ENGINE COOLING | How It Works


– Alright, alright,
alright, alright, now Bart. Yeah? What’s cooler than being cool? Ice Bart. Oh yeah. (electronic music) Hey there cool kids, today we’re talking about
something I know a lot about, being cool.
(children cheering) If you’re watching this, you probably already know how to be cool, but what about engines, huh? How can an engine be cool? Please tell me how to be cool Shut up, nerd engine,
you’ll never be cool, you wear glasses. Now get out of here. Ugh, I’m sorry you had to see that folks. An internal combustion engine
is a lot like my inner thighs, it produces a lot of heat. You gotta keep engines from overheating and sometimes you gotta
keep them from freezing. Some people live in places
where it freezes, weird. In that case, you’d need something to
do the opposite of freeze, some sort of antifreeze. (man maniacally laughing) Antifreeze is also referred to as coolant when it’s mixed with water if you’re like me, you may
have thought that coolant referred to an ant that
has a bunch of tattoos. Well, it doesn’t. Coolant is a liquid that prevents your
engine from overheating. Wait a minute, the same liquid can keep
your engine from overheating and keep your engine from freezing and make you go blind if you drink it? That sounds unpossible, but true. You could just use water
to cool your engine and it’d do a decent job but there are more than a few problems with relying on water. One, in extreme heat it boils over, it overheats and damages
the engine and two, in extreme cold, it freezes, expanding and breaking the engine. Antifreeze is a chemical mostly consisting of ethylene glycol or sometimes the lower
toxicity propylene glycol. When mixed with water it serves
to lower the freezing point and raise the boiling
point in the mixture. It also includes some corrosion inhibitors that are needed to
prevent rust from forming on the metal parts like water
pumps and engine blocks. When the antifreeze gets
brow or rusty in color that means the inhibitors are broken down and the antifreeze, now just like a pet dolphin that ran away, needs to be replaced. Antifreeze works because the freezing and boiling points of liquid are colligative properties, meaning they depend on the
concentrations of solutes or dissolved substances in the solution. A pure solution freezes
because the lower temperatures cause the molecules to slow down allowing the natural
attractive forces between them to capture and bind them into
rigid crystalline structures, but adding a different
kind of molecule to the mix blocks those attractive forces and prevents the crystalline
structures from forming. The more solutes that are added, the lower the temperature needs to be before the solution can properly freeze. If you’re confused, don’t worry, so am I, all the time, about everything. Why am I being filmed? See when water freezes, it crystallizes and expands like your mom. When water had something dissolved in it, the molecules have to work more to get near each other to crystallize. That extra work to crystallize
drops the freezing point. That’s why road salt works,
it dissolves in water or on contact with snow or ice, and if it dissolves, it
breaks up the crystals and makes the crystals harder to form, but salt, even when dissolved in water, can still be hard enough
that when they shoot around in a closed system like your
engine, they could do damage. Ethylene glycol works great ’cause not only is it water soluble, it’s what we call miscible, which means it can be
mixed with any amount and still mix evenly. Antifreeze and water should
have a mixture percentage based on the lowest temperatures typically seen in your climate. In most regions, these are
50-50 water-antifreeze mixture which will provide sufficient protection from little below freezing
to a high of 265 degrees. In the coldest temperatures, you could use a mix of
60 to 70% antifreeze. The color of antifreeze
is from a coloring dye. Not just the chemical
used but specific colors often mean something differently
in the chemical makeup. The main antifreeze
colors that you run across are the tradition green
and extended-life yellow and extended-life pink or orange. Antifreeze has got a specific color and that’s so if it’s
leaking, you know what it is. Now to see how that
antifreeze gets around, let’s go inside the engine. – You wanna go inside of me?
– What? No, shut up nerd engine
and get out of here before I blow you up. Sorry gang, I gotta
take care of that engine like I took care of Mr. Carburetor when I found out he stole my kidney. You think I wouldn’t find out, huh? – Calm down, Bart, we can talk about this. (thudding)
(metal clanking) Oh, what are you, please, times are tough. Please, oh. (thudding) I’m sorry. (Carburetor crying) I’m sorry. – Coolant flows through a path that takes it from the water pump through the passages
inside the engine block where it collects more heat
produced by the cylinders. It then flows up to the cylinder head, or heads in a V type engine, where it collects more heat
from the combustion chambers, then it flows out past the thermostat, if the thermostat’s
opened up to let it pass, through the upper radiator
hose and into the radiator. Here the coolant flows through
the thin flattened hoses that make up the core of the radiator and it’s cooled by the air
flow across those vents. The coolant flows out of the radiator, through the hose and
back to the water pump, by this time cooled off and ready to go grab more
heat from the engine. A car’s water pump’s used to
send fluid to the engine block. It’s a simple centrifugal
pump driven by a belt connected to the crankshaft of the engine, and that uses centrifugal force to send the fluid outside while it spins, making it drawn in from
the center continuously. The inlet of the pump is
located near the center so the fluid returning from the radiator hits these pump veins. Pump veins fling the fluid
to the outside of the pump where it can enter the engine in there, makes it way through all those passages in the engine and the cylinders where it returns to the
cylinder head of the engine. Thermostat’s located where
the fluid leaves the engine. The plumbing around the thermostat sends the fluid back to the pump directly if the thermostat’s closed. If it’s open, the fluid goes
through the radiator first and then back to the pump, thermostat’s regulating
the amount of water that goes through the radiator. Nowadays a lot of these mechanisms are controlled by computers but the secret to the
thermostat used to lie in a small cylinder located in the engine side of the device. The cylinder is filled with a wax that begins to melt at around
180 degrees Fahrenheit. A rod connected to the
valve presses into the wax and when it melts, it expands a bunch, pushing the rod out of the
cylinder and opening the valve. That’s how turkey thermostats work. Bing. Life hack, if you wanna reuse them, put a rubber band around them and let it cool off in your fridge and then you stick it in
whatever turkeys you want. How many turkeys are you cooking? None, one a year, and you
probably did it wrong. The radiator essentially takes
the heat from the coolant and gives it to the air. Most modern cars use aluminum radiators. They’re made by brazing thin aluminum fins to flattened aluminum tubes. The coolant flows from
the inlet to the outlet through all of these tubes
mounted in parallel arrangement. Fins conduct the heat, transfer it to the air
flowing through the radiator. Sometimes these tubes got a fin
inserted called a turbulator which is what I’m gonna name my first kid. The turbulator increases
the turbulence of the fluid flowing through the tubes. If the fluid flowed evenly, only the stuff actually touching the tube would be cooled directly. When you create that turbulence, more fluid is getting cooled. (children cheering)
Crazy, you guys are so smart. This means more heat’s extracted and all the fluid inside the
tube is used effectively. All this talk of fluid in tubes reminds me of the lab
where I was conceived. Now, the radiator cap itself actually increases the
boiling point of your coolant by about 45 degrees. Works the same way a pressure cooker prevents water from boiling. The cap is actually a
pressure release valve and on cars it’s usually
set to about 15 PSI. The boiling point of water increases when the water is placed under pressure. It’s got no where to
expand and turn into gas. Water below sea level
boils at higher temperature ’cause it’s under more
pressure from the atmosphere. When the fluid in the
cooling system heats up, it expands, so the pressure builds. The cap is the only place
where this pressure can escape so the setting of the
spring on the cap determines the maximum pressure
in the cooling system. When the pressure reaches that point, it pushes the valve open, allowing coolant to escape
from the cooling system and keeping the pressure
where it should be. The coolant flows
through the overflow tube into the bottom of the overflow tank. This arrangement keeps
air out of the system, and when the radiator cools back down, it creates a vacuum in the cooling system, pulls open another spring
in the loaded valve, and that sucks water back in from the bottom of the overflow tank to replace the water that was expelled. Used to be you just had a big
old fan driven by the engine cooling all of this off, but nowadays the cooling
fan is controlled externally to maintain a constant engine temperature. Some fans are controlled either
with a thermostatic switch by the engine computer and they turn on when the
temperatures of the coolant gets above a set point, and turn back off when the
temperature drops below. There’s also a separate
circuit for the heating system. This circuit takes fluid
from the cylinder head and passes it through a heater
core, then back to the pump. Heater core, located in
the dashboard of your car, is really a little tiny radiator. The heater fan blows the
air through the heater core into the passenger compartment of your car and keeps you warm. The heater core draws it’s
coolant from the cylinder head and returns it to the pump,
so it works regardless if the thermostat’s open or closed. If your car is overheating,
you can turn on the heater and it can pull hot air
from the engine compartment and cool off your engine. I’m sorry everybody, I
can’t do this anymore, I got a confession to make. It’s something I’ve been hiding for at least several minutes. Well, here it goes.
(dolphin chirps) Liquid is not the only
way to cool an engine and I created a human
dolphin hybrid in the lab. Oh, it feels so good to get off my chest. So yeah, there’s liquid cooled engines and air cooled engines. Technically, all engines are air cooled because even water cooled engines
use air to cool the water. Mind-blowing right. Well, pick your jaws up off
the floor and I’m gonna go on. Air cooled engines have fins extending out that pull heat away. Cool air is forced over the
fins typically by a fan. Those air cooled Porsches and
VW engines were boxer engines because they can expose
more surface area to the air to cool ’em off. The explosions in the chamber aren’t serving to warm up
a huge solid engine block, just their own chambers. Also, they’ve got what
amounts to essentially a fan in the engine to pull air through, and those crazy, distinctive
holes in the back and all around those old
Porsches and Bugs and vans, well they’re there to let
as much air as possible in so that it can get around
and through the engines. So, if there’s enough air
flow, those dang ol’ engines, they’re gonna last just about forever. These days air cooled engines
mostly show up in motorcycles, all-terrain vehicles, riding
lawn mowers and aircraft. Personally I got an air cooled engine in my all-terrain riding
law mower helicopter cycle. Join us n… Who are you? – It’s me, Bart, nerd engine. Turns out I was just overheating. I put some coolant up inside me and boom, my glasses fell off and now I’m cool. – Boy, I’ll say you are. You’re the coolest engine I’ve ever seen. Say nerd engine. – Yes, Bart. – Do you maybe wanna go to prom with me? – I thought you’d never ask. – Woo-hoo-hoo! Cooling an engine! Click the yellow button
to subscribe to Donut, we got new shows coming out every day, you don’t wanna miss a thing. Oh, check Nolan’s WheelHouse
on air cooled Porsches. Check out this episode of Hot Lap. Follow us on Twitter and
Instagram @donutmedia. Follow me @bidsbarto. Got to shop.donut.media, we come up with a new piece of
merchandise every dang week. Don’t tell my wife I’m
taking nerd engine to prom.

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