This is the advice given today in the NY post by Robert Sinclair Jr, spokeman for the Automobile Club of New York. Does this work? And if it does, why?
In older cars the heater drew heat away from the engine. I don’t believe it is as true with newer cars.
It’s still true with modern cars. In theory, turning your heater on high should slightly cool your engine.
The way your heater works is, it taps into the car’s cooling system. And takes heat from the engine coolant
and uses it to warm up air, which then gets blown into the cabin.
The coolant then flows back to the radiator and loses even more heat. Then it is pumped back through the engine and picks up heat. Then it the goes back to the radiator, where some of the heat is radiated away. Then back into the engine to pick up more heat, etc, etc.
There’s a smaller radiator in the car’s cabin heating system that air that’s supposed to be hot flows over. The air picks up some of the heat from the coolant, and gets blown into the cabin as warm air.
In theory, every time a little heat gets taken out of the coolant, it can absorb more heat the next time through the engine. So paradoxically, turning your heat up blasting high can draw more heat out of the engine.
At least that’s the theory. I’m really not sure if it works in practice. The effect may be too small to make any difference. Really, if your car is overheating so bad that you notice it, there’s probably something wrong. And you should pull over and invoke your AAA membership (which you DO have, don’t you?) for a free tow to the mechanic’s.
-Ben
The why of the matter is because the radiator and the heater use the same source of heat: the engine’s cooling water.
The radiator is a big heat exchanger, allowing the heat of the coolant to conduct itself to the outside air, which is usualyl moving past the radiator due to the car’s motion. The heater core is a similar device, but smaller, that allows the coolant to exchange heat with the cabin air, usually by warming external air that is blown into the cabin. TV time’s claim implies that heater cores no longer work this way, but I never heard that.
Cars used to overheat generally because the engine was working too hard while the car wasn’t moving, or the outside air temperature was too high, or both. New cars produce less waste heat and have better cooling system designs and include electric fans to circulate extra air past the radiator if the coolant temperature gets too high.
My 1991 Ford Escort has a poorly designed cooling system. The car overheats quickly in the summer, and won’t heat up at all if I drive at highway speeds at freezing temperatures. It just sucks. But I have noticed that when it does overheat in the summer, the heater trick works. And when the car stays cool during winter highway trips, I don’t have ANY heat at all. I made one trip to Denver via I-40/I-25 a few Decembers ago, and I wound up wearing three layers of pants and five layers of shirts… but I didn’t have any extra socks. It was miserable, my feet froze from about Flagstaff all the way to Denver!
Whether or not the effect is noticeable depends a lot on the relative size of the engine, the ambient temperature outside the car, and the way you continue to drive the car after it has shown signs of overheating.
Tests I did on a Honda Civic with a thermocouple probe showed that the engine coolant temperature was reduced nearly 12 F by turning the heater on full blast in the middle of Summer, while doing easy driving around town.
Also note that just turning off your air conditioner will allow the car to run cooler, as then it no longer has all that heat dumped from the condenser in front of your radiator, and the engine works slightly less hard.
No, I don’t have a AAA membership. I’m a native New Yorker, I don’t even know how to drive.
Still, pulling over makes much more sense than turning on your heater, especially when it’s 100 degrees.
How well it works depends upon a lot of factors, like what kind of shape your heater core (the thingie in the car which the outside air flows through to get warmed up), how much air your heater fan can push through, and why your car is overheating.
If there’s no coolant in your car, it ain’t gonna help at all. Otherwise, it will drop your engine tempature down several degrees. It might be enough to keep from blowing your engine, it might not.
In any case, if you’re unlucky enough to own a car with idiot lights that simply come on when the engine over heats, your best bet is to set the heater on full blast and pull off the road as soon as possible (don’t set the air flow to recirculate, you want fresh, cooler air to run through the core). If your car’s got a temp gauge you can watch it and if the needle starts dropping, and stays low, you’ll be okay to continue driving.
I used this to keep my Honda running for months when I needed to do some work on the radiator, but didn’t have the money for the parts.
While the heater as annex to your engine’s cooling system aspect of this question has been addressed, the real life saver aspect has not.
As mentioned above, when all is well, your car’s heater operates off an adjunct to the cooling plumbing, a bypass in the plumbing that is open when your heater’s on and closed when it’s off. When your engine’s cooling system is hunky-dory, everything’s pretty much full of coolant, so when you’ve been running the heater and shut it off, X amount of coolant that is in the bypass at the time you shut the heater off goes out of circulation.
Now were talkin’ summertime and you haven’t run the heater in months. And we’re not talking about a car that tends to run a little hot - we’re talking about you driving a car on the freeway that’s actually experienced a split radiator hose and the temp guage’s movement towards Valhalla is visually perceptible.
So you open that heater portion of the cooling system (by turning the heater on) and you dump the relatively cool (uncirculated for months) contents of the heater reservoir into the engine’s deprived cooling system and gain another 1000 yards of operation to get yourself out of traffic and off the road before the crankshaft becomes one with its bearings.
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I’ve been driving my brother’s '83(?) Buick Skylark all summer (no AC at all) and my dad warned me to turn on the defroster full blast or the car would overheat. Every single frigging time I get out of the car people ask me if I’m O.K. because my face is beet red and I’m pouring sweat. It truly sucks, but it works.
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Do you guys think the heater would work better? And do I really have to have the temp on as hot as it will go? This isn’t something I want to experiment with since I don’t have AAA either, and if the car breaks down the first thing my dad will ask me is if I was running the defroster.
Shannybonny I used to drive a series of Novas and Buicks with huge engines. And drove 'em til they dropped.
The defroster works the best, only because it tends to keep the heat up rather than expelling it onto your feet/lower body. One assumes your windows are cranked wide open, so the heat goes out faster. And yes, it works.
My big ole blocks would overheat while sitting in traffic on a 90 degree day, and the idiot light would come on. I could turn on the defrost, heat set to full hot, fan on high, and within 15-20 seconds, light went out.
I have to do that every day. My electric fan stopped working. It’s obvious the difference it makes- Turn off the heater for a few miles, then on again, and the air stream from the heater will nearly scald you.
Yes turning on the heater to keep the engine cool does work as the above posters stated, but you must go at a reasonable speed for it to work. Such as you notice car is overheating, you are in middle of nowhere, you turn on the heater, but you only drive 5MPH. This will NOT cool your engine. You must drive fast enough for air to be drawn into the engine compartment.
I’ve taken a shop class (22 years ago) and this method was mentioned. I’ved used it with success. However, it is no substitute for pulling over and checking the coolant level, or just turning off the engine when it overheats until it cools down. A cracked block from overheating is very expensive, and entirely avoidable.
TV Time’s answer that this trick sometimes doesn’t work with some modern cars is correct. I have seen a few that draw the heat for the internal heater from a shroud around the exhaust manifold, rather than a radiator off the main cooling system. I think because the latter system tends to gum up and stop working in cars used in hot climates (like where I live) where the heater is used very little.
I would guess that based on my experience, less than 1% of the cars on the road use this system. I’m pretty sure the VolksaPorsche 914 did, as well as the Beetle and Kharman Ghia…and the Fiat 850 I think. Can you give some examples of modern cars that do not use hot coolant as a heater working medium?
As for gumming up…I really am not certain about that, but I suppose if you had a car that never ran the heater for years at a time, you might see that…
Bear in mind Anthracite that I’m in Australia, and I probably see a lot more Japanese and Australian built cars than you do. And even the cars that are nominally the same often have a different spec over here. But to answer your question, my parents had a Subaru that used this, then I’ve seen it on a couple of Nissans. But as you say, it’s certainly not the most common system.
And as to problem of the more standard heating system filling up with rust and radiator mud, believe me having restored a couple of old cars that had lived in Brisbane (where the average wintertime temp is 25 degrees Celcius) they do get clogged up and cease to work as a result.
I had a 1984 Toyota Tercel and I can guarantee that using the heater significantly reduced the temperature in my under-cooled car.
This summer me and some friends went on a road trip from Orlando to Key West, five of us on a honda civic for 7 hours. On the return trip the radiator cracked between the Keys and Miami, we had about 12 dollars between the 5 of us (damn strip clubs) so we really had no options at that point. A cop happened to pull up and told us we could try running it with the heater on full blast. Well it worked, 6 and a half hours of five people in a honda civic going with the heater on in the middle of summer in Florida. Next year we are taking a plane, no amount of washing has been able to take the funk out of that car.
Yup. I have had several cars with a tendency to overheat where I was forced to use the heater in summer. I guess it is not as obvious to others as it is to me but the hater in the car cabin is just a smaller version of the radiator in front. if you have 8more* radiator at work, you have more cooling. It is really quite simple. BTW, the internal heater bypasses the thermostat, unlike the external radiator.
For what it’s worth, I took a trip from Colorado to L.A. a while back, and traveled during the day on the return trip back home. I had been running a 96 Neon Sport for about three and a half years at that point and had never seen the temperature gauge go above “the middle” (a most techincal term for whatever temperature the engine gets when it is operating normally and all warmed up).
That trip through eastern California in the early afternoon was INCREDIBLY hot, and the needle was getting near the danger zone when I turned the heat on full blast. The temp dropped almost immediately (and I almost did along with it – I’d schedule in some night driving if I ever had to do it again).
the Holy Avenger