’ve still got a long way to go when you first smell that smell, the thing to do as soon as you can is to find an auto parts store and park. Then pop the hood and let the engine cool down. After about 30 minutes, you ought to be able to loosen (don’t entirely remove) the radiator cap, to release the pressure within the system. Use rag over the cap to protect your hand from hot steam/coolant.
Now look around for the two smaller diameter hoses that run from the engine to the firewall, usually on the passenger side. These are the hoses that circulate the warm engine coolant through the heater core. What you’ll want to do is disconnect them from the fittings and then splice them together – using an appropriate piece of pipe the correct diameter to fit the two together. The auto parts store will have what you need – including some hose clamps to tighten up the spliced line and fresh coolant to top off what leaked into the passenger compartment (your front seat passenger side’s carpet is probably wet and – later on, when you get home – you will want to dry it out to get rid of the smell and to avoid getting rusty floorpans).
Now you can drive wherever you need to go – even if it’s across the country. But you won’t have any heat.
To get the heat back, you will have to replace the leaking heater core with a new one that doesn’t leak. The bad news is that while a new heater core is – generally – not an expensive part (mine cost about $60) the labor to have it installed is. Because it generally requires extensive labor to get at the old, leaking core. As in major disassembly of the vehicle’s dashboard. Because the heater core is one of the first components installed during vehicle assembly; everything else comes after – and so in the way of removal.
It is often a job that is beyond the skill – and the will – of the the vehicle’s owner.
In the case of my old truck, it’s not all that bad. One of the reasons I cling to my old truck being the fact that it was designed in such a way as to make most repairs relatively easy. To get to the heater core, remove the glovebox – six screws – which exposes the heater box. Then disconnect the AC lines that plumb into the box (I have a mechanic friend who is a “certified” AC tech and so I can use his machine to save the refrigerant rather than lose it to the air) and remove the heater box. Now you can get at the heater core, which slides in and out like a cartridge-style cabin filter.
So that’s what I’ll be doing over the weekend.
For now, though, I’m re-experiencing the days when I drove an old Beetle that didn’t have a heater core.
Or heat, either!
. . .
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Oh, I feel for you. Such a simple fix but for the lack of access. I just did a starter on a BMW X3. It was a $100 part held in by 2 bolts, but it’s impossible to get to it without removing the entire intake system, including the manifold. What would have been a 30 minute repair with access was about a 12-hour ordeal.
I’ll reiterate what others have said, take many pictures along the way. The memory fades quickly and you’ll need them.
In college in the 70’s I replaced my GF’s heater core in her Rambler. I had limited mechanicals, mostly working on motorcycles. It wasn’t difficult to do as lying on my back in the passenger floorboard area at that age wasn’t a big deal. Now it would be unbearable pain to repeat it.
Eric,
I believe a similar problem eventually led to my Chevy overheating.
See, my heater core became clogged as there was a lot of rust in my cooling system. To try and alleviate the problem, when I changed out the heater core, which was a lot easier than I hear of many vehicles, I changed the rest of the cooling system, too, meaning the hoses, radiator etc.
One thing I didn’t change, as it didn’t come with the radiator, was the radiator cap. I used the old one because I thought that would be fine.
But it was not fine.
It was one of those with the built-in relief valve, which is what I believe malfunctioned, leaking all of my coolant and overheating the truck.
Lesson learned: Always replace the radiator cap, and probably best to just get the simple type, sans relief valve.
The downsized late 70s GMs actually had a humane design for the HVAC. The heater core, ac core, and fan all accessed from the top of a box in the passenger side corner under hood. I did the heater core twice and the fan three times (cheap ass replacement fans) in the 21 years I owned “Old Yeller” the 1979 Pontiac Gran Prix. The fan was so simple, right out in the open took longer to find my 1/4 drive ratchet than to pull the fan assembly.
Contrast to the heater fan in the 1971 Nova. What a PITA. Had to pull the RH fender liner just to see it, same with the heater core replacement.
You can double/triple the life of a Heater Core by operating the heater once a month or so over summer for about five minutes each time. This will flush out any crap and refill the core so no air gaps exist. Always use distilled water if possible when topping off the coolant system…
Yes and make sure use the correct coolant for your year make and model. Endorse your use of distilled water ONLY as well!
Hopefully it will be easy for your truck. The square body chevys only had 3 nuts to get the heater box out so that plus removing the control rods and glove box and you’re all in. I have a 2014 grand cherokee—-oh boy. I dont know where to start with that one. I hear S10 puckups and blazers were also terrible for this job.
Off topic: Motortrend made a short documentary about the American V8 engine. Interviews with real car guys praising old school and modern V8s and predicting they are not dead, they’ll come back.
Highly recommended:
https://www.youtube.com/watch?v=AWL-k2J24vY
Yep! That’s happened to me twice over the years. And both times in winter when it can become a hassle when you can’t feel your fingers.
Over 30 years ago I replaced the heater core in my Monte Carlo. It’s one of those cars where everything in front of the driver has to come out to do the heater core. A learning experience to be sure but not exactly fun.
Sadly on newer cars the blend doors and actuators fail occasionally engendering the same disassembly for repair but a site called https://www.heatertreater.net/ has a solution for that.
Take lots of pictures cause it’s a sucky job to do twice. Also buy the best part you can afford because you don’t want to do it twice and check all them linkages while it’s apart in case they are about to fail.
“ For now, though, I’m re-experiencing the days when I drove an old Beetle that didn’t have a heater core.
Or heat, either!”
Eric . . . . Come on Brother . . . I expect more honesty from you.
I am a HUGE fan of all things air cooled. Beetles, Busses, Porsche’s.
Air cooled engines have sufficient heat. This mythology that Aircooled lacks heat is due to so many air cooled vehicles having been neglected and completely rusted out that the heat exchangers and the air pipe that runs through the longitudinals no longer existed or had so many holes and air leaks as to become ineffective.
Now I’ll grant you the heat in a water pumper is MUCH better and easier to manage. LOL!
Operating heat in air cooled vehicles is a skill that few American’s seemed to be able to comprehend. Having to operate several levers and sometimes two separate fans to get the hot air up to the cabin.
The simple fact is most Merican’s had no idea what they were supposed to do to get heat because . . . Well, honestly Merican’s can’t read . . . Or at least refuse to read an owners manual. As they say, some things never change. Most folks still refuse to read an owners manual even for modern automobiles.
At 10 below zero F, you ain’t gonna heat the inside of a Beetle with the air-cooled engine. Cold is the absence of heat, you are in outer space here on earth.
An after market gasoline heater fed from the gas tank would provide enough heat to make the interior of the Beetle comfortable.
Ask me how I know.
Totally agree the Beetle is challenged at -10F.
The VW type 4 engine does a much better job at those temperatures.
A Porsche 911 does even better.
At those temperatures heat becomes a function of displacement and load. Shift to the highest gear and keep your foot in it = more heat.
The problem is that those temps come with icy, snowy roads which makes it difficult to maintain high loads on the engine.
Been there done that . . . But again let’s not pretend there is no heat.
Drove a VW Bug for a few years when I was in college in the 60’s, was a fun car but I needed an ice scraper for the inside of the windshield during winter 😆. Only got some heat if the car was moving at a decent speed, tough to do in heavy traffic.
True, Drump!
I’ve owned several old VWs, so I know. The accessory gas heater helped. So did a warm parka!
Sissies – LOL
In all honesty it has been decades since we be HAD to drive aircooled in anything like -10F.
However, I have done it.
What gets lost in this discussion is that back in that era (late 60s – 70s) even water pumper HVACs sucked. I had a Mazda 808 that struggled to clear glass at -10F.
Also let’s not forget in that era of carbureted cars, getting them started and keeping them running at -10F was no small task. Light bulbs underwood to keep a carb warm was a thing. Then once it was started, carb icing was a real problem eve with heat tubes coming up off the exhaust manifold.
Life was a lot tougher and so were we.
I’m laughing out loud – wish ya’ all could hear me.
I have a 2009 Jeep Wranger that struggles to keep the windshield clear when it snows. The dash vents don’t get air to the sides, corners, or bottom of the windshield. The snow melts up high, and then refreezes at the bottom. If ignored long enough, it will freeze the wipers to the bottom of the glass.
To reiterate, not saying a Beetle is great in extreme cold but here’s a modern example that still has significant problems clearing the windshield.
ROTFL
Only had to do this once, back when I couldn’t afford to pay for such a service. Took a day. Probably lost half the screws to the dash and broke a couple pieces, but got her done.
Another example of design for assembly. When the dashboard is put together at the factory, the tech has access to the whole thing hanging on a hook. Parts are placed from all sides and angles. There are probably gimbals on the line that make it easy to manipulate. Then the entire unit is slid into a passenger door, bolted down and plumbed. Easy-peasy for the assembly line, but now that “wear item” is now buried between the dash and the firewall.
I’ll bet on more than one occasion someone engineered a hatch on the firewall or a drop-out in the dash for easy access. But it went nowhere because the assumption is most people will trade it in long before the core starts leaking, so why bother?
Much like modern gas pump assemblies in the tank. You can drop the tank, or cut a hole in the floor (or bed of the pickup). Because access costs money. And people complain that Apple is satan himself for not having user-replaceable batteries. If Ford could save $10 by welding the hood shut they’d do it in a minute.
“ Another example of design for assembly. ”.
Or . . . You can pursue the opposite approach which is design for Serviceability.
This results in overly complicated, expensive, clunky, and unreliable designs. But, hey, at least they are easy to repair easily which is good because you’ll be repairing stuff frequently.
I’ll gladly take a vehicle that was designed for reliability over ease of repair.
1977 on Impalas had the heater core under the hood making replacement easier.
I suppose so. But then a heater core is just plumbing. My home heating system is designed for easy service and simple boiler replacement, just a few unions. Shutoff valves all around. I guess if I had a pipe break in the circuit it might be a problem to replace it but I wouldn’t have to tear out the floorboards either.
Apples to oranges comparing the heating system in a house with thousands of cubic feet of space vs automotive where we are tying to fit into cubic inches of space. In home heating, weight of the components is barely a concern.
Union fittings in home plumbing not subject to continuous vibration from road inputs. They are clunky to boot and wouldn’t be of any use where you don’t have room to swing a wrench.
Quick disconnect plumbing fittings in automotive are expensive and unreliable in the long term. They have a place in racing but even then they aren’t used much due to their weight.
As others have stated there is a long history of heater cores that n automotive that are more or less easily accessible. They are mostly in older vintage vehicles where space wasn’t at a premium (ie in land yachts) and where weight and fuel economy was hardly a concern (pre-70s).
RK – not trying to attack you personally.
Just frustrates me to no end when folks imply that modern automotive could be so much simpler or easy to service. This is almost certainly said without understanding all the constraints that are imposed (cost, weight, safety, fuel economy, reliability, warranty, harsh operating conditions, etc).
The reality is that heater cores usually last decades upon decades before they fail. It makes little sense to compromise the design of lots of other ancillary components to plan for failure of such a reliable component.
Hi Burn!
I’ve found the old (compact-sized) Frontiers with the four cylinder engine to be very repairable – and reliable. This heater core bidness is the second original part that has failed so far. The other was the water pump. Still has the original starter, alternator, fuel pump and injectors. Clutch, too!
Sorry to hear you are heatless and dealing with a damp and bad smell. A friend and I drove to Truckee one winter in her unheated Jeep. It was 12 degrees. We wore down jackets and hats with more jackets piled all around. No heat is no joke!
I don’t have fond memories of the one time I did that on my first mode of transportation; a ’72 Chevy 1/2 ton. I was 17. Replacing a heater core builds character I guess one could say. Not a fun experience… but it didn’t have A/C, and actually didn’t do much for my character. I wouldn’t wish that experience on anyone Eric. Stay in your happy place.
Yep. In my youth I had to pull the dashboard out of a 1981 Fairmont in five degree weather to do a heater core.
That sucked.
“It is often a job that is beyond the skill – and the will – of the the vehicle’s owner.”
That would be me. I rose to my level of incompetence and had to pay an actual mechanic to replace the heater core on a Pontiac Grand Am I had while in grad school. Columbus, Ohio winters were a bit more than this ol’ Southern country boy was used to.
Done a few of them… ’74 Ranchero was a dash disassembly and quite the chore… the ’87 F-150 was easy-peasy…drop the glove box and open the panel… changed it in Harper’s Ferry at the parts store when we still had to drive to West Virginia for the hunting license.
Merry Christmas all!
‘I’m re-experiencing the days when I drove an old Beetle that didn’t have a heater core.’ — eric
Spare a thought, as you listen to the jingle of sleigh bells in the snow, for EeeVee victims driving in freezing cabins with heavy parkas to ‘conserve range.’
It didn’t have to be this way …
I just did this on my 89 Dodge D100… The biggest problem was crumbling 35 year old plastic.
On the other hand I also removed 35 years of leaves and twigs…
BTW what is this “AC” you speak of? Is ths another name for the window vents? 🙂
Good stuff, Warren!
And- yeah – I am expecting to find (and clear out) 23 years’ worth of twigs and such, too.
Have fun with that, Eric. It’s amazing how much crap is jammed behind the dash board of modern vehicles. Working on it will make you sass your preacher.
I just replaced a starter relay on my ’06 Corolla. After removing the driver seat I was able to contort myself to get to it. It was placed behind a small support bracket that you can only get to by going after it from the firewall side. I had to depress the brake pedal with my head to get access to it.
Ahhh…good times…
I will keep you and everyone here posted, Mark!
Hoping to swing by my buddy’s shop today to evacuate the AC so I can disconnect the lines. Then over the weekend, I’ll try to find the time (and gumption) to dig into the dash and get that old leaking core out of there!
You might want to pick up a Little Buddy propane heater for just such an emergency. At least you’d have heat in the cab. Also useful when camping or working in an unheated shop.