Check Under the Hood

Checking fluids and connections under the hood of your car can save you hundreds of dollars in repairs.

Checking fluids and connections under the hood of your car can save you hundreds of dollars in repairs.

Car maintenance begins at the gas pump. It continues as you check under the hood of your car either at the gas station or in your driveway. You can easily check coolant, check washer fluid, check oil level, check transmission fluid, check battery fluid, check power steering fluid, check the battery and check other connections. You can save hundreds of dollar in repairs just by doing simple car engine checks and maintenance. The Fix-It Club can show you how.

Fix-It Tip

About the only tool you’ll need is a shop rag or old washcloth to keep your hands clean. If you prefer, you can also wear surgical gloves to ensure that oil and gunk won’t ruin your manicure. All of these checks are done at the front of your car, so pop the hood and let’s get started.

You learned how to open the hood in the Car Maintenance Fix-It Guide. As a refresher, most modern cars have a hood release located near the driver. Once pulled, you can move to the front of the car and reach below the slightly-opened hood and push or pull the hood release. Then lift the hood and, if it doesn’t stay up by itself, find and place the support rod to hold the hood.

Following are the various checks that most cars have in common. Your car may vary. I recommend that you make these checks in an easy-to-remember order to cut time and to make sure everything gets checked. You can look at the engine compartment from the front as a clock and start your checks at 12 or 6, or you can always start on the driver’s side of the car and work toward the passenger’s side. Whatever works for you. What’s important is time-saving consistency.

It is important that you check under the hood on a regular schedule to make sure that the car’s vital fluids (oil, coolant, power steering, brake, and transmission) are within recommended operating ranges — not too much and not too little — and that some critical parts are in good condition. You really don’t have to get dirty.

Fix-It Tip

You can learn a lot about your car by taking a good look at the driveway and/or the garage floor. For example, a puddle of water is condensation from the air conditioner (that’s okay). A yellow or yellowish-green puddle is probably leaking coolant. A reddish puddle is usually automatic transmission fluid. A puddle of black liquid can mean an engine oil leak, a manual transmission leak, or a differential lubricant leak, depending on where under the car it is.

Check Coolant Level

Add coolant as needed to the coolant reservoir, not the radiator.

Add coolant as needed to the coolant reservoir, not the radiator.

As you check under the hood of your car, the first check many folks make is radiator coolant level. On some cars this is easier than on others. The radiator is located at the front of the engine compartment just behind the hood latch. Newer engines made of aluminum don’t need as large of a radiator as older engines so modern radiators are relatively small. Because they are smaller, it’s even more important to make sure that the engine has sufficient coolant. An aluminum engine without coolant can destroy itself in minutes.

Note that I didn’t say “water” but “coolant”; there’s a difference. Coolant for most cars is a mixture of half water and half antifreeze. (The car’s owner’s manual will be more specific.) In colder climates, coolant may be all antifreeze.

Many cars have a plastic coolant reserve tank at one side or the other of the radiator. If so, there probably are marks on the side of the tank indicating FULL or MAX and LOW or MIN. If the coolant level is between these two lines, add coolant until the level is at the FULL or MAX line. Don’t overfill.

If the coolant is below the LOW or MIN line, or your car doesn’t have a coolant reserve tank, carefully remove the radiator’s cap and slowly fill the radiator with coolant. (Filling slowly allows air in the radiator to escape.) Most radiator caps are turned counter-clockwise to remove and clockwise to tighten. Once full, reinstall the radiator cap and, if needed, fill the reserve tank.

Finally, wipe up any excess coolant as it can damage some paint finishes. In addition, coolant is toxic, especially to animals.

Car Alarm

Be very careful when removing the radiator cap because the hot coolant is under pressure and can scald your skin. Radiator caps can be loosened in steps, turning slightly to release pressure without blowing the cap off. It’s safer to take an extra 15 minutes or more and let the radiator cool down before opening the cap.

Check Oil Level

Add oil to the engine using a funnel for less mess.

Add oil to the engine using a funnel for less mess.

Oil is your engine’s blood supply. Newer and well-maintained engines don’t use up or leak oil, so checking oil means testing it for grit and water — two things you don’t want running around in your engine. Older engines may burn oil (oil actually gets inside the cylinder and explodes with the gas mixture!) and must be replaced. So you’ll also be checking to make sure that the oil level is FULL.

Start by finding your car’s oil measurement device, called a dip stick. It’s so called because it is a long, slender metal stick with its head at the top of the engine and its bottom tip in the oil that coagulates at the bottom of the engine. By pulling the dipstick out of the engine and inspecting the tip you can see the level of oil in the engine.

So it makes sense that you want to make sure your car is relatively level when you check its oil. And the car’s engine should be off for a few minutes so that the circulated oil drains down into the bottom of the engine (called the oil pan). Also, make sure the dipstick has been pushed down as far as it will go in its tube so it gives an accurate reading of the depth of the oil in the pan.

It actually takes longer to read about checking oil than doing it. Lift the stick from its tube and visually check where the top edge of the oil is. If you have any doubt, wipe the dip stick clean with a rag and reinsert the stick all the way into the tube for a moment and withdraw to visually verify. (Check the car’s owner’s manual if you’re not sure where the FULL line is.)

Next, wipe some of the oil on a bare or gloved finger and rub it between a finger and thumb to feel whether it is gritty. Also, look at the oil to see if it looks like some water is in it. Oil and water don’t mix so the water should be obvious. Finally, hold the end of the dip stick or your oily fingers up to your nose and smell the oil. If it smells burnt it probably is, indicating its time for an oil change.

Fix-It Tip

Remember to keep the dipstick’s handle higher than the tip you’re reading. Otherwise the oil will run up the stick and give you a false reading.

Note that as you perform your car’s maintenance on a regular schedule, you won’t have to do the look-rub-sniff test to find out how the oil is holding up. You’ll be changing it before there are oil problems. Even so, periodically inspecting your oil between changes is a good way to read your engine’s condition, as you will learn in other sections of this website.

Another note: If buying a used car, the look-rub-sniff test can help you determine if the car’s oil has been properly maintained. It’s also a good indication of how the car has been cared for overall.

Check Transmission Fluid Level

Automatic transmission’s need fluid, too. As you check under the hood of your car, make sure the car is parked on a level spot (for the same reason as when you check engine oil level). Then find the automatic transmission fluid dip stick, pull it out, and wipe it with a clean cloth. Insert the dip stick all the way into the transmission securely, then withdraw it to visually check the fluid level. It should be between the upper and lower marks.

If the fluid level is low, replace it to the FULL mark with automatic transmission fluid (ATF) approved by the manufacturer.

Most manual transmissions don’t have a handy-dandy dip stick. Instead, they are checked from underneath the car. Fortunately, fluid level doesn’t have to be checked often.

Car Words

Automatic transmission fluid (ATF) is a thin petroleum designed to freely flow through the transmission’s hydraulic components. It also contains additives to keep it clean and extend its life.

Check Power Steering and Brake Fluids Levels

Modern cars have other fluids that are nearly as important and just about as easy to check. Steering systems use a special hydraulic fluid that makes steering easier. Brakes use a different type of hydraulic fluid that magnifies your foot’s pressure on the brake pedal to make brakes at all four wheels slow your car down.

Steering and brake fluids are not interchangeable. In fact, you should only use the exact type of fluid recommended by the manufacturer when replacing fluids (check the owner’s manual). For example, brake fluids come in at least three specifications: DOT 3, DOT 4, and DOT 5. (DOT stands for U.S. Department of Transportation.) If your car’s manufacturer calls for DOT 3 brake fluid, do not use DOT 4 or DOT 5 unless the manufacturer says you can Why? Because these hydraulic fluids have different additives that work well in one type of brake, but can actually destroy another. Also, brake fluid is relatively cheap so don’t use it from a can that’s been open more than a year.

Checking steering fluid is relatively easy. Most cars that use steering fluid provide a well-marked tank in the engine compartment somewhere on the driver’s side of the car. In fact, many are translucent with a FULL line that can be read without opening the top. Alternately, simply twist the steering fluid cap off and use the short dip stick attached to the cap to check the fluid’s level. If you’re not comfortable with checking or replacing the steering fluid, ask a trusted mechanic or full-service station attendant to do so.

Brake fluid is held in a special reservoir clearly marked BRAKE FLUID. Do not refill with anything except the manufacturer's recommended brake fluid.

Brake fluid is held in a special reservoir clearly marked BRAKE FLUID. Do not refill with anything except the manufacturer’s recommended brake fluid.

Brake fluid is also important to your car’s well-being. To check fluid level, you may need to remove the master brake cylinder’s top and visually check it. Many master cylinders have a reservoir similar to that for the steering system. (Be careful not to get them confused and add the wrong fluid!) Others have a metal cap with a pressure clip that most be carefully pried off with a screwdriver to check the level. Again, if you’re not comfortable doing this, hire someone who is and watch them. Or refer to the car’s owner’s manual or service manual for specific instructions.

Some cars have a fluid for the manual transmission’s clutch system. It, too, is a hydraulic fluid used in a booster that makes depressing the clutch pedal easier. If your car is so equipped, look for a small reservoir clearly marked for CLUTCH FLUID and remove the cap to look for a fluid level indicator. The cap (or owner’s manual) will tell you what fluid to use when refilling.

 Check Washer Fluid Level

Washer fluid is checked and filled in a reservoir marked with a windshield wiper diagram.

Washer fluid is checked and filled in a reservoir marked with a windshield wiper diagram.

Here’s another easy thing to check under the hood of your car. The windshield washer can spray soapy water on your car’s windshield to help keep it clean. The washer gets the fluid from a reservoir in the engine compartment, clearly marked. In fact, most are easy to find and to refill.

To refill, remove the reservoir cap and pour windshield washer fluid in the tank until the level is near the top. The fluid is water, some soap, and maybe some alcohol or other chemical to keep the mixture from freezing when it’s cold outside. Alternately, you can use plain water when it’s warmer.

 Check the Battery

Once a month, check the connections at your car’s battery to make sure they are clean and well-connected. If the battery isn’t maintenance-free (most are today), you may need to check the level of distilled water in the battery cells.

Make sure battery post connections are clean and tight.

Make sure battery post connections are clean and tight.

This is another job that takes longer to read about than to do. Once familiar with it, checking battery connections will take just a few seconds. All you’re doing is carefully wiggling the battery cables at the two terminals. Because the battery is full of acid and electricity, treat it with the proper respect and don’t try touching the terminals without gloves—or at least a clean rag—between you and the battery. If the terminals are loose, carefully tighten them with the proper size wrench.

If the terminals have a white or light-colored power on them, carefully clean the terminals with a brush or rag, being very cautious as the dust is corrosive. If you’re not comfortable doing this, take your car to a battery shop or a trusted mechanic. If you want to do it yourself, unloosen the terminals and use a battery brush to clean the terminals and posts. Then apply a battery gel or washers that minimize corrosion.

Note: Disconnecting your car’s battery may require that you reset a security code. Read the owner’s manual for specifics before disconnecting the battery.

Car Alarm

Many jobs around your car require that you disconnect the negative terminal on your car’s battery for safety. On many cars, doing so may require that you reset a security code. Read the owner’s manual for specifics beforedisconnecting the battery. Also, be aware that some car computers will automatically clear diagnostics codes from memory if the battery is disconnected.

Check Engine Connections

Check coolant hose connections to make sure they are tight and squeeze the hose (if the engine is cool) to make sure they are in good condition.

Check coolant hose connections to make sure they are tight and squeeze the hose (if the engine is cool) to make sure they are in good condition.

There are dozens of other parts in the engine compartment as you check under the hood to make sure they are solidly connected. As with other tasks, once you’re familiar with things in the compartment it will take just a few seconds to wiggle and make sure everything is well connected.

Here are some suggestions for typical cars:

  • Spark plug wires
  • Electric wire connections
  • Engine belts
  • Radiator hoses

The Fix-It Club knows how to check under the hood of your car to reduce repair bills.