While I never identified myself as a "hillbilly", per se, I did grow up in a rural area, and, well, I guess I sort of am one. Which is totally fine, really.
But, unlike most "hillbillies", I don't know crap about cars. At lest, not by comparison. I am, however, pretty familiar with how things on cars work that I have had to replace, the cooling system being one of them. So this post is sort of a PSA for car newbies, by a car newbie.
The reason for my post is because whenever I've advised some one with an overheating car to blast their heat as high as it will go, they always react with shock. "What? That's stupid! The problem is that there's too much heat! I'm trying to get rid of heat! Why would I want to make more?"
Trust me, I've been dealing with over-heating cars since I started driving. Don't believe me? Google it!
The surprise that people have is a result of their lack of knowledge of how their car's heat works. It's not a furnace or heater like some people think. The heat is actually a waste product that come from the car's engine.
What's going on here?
Here's a pretty basic overview of a cars cooling system, and it is in no way comprehensive. (I'm sure there is some small number of cars that have other types of cooling.)
Tubes run through and around the engine. These tubes are filled with anti-freeze, engine-coolant, and water. It's usually green, so I like to call it by its technical name "green car juice". (It's not juice, though. If you drink it, you'll die.)
The heat from the engine is absorbed though the tubes into the green juice. The juice is then pumped through something called a radiator.
At it's most basic, all that a radiator is made of is a series of tubes (like the Alaskan internet) with lots of bends. There's all these bends so that you can squeeze more pipe into a little square area. Wind blows over these pipes, and the heat is carried away in the wind, thus cooling the engine. In cars, there's little pieces of metal, called vanes, that cover the pipes in the radiator. These help dump hear out into the air because they conduct heat away from the pipes, and in that way increase the exposed surface area of these pipes.
When there's no wind, the radiator gets pretty hot. There's a pretty big electric fan that sets in front of the radiator that turns on so the car can make its own wind. This usually happens when the car is idle and not moving. The current that's needed to turn the fan is loaded into the car's electrical system, which runs off of mechanical energy from the car's engine. When the load increases, the car has to run faster. This generates more heat. You can see that this is not very efficient, and know you know why your car can overheat even when standing still.
So why do I turn on the heat when my car overheats? Well, those green juice filled tubes are connected to a little set of tubes that go into the part where people sit. (I don't know what that part is technically called. Interior? Cockpit? Flight-deck? Crew-Cabin? I'll just call it the cockpit, since that sounds like a bad-ass fighter jet) And connected to those little tubes is a miniature radiator called a heater core.
When you turn the heat on, valves open that allow the hot green juice to flow into this heater core. When you "blast" the heat, you're opening the valves as far as they go, taking the most amount of heat from the engine and into the cockpit as your climate control will allow. And if you look at your climate control controls (wait... yeah), you'll see that little "Fan" knob that turns on a little fan to blow hot (or cold) air into your face faster. Sounds a lot like the big radiator I described earlier, doesn't it?
So, if your car is overheating, and you open the windows and blast the heat, you should see a drop in engine temperature. This is by no means a solution to your over-heating car problem, and is only an emergency fix to allow you to get somewhere safe or to a shop or wherever you can fix the problem. BUT DON'T OPEN THE RADIATOR OR COOLANT RESERVOIR UNTIL THE ENGINE IS COLD!
Death by radiator
My entire childhood, all the men in my life who were giving me car advice always said "Always open the radiator slowly." but they didn't explain exactly why, or specifically what they meant by slowly. I knew it was to avoid injury, but that's about it. I thought I could just put a rag over the cap and turn it slowly and it would be fine. WRONG.
When the car is running, and the engine is "at temperature", fluid in the cooling system can reach temperatures above the boiling point of water. "But wait," you say. "Water boils at 212°F and turns to steam or water vapor or something. Water doesn't go above 212°F!" Well, if you're talking about boiling a pot of water on the stove, you're correct. But, in a car's cooling system, things are a little different. Because the cooling system is (supposed to be) a closed system, the water that goes beyond boiling point is forced to stay liquid because of the pressure it's under. You can think of it as the steam having no where to go. (This might not be exactly scientifically correct, but is a close analogue to what's going on here.)
When you open the cooling system by turning, even slightly, the cap on the radiator and/or coolant reservoir, the pressure that fluid is under becomes significantly lower, the steam has somewhere to go, and forces it's way out of the hole you just opened. And remember, the steam and/or water vapor doens't have a limit of 212°F, so it could be much higher. And when that super hot water, steam, vapor, engine-coolant, and/or anti-freeze comes flying out at your hand, arm, torso, and face, it's going to be going very, very fast.
This is how people receive sever burns, get blinded, or die, when opening the radiator on their car.
So what did they mean by "Open the cap slowly?" To understand that, we can look at another instance of opening a vessel that's under pressure: The two-liter. Soda (or 'pop', if you're from Ohio) has bubbles. The Pop company mixes water, sugar, and other ingredients together, and then pumps the bottles or cans up with high-pressure carbon dioxide gas (CO2). The CO2 is pumped in at such high pressure, that it dissolves into the pop.
When your car overheats, the gases that want to escape the cooling system dissolve into those green juices. They're under a lot of pressure in there.
Imagine a pop bottle that has been shook up. We all know that when the bottle is opened, sticky pop is going to go EVERYWHERE. (Less common is the knowledge that pop-bottle caps have blown off explosively and, yes, killed at least one person. I don't remember the details, and find it hard to believe myself) But if you open the cap really, REALLY slowly, and I'm talking like a millimeter at a time, the gas can come out slowly enough that it doesn't splash pop everywhere.
And that's what "Open the radiator slowly." means. Not turning the cap slowly, but moving it an incredibly small amount, and then stopping and waiting, and then doing it again. It's still really dangerous, though, and I just recommend you wait until your car cools off, because if you screw up, that cap is coming off like a rocket, and the hot juices will be right behind.
One day I was desperate and stupid and opened an overheating car's coolant reservoir. The reservoir was made of clear plastic, and since I was doing it slowly, I could see the liquid inside it turn into a bubbling, boiling mass with every turn of the cap. It took about 15 minutes, but I was able to get it open without injury. Still, though, a bad idea. I won't ever do that again to an overheating car, but I will forever open all radiators slowly, in case they're hotter than I thought.
From bad to worse
So what happens when Murphy's Law comes into play? Imagine a half hour road trip across three different interstates that turns into three and a half hours because of bad directions and all three interstates have rush hour traffic and collision induced traffic jams. It's getting dark. The baby is crying. All three adults on board have to pee. And now your car is overheating. (This is a true story). Now, if your fan is electric or mechanical, it takes energy away from the engine. When this happened to me, my battery started to die. Press the gas peddle, and the alternator charged the battery back up. But then the engine got too hot. Windows down, and blast the heat, and let off the gas. Engine cooled off, battery got weaker. Give it more gas. Battery juiced back up, engine got too hot. Off thew gas, engine cooler, battery dead-er. Back and forth. Back and forth. For THREE AND A HALF HOURS!
So I put in more of that magical green juice and PRESTO all better!
Maybe next time I'll explain that toilets don't have drain valves. ;-)
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