Lesson 3:Engine Lubrication & Cooling

What we will cover:In the last lesson we learned about the

incredible temperatures and speeds at which engine parts operate. An engine could not run for very long without some way of reducing the friction between moving parts and controlling the temperature of engine components.

In this lesson we will learn how oil and coolant perform these important tasks for us, and what we can do—as car owners—to ensure that they will continue to do so for a long time.

Part 1: Engine Lubrication

The purposes of engine oil:Pistons, valves, and all of the moving parts in the engine would get very hot and fail quickly if they were actually rubbing against each other inside the engine. Fortunately, they are not. All of the moving parts inside of your engine have a very thin film of oil between them, keeping metal from ever contacting metal.

When the engine is not running, all of the oil

sits in the bottom of the engine in the “oil pan.” Once the car is started, an oil pump begins to

deliver oil to the rest of the engine.

Oil is pumped throughout the engine, so that it is constantly

circulating and lubricating all of the moving components.

Oil Pan

Why does Oil Need to be Changed?Oil’s job is a tough one. Today’s oils contain many additives

that help them to hold up under the extreme conditions they are subjected to. However, even the best oils break down with time. They become contaminated with dirt, moisture, and fuel—all of which are poor lubricants!

For these reasons, old oil needs to be drained and replaced with new oil regularly. Oil that is not changed will start to turn into “sludge,” plugging critical oil passages. Additionally, over time, moisture in the oil causes corrosive acids to form, which will begin to damage internal engine parts if the oil isn’t changed.

When the oil is changed, the oil filter should also be replaced. This filter is usually located on the side of the engine and helps to trap some of the

harmful particles that might be circulating in your oil.

To learn more about changing oil, return to I-learn now and watch the video entitled “Changing Oil.” Even people who have changed their

own oil before will learn some new things from this video.

How do dirt, moisture, and fuel get into my oil?• Dirt comes from dust in the air taken into the engine on the intake stroke, which gets past the piston into the oil• Moisture also comes from the incoming air; it gets into the warm engine and condenses when it cools down• Small amounts of fuel also get past the pistons and end up in the oil

Forget to Change Your Oil?

This picture shows sludge on an engine’s timing chain and camshafts.

This is a result of not changing the oil often enough. When oil becomes thick like this, severe engine damage has probably already occurred.

Forget to change your oil?

This photograph shows a piston that was removed from an engine that was neglected. The owner forgot to change his engine oil for over a year.

The scoring on the side of the piston give us an indication of how much friction and heat are developed when an engine lacks plenty of good, clean oil.Scoring that occurred when this piston

and the cylinder wall were contacting each other without a film of oil

between them.

How often should you change your oil?

Dusty conditions Cold weather Hot weather Short trips (less than 15 minutes) Stop-and-go city driving

People are often confused about how often to change their engine oil. Many owner’s manual maintenance schedules call for oil change intervals that range from every 5,000 miles to every 12,000 miles. Yet, you will hear others say it should be changed every 3,000 miles or every 3 months. Who i s r igh t?

Your owner’s manual can usually be trusted! If your owner’s manual calls for a very long interval between oil changes (such as 10,000 miles or more), make sure to read the fine print. This interval is likely only valid if you are using a specific brand of synthetic oil and under normal or “ideal” driving conditions only. If you drive your car under any of the following conditions, your oil becomes contaminated and breaks down much faster:

What this means for you: nearly everyone drives their car under one or more of these severe conditions. Therefore, you should change your oil frequently, regardless of how many miles you drive. The safest recommendation is to change it every 5,000 miles or every 6 months (whichever comes first)—if you want your engine to last! If your engine does fail, it will cost you $3,000 - $8,000 to repair it; changing your oil is much less expensive!

Checking Your OilChecking your oil is just as important as changing your oil. In the first slide of this lesson we learned that keeping your oil full and keeping it changed are the two most critical things you can do for your engine.

How often should you check your oil level?

You should check your oil level every week. Many people make a habit of doing this each time they buy fuel. But, no matter when you choose to check your oil, the important thing is that you are doing it! The oil level in your engine drops for two reasons:

1-Every engine burns some oil during the combustion process2-Many engines leak some oil past the seals

Since an engine can suddenly—and without warning—begin to burn or leak more oil, watch for signs of these problems such as smoke coming from the exhaust pipe or drops of oil on the ground. Check your oil level immediately if you see this. But remember that even brand new engines consume some oil and may run low if not checked regularly.

How to Check Your OilTo check your oil, follow these steps:

1. Make sure the engine has been off for at least 2-3 minutes2. Open the hood and locate the engine oil dipstick (refer to your

owner’s manual to make sure you are using the correct dipstick)3. Pull the dipstick out and wipe if off with a rag4. Reinsert the dipstick, making sure it is fully seated5. Remove the dipstick again and look for the oil level on the dipstick.

What are the marks on the dipstick for?

On the dipstick you will likely see a “full” mark and an “add” or “low” mark. The oil should be to the “full” mark. It takes exactly one quart of oil to raise it from the “add” mark to the “full” mark.

The color of the oil is also an indicator of its condition. The picture on the left shows used oil (at the “add” mark) just before it was changed. The oil on the dipstick to the right is new—just after an oil change.

“Full” mark

“Add” mark

Adding OilIf you need to add oil, determine the correct type of oil, locate & remove the engine oil fill cap, and pour it in (you may need a funnel). Be careful not to over-fill it. If the oil level gets too high in the oil pan, the crankshaft and pistons can begin to splash in the oil, causing it to become foamy and aerated. Over-filling an engine with oil can damage your engine just as easily as letting it get too low can.

Engine oil dipstick

Engine oil fill cap

What type of oil should you use?There are two important considerations to make when choosing the oil you will use in your car:

1. It should be the correct viscosity and type for your car2. The oil should be API certified

(We will discuss what both of these mean in the next two slides)

There are some other factors that do not matter and are personal preferences only:

• The brand of the oil• Whether it is synthetic or conventional oil (some cars call for a specific type of

synthetic oil. Very high quality synthetic oils do last longer and provide better protection, but as long as you change it often, conventional oil will suffice)

What is Oil Viscosity?Viscosity is a measurement of how easily oil flows at a given temperature. Oil acts a lot like maple syrup—if it is warm, it is thin and flows easily, but if it has been in the refrigerator, it is thick and flows slowly.

Oil is assigned a weight based on its viscosity. The lower the number, the thinner the oil will be. For example, a 40 weight oil is a lot thinner than a 75 weight oil, but a 10 weight oil is even thinner than them both and will flow more easily in cold temperatures.

Today’s engine oils are “multi-viscosity” oils—for example 5W-30 or 10W-40. If an oil has a viscosity, or weight, of 5W-30, it is formulated to act as a 5 weight oil in the winter and a 30 weight oil in the summer. Because of this, the oil will be thin enough to flow in the winter, but thick enough to provide lubrication in the summer. Therefore, the same oil can usually be used all year long.

It is important to use oil with the right viscosity

for your engine!

While you may hear a lot of different things and people may try to sell you many different kinds of oil, the safest advice is this: Always use the type and weight of oil called for in your owner’s manual.

What is “API Certified”? The American Petroleum Institute (API) sets standards for motor oil. If a motor oil meets these minimum standards, one or both of the seals shown below will appear on the bottle. If it doesn’t have these seals—don’t buy it!

Don’t Dump Your Used Oil!Used motor oil should be taken to a facility that will recycle it. If it is dumped on the ground or down a drain it can have detrimental effects on the environment.

Did you know? One gallon of used motor oil (about the amount obtained from one oil change) can contaminate up to 1 million gallons of drinking water!

Most auto parts stores will take your used oil for free. If you choose to change your own oil, just put the used oil in a container (like an empty milk carton) and drop it off to them. These facilities will make sure your oil is recycled or disposed of properly.

Keep an eye on your instruments!

Most cars have an oil pressure light on the dash. A few cars have an oil pressure gauge instead. Either way, your dash instruments should alert you if the your engine’s oil pressure gets too low.

Your car has a sensor on the engine that constantly monitors your oil pressure. It is making sure that the oil pump is pumping the oil with enough pressure to reach all of the parts of your engine.

Your oil pressure light should be on whenever the engine is not running, but should turn off within a few seconds of starting the car. If the light remains on or comes back on while the engine is running, pull over and shut the engine off! Check your oil level first. If it is fine, get your car to a repair shop

and have it checked out. By turning the engine off quickly, you may just save your engine!

Warming your engine on cold days

Start your engine & wait until the oil light on your dash turns off Drive away slowly—don’t rev the engine or accelerate quickly Avoid idling the engine for long periods (letting the engine idle while the heater

warms up is not recommended) Never drive your car until your windows are completely clear of ice and snow! If you have a garage, keep your car parked there; garages stay warmer

When it is very cold outside, your oil is also cold.

Most of your engine wear happens right after startup on these cold days because the oil cannot reach or lubricate all of the moving parts very quickly.

Here are some tips to minimize engine wear and help your car to last longer:

When your car is idling, the oil pressure is low. When the oil is cold, it is thick and doesn't lubricate the engine very well. Combine both of those factors--idling when the oil is cold--and it's twice as hard on your engine.

Part 2: Engine Cooling Systems

The Purposes of the Cooling System

The cooling system does exactly what you would expect—it helps to control the temperature of the engine. It performs these two basic functions:

1. The cooling system keeps the engine from getting too hot—the engine would be permanently damaged if it overheated by even a few degrees.

2. The cooling system helps the engine to warm up quickly once it is started. This is important because the engine doesn’t run efficiently until it is warmed up.

How the Cooling System Works

Coolant (also called antifreeze) circulates around the outside of the engine’s cylinders in “water jackets.”

The coolant absorbs heat from the combustion process and carries it away to the radiator. The radiator is usually near the front of the car where air passes through it and cools off the hot coolant.

Once the coolant is cooled off, it returns to the engine to absorb more heat. This process continues as long as the engine is running.

Water Jacket

Cylinder

Remember—the cylinders are where the pistons travel up and down and where the combustion takes place.

How the Cooling System WorksWhen you first start your car, the water pump begins turning and circulates the coolant around in the water jackets. However, until the engine and coolant get warmed up, a thermostat stays closed and blocks the coolant from flowing to the radiator. This keeps the warming coolant in the engine and helps the engine to warm up quickly.

As soon as the coolant is warm enough, the thermostat opens and the hot coolant begins to flow to the radiator.

When the car is moving down the road, air flows through the radiator, cooling this hot coolant. But, if the car is not moving (or is driving slowly), a fan turns on and pulls additional air through the radiator, preventing the coolant from getting too hot.

Cylinders

Pressure Cap

Thermostat Regulates flow of coolant

Water Pump Circulates coolant

Fan pulls air through radiator

Water Jacket

The pressure cap (also called a radiator cap) seals the system, allowing pressure to build as the coolant heats up and expands.

Go back to I-learn now and watch the video entitled “How the Cooling System Works”

Radiator

How important is the pressure cap?

As we just mentioned, the pressure cap is designed to keep the cooling system under pressure. As the coolant heats up, it expands. Because the cap seals the cooling system, this expansion creates pressure.

Increased pressure works in our favor because it increases the boiling point of the coolant. If the coolant were to boil, it would vaporize and would no longer be able to circulate or conduct heat away from the engine.

Therefore, the pressure cap is an indispensible part of the cooling system, and a faulty pressure cap can easily cause the engine to overheat.

Caution: Never open the pressure cap when it is warm or hot. The hot, pressurized coolant could cause severe burns. Wait until it has cooled down!

What’s the other container with coolant in it?

Today’s cars all have some type of coolant reservoir aside from the radiator. It is usually a clear or opaque bottle somewhere under the hood with “min” and “max” marks on the side of it. But what is it for?

As the coolant expands, it eventually may build enough pressure to bypass the pressure cap. If it does this, it needs a place to go.

The reservoir takes on the expanding coolant and holds it until it cools back down and contracts back into the radiator.

Go back to I-learn now and watch the video entitled, “Pressure Caps.”

So what is coolant?In early automobile history, people used water to cool their engines. However, water had several drawbacks—it freezes at 32°F, it boils at 212°F, and it causes the insides of the engine and radiator to rust.

These problems and others prompted the development of “antifreeze,” a chemical that is added to water, creating a mixture with a lower freezing point and a higher boiling point.

This mixture is called coolant. Today’s coolants also prevent corrosion and protect the inside of the cooling system from rust.

On a cold night, if water were to freeze inside your engine and radiator, it would expand and crack your engine block, damaging it beyond repair.

Servicing your cooling system

As a car owner, you’ll be glad to know that the cooling system requires very little maintenance. However, it cannot be neglected, either! Here is a list of things you should do; each of them will be discussed in a subsequent slide:

Check your coolant level regularlyHave your coolant changed at the correct interval

(specified in your owner’s manual)Watch the temperature gauge or warning light on your

dashOccasionally check your hoses and beltsKeep the radiator clean of bugs, leaves & dirt

Check your coolant levelBecause it is so easy, there is no excuse to not check your coolant level each time you open your hood to check your oil. Simply glance at the coolant reservoir and make sure the level is somewhere between the “min” and “max” marks. If it is low, add some coolant and check for leaks. While it is normal for a very small amount of coolant to evaporate over time, if you have to add coolant more than once a year, you probably have a leak that needs to be addressed.

You should not have to open the pressure cap to check the coolant level or add coolant unless there is none in the reservoir. If you see none in the reservoir, it is time to open the pressure cap (if it is not hot) and find out if there is any in the radiator!

Coolant in the radiator

How often should you change your coolant?

The answer to this question is simple: whenever your owner’s manual says that you should. Coolant breaks down over time. It looses its ability to protect from freezing, boiling, and corrosion. If coolant is not changed on time, it can cause expensive damage to the engine, radiator, and other components. No matter how much its costs to change your coolant, it costs less than it would to replace your engine.

There are different types of coolants used in different cars. Because of this, the service interval may range from “every 24,000 miles” to “every 150,000 miles.”

If the wrong coolant is ever added to your system, it may greatly reduce the life expectancy of your coolant—so make sure you use the correct fluid!

It is recommended that you take your car to a professional for cooling system services and flushes. If you choose to do it yourself, remember that roughly half of your coolant is in your radiator and half is in your engine. Draining the radiator alone will only get half of it!

Keep an eye on your instruments!Depending on your car, your dash should have a temperature gauge, a temperature warning light, or both. If you have a gauge, the needle should move to the middle of the gauge (about 210°F) as the car warms up, and never get any higher than this.

If you have a warning light, it should come on when you first turn your key on, then shut off once you start your car. If it ever comes back on while you are driving, the engine is too hot.

If the needle on your gauge ever reaches the “danger zone,” or if your temperature warning light ever comes on while you are driving, pull over and turn the car off immediately. Whatever you do, do not continue to drive the car while the engine is overheating!

Once the engine has cooled down, you may be able to start the car and drive it a little bit further. But only do this if you absolutely have to; if the engine gets too hot, you will be buying a new engine! You should get your car to a repair facility immediately.

TemperatureWarning light

Temperature gauge“Danger Zone”—do not continue to drive

“Danger Zone”—do not continue to drive

Checking Belts and Hoses

It is a good idea to periodically inspect your belts and hoses. The belts keep your water pump and other accessories turning. If it breaks, the pump will not circulate the coolant and the engine will overheat.

Check your belts at each oil change, looking for cracking and chunks that are breaking off. Belts typically need to be changed about every 60,000 miles Cracking

Chunking

Belts

Bulging (feels soft) Leaking

Hoses

Hoses transport the coolant from the engine to the radiator and back. At the same time you are checking your belts, check your hoses for bulging, softness, leaks, or other indications of deterioration. Have them replaced at the first sign of trouble.

Don’t bug me!

Another way you can keep your cooling system operating at its best is to periodically check the radiator to make sure it isn’t plugged with bugs, dirt, leaves, or other debris.

A bug or two is not a problem, but if buildup begins to block airflow through the radiator, the coolant will not be able to cool off enough and the engine may overheat.

When cleaning the radiator, use water, compressed air, or a very soft brush (most auto parts stores sell an inexpensive tool you can use). Using a metal object to clean the radiator may result in punctures and leaks.

Selecting and adding coolantIn the past, all cars used the same antifreeze/coolant. Not today! As mentioned earlier, there are many different types of coolants and they are not all the same. Even coolants that are the same color are not necessarily interchangeable.

The simplest way to determine which type of coolant to use in your car is . . . you guessed it . . . look in your owner’s manual.

Typically, coolant should be checked and added at the reservoir.

Unless you buy it pre-mixed, coolant needs to be mixed with water before it is added to the system. Neither coolant nor water alone has a sufficient freezing or boiling point. However, a proper mixture of both fluids does.

Remember this! For most climates, the recommended ratio of coolant to water is 1:1. This means that the coolant you use should be composed of 50% water and 50% antifreeze, which provides freeze protection down to -35°F.

Engine Lubrication & Cooling Systems Summary

In this lesson we have learned about the indispensible roles of the lubrication and cooling systems in your automobile. Without them, the engine could not operate for very long.

Both of these systems require some periodic maintenance. Whether you choose to do this maintenance yourself or have someone else do it, becoming an educated owner is the first step to extending the life of your engine and car.

Remember: keeping your oil and your coolant full and changed on schedule is the most important thing you can learn from this lesson!