How to Diagnose Your Car If All You Know Is How to Drive It


Does that puddle underneath your car necessitate a trip to the mechanic? Will that rubber smell go away on its own or does it spell major trouble? Is that rattle annoying but harmless, or should you put everything on hold and hightail it to your mechanic?

If these worries sound familiar, you’ve come to the right place. Believe it or not, car diagnosing isn’t limited to mechanics and car enthusiasts. Spotting warning signs early can save a lot of money and inconvenience, so buckle up and let’s get this article on the road!

Make Sure Your Gas Tank Is Always a Quarter-Full

Before anything else, always make sure your tank is 1/4 full. Cars commonly break down because of an empty gas tank. When your car starts sputtering, it’ll usually be too late.

There are two other good reasons to keep your gas tank 1/4 full at all times:

  • If it goes below that, sediments can form and clog it.
  • If you drive a modern car, this also helps keep your fuel pump cool.

Eyes on the Prize

Here’s a quick rundown on the major three things to watch out for.

Problematic Puddles

Puddle under car

Maybe you happened to park where someone also happened to spill something. But in most cases, a puddle under your car isn’t good. It probably means one or more of the fluids in your car is leaking.

This will also save you and your mechanic time and may protect you against ripoffs.

Tire Trouble

Check for a problem in your tire

You’ll probably notice if a big old nail is sticking out of your tire, or if your tire is 100% flat. But you can miss other stuff if you don’t know what to look for. The quarter test is an easy way to test your tires.

Dashboard Warning Lights

Warnings in car dashboard

Always keep an eye on any new dashboard warning light symbols that come on and refuse to go off. Some may look undecipherable, but many will readily indicate the problem. It could be something as simple as time for your oil change.

And keep a simple fault code reader handy to troubleshoot what trouble code may trigger the dreaded ‘check engine light’. A professional scanner can help fix lots of the faults automatically or tell you exactly what to do to solve it. Every driver should know how to use a basic car engine code reader in my opinion.

Alternatively, it could mean a serious problem. If you know what the overheating symbol is, for instance, you could save yourself time and money by pulling over as soon as you can and calling your mechanic.

Perk Up Those Ears – Car Noise Diagnosis (10 Sounds & Meaning)

Even if you’re listening to a hilarious Car Talk episode, pause it if you hear an unusual sound coming from your car.

Harmless noises typically develop and disappear. They’re usually not ear-piercing either. Serious sounds can be easy or extremely hard to trace anyway. Here are the 10 most telling car sounds and what they can mean.

1. Squealing

Is the squealing coming from under the hood? Don’t fret. It’s probably an accessory belt slipping on a pulley. This is usually fixed easily and fast.

Does the squealing come from the wheels when you brake? This could mean a brake issue, such as worn-out brake pads.

Is the squealing coming from your tires? Ease up on the accelerator and  check your tire pressure.

2. Clunking

Do you hear the clunking with the brakes? You need to take your car to the mechanic immediately: This could mean damage or wear to your brake discs, pads, or calipers.

Do you only hear the clunking over bumps? Some part of the exhaust might be loose or there might be something wrong with your suspension.

Does the clunking happen when you’re turning corners? Your mechanic might need to look at your wheels, tires, wheel bearings, or steering.

3. Hissing

Does the hissing come from under the hood? What you’re hearing could be fluid leaking onto a hot surface, like the engine or exhaust manifold. Take your car to the mechanic immediately.

Does the hissing only happen when you accelerate? One of the hoses around the air intake might be leaking.

4. Clicking

If you hear a clicking sound under the hood, you could be low on oil. It could also be a valve train problem in an older car.

If you’re behind on service, your engine could simply be worn out.

5. Rattling

Rattling usually means something is loose. It could also mean a foreign body lodged underneath. Take your car to your mechanic as soon as possible.

6. Grinding/Whirring

Does the grinding seem to be concentrated in the gearbox? If you drive a manual, this probably means you have clutch issues. Otherwise, you’re probably looking at problems with the clutch thrust bearing or with the transmission shafts and gears.

Is the grinding coming from under the car? Your gearbox may be low on oil. Alternatively, you might have wheel bearing or CV joint issues.

If the grinding happens when you brake, your brake pads may be worn. This means that the brake-pad metal backing will keep grinding against your brake disc rotors.

See your mechanic immediately. Until the problem is fixed, your brakes will be inefficient and the metal-on-metal friction will wreck your discs.

7. Roaring

Roaring is that noisy sound from your exhaust when you accelerate. Generally it means your exhaust system is falling apart and the muffler is no longer working.

You can still drive and the rest of the car will probably be safe from any damage. You should still get it checked out. An exhaust issue can let exhaust emissions into the car, which is extremely dangerous for you.

8. Whistling

If you hear whistling under the hood, your engine may have a vacuum leak from one of air-intake hoses. This is hard to trace but easy to repair.

9. Banging

A backfire from the exhaust pipe means un-burned fuel ignited in the tailpipe. It can mean an exhaust or vacuum leak or a catalytic converter issue. If you drive an older car, the engine might be out of tune.

A bang from the hood usually means engine trouble. You might be looking at worn spark plugs, a blocked fuel filter, or a broken catalytic converter.

10. Knocking

Knocking is usually serious. It can also happen if your engine is poorly tuned or if you’re using the wrong fuel. This usually happens when you accelerate and it’s closer to a ping than a full-on knock.

Weird Whiffs – Diagnose Car Smells

Weird smells can be one of the fastest ways to troubleshoot your car. Next time you smell a weird odor in your car, don’t reach out for that car freshener. Take a focused sniff and try to place it.

The fluids in your car coupled with its engine and all its hot metal parts can make for some super-interesting smells. Take a look at the eight deadly smells you need to be on the lookout for.

1. Syrup/Sweet Smell

Can you smell something sweet when the car is running or immediately after turning it off? It could be a coolant leak. The leak source may be your radiator, one of your hoses, or your car’s heating system.

This is a serious issue that needs to be looked at immediately. Ignoring it can dry out your radiator or ruin your heating system.

2. Sulfur/Rotten Eggs Smell

Your fuel contains sulfur. If everything is working fine, that sulfur should turn into odorless sulfur oxide. If you can smell rotten eggs, it can mean problems with your converter or filtering layers.

Alternatively, it could mean a broken fuel pressure regulator or an engine that is running too hot.

3. Burning Rubber

A burning rubber smell can mean a burning clutch. It can also mean an oil leak onto the engine. You can also smell rubber if one of the various engine belts fails and heats up.

Regardless of the reason, take your car to your mechanic as soon as possible. Ignoring this can damage the engine.

4. Burning Carpet

First, make sure that you’re not driving with your handbrake on. If it’s disengaged and you can still smell burning carpet, this could mean brake issues. One of your brakes may be dragging.

5. Smoke/Burning Paper

Do you smell burning when you brake? If so, ease up on your brakes. You’re probably making them overheat. You don’t need brakes every time you downshift one or two gears.

If you drive a manual-transmission car, you can smell smoke if you have a worn clutch.

Finally, this can also happen if a fluid leaks and burns on the engine or another hot surface. Wait until your car cools down and check the engine and around the gaskets for any damp spots.

6. Gasoline

You’ll smell gasoline if you tend to let gas dribble out when you’re filling up the car. A more serious reason is a leak in the fuel injection line or the vent hose.

This needs to be checked immediately. It’s serious enough that you shouldn’t light anything up around your car until your mechanic says you’re good to go.

7. Hot Oil

If you smell hot oil, then oil is probably leaking onto your exhaust manifold. If there’s a puddle under your car, the culprit is most likely a leak in your crankshaft. If there’s smoke coming out of the exhaust, one of your valve covers is probably leaking.

8. Musty/Moldy/Old Socks

Does this odor assault your nose when you turn on the air conditioning? This may mean mold and mildew in the air-conditioner evaporator, an air vent, or in the carpet.

This needs to be fixed immediately. Mold is a dangerous allergen that can cause symptoms as serious as extreme asthma. Until you can get to your mechanic, try shutting off the air conditioning and running the fan with the vents open.

Feel It Out – Diagnosing Car Vibrations

You can detect some problems with the car through vibrations. They can be strong enough to shake your car quite violently. They may also cause your steering wheel or pedals to jump.

Observe and catalogue the vibrations. When do they happen? Do they get worse with speed or do they happen before you’ve even moved your car? Are they strongest in the steering wheel or seat? Do they come with any noises?

Here are the major types of vibrations and what could be causing them.

1. Vibrations All Over Your Car

Does the vibration seem to happen as long as the engine’s running, whether the car is moving or not? Is there any noise along with the vibration?

Your culprit could be the engine and transmission. If you have a particularly old car, it could be an out-of-whack radiator fan.

2. Vibrations in Your Steering Wheel

If your steering wheel is the only part you can feel vibrating, you may be looking at suspension or joint wear. A quick trip to the mechanic can fix whatever is wrong with your car’s ball joints and steering wheel components.

3. Vibrations in Your Steering Wheel and Brake Pedal

If both your steering wheel and your brake pedal shake, your brake rotors may be damaged or worn. This is a serious safety issue. You need to have your mechanic inspect your brake system to ensure your safety.

Car Diagnosing Video

Take Notes of Car Diagnosing

When did the weird sound, smell, light, or sensation start? Does it only happen at high speed or when your car is in idle? Is it always accompanied by the same thing, such as going over a bump? Keep a log of everything going on.

Also keep another log of all the changes you make. This way you know when your oil change is due, for instance. This will also help your mechanic zoom in on the problem.

You’re Never Too Old for Class

Although the tips in this article will go a long way to help you in diagnosing car problems, nothing can replace good old education.

At the very least, you should know the names of your car parts. Get the factory service manual for your vehicle. It usually contains a diagram of the parts, an explanation of how your car operates, and a step-by-step troubleshooting guide.

If research and reading up is your thing, you can download the ASE study guides. They’ll teach you basic information from brakes to fuel injection.

If you have more time, the very best thing would be to go to a class. You can take online classes that come with videos. You can also go the more old-fashioned way and go to a brick-and-mortar classroom.

You can sign up for classes at your local community college or adult education center. Nothing can beat the hands-on experience you’ll get learning on actual cars.

Youtube and Podcasts of Diagnosing Cars

Google your car’s symptoms. There are tons of podcasts and Youtube videos by mechanics and car repair enthusiasts that aim to teach and help.


Identifying a problem can help your mechanic fix it early. They’ll have better odds of nipping it in the bud, saving you money, time, and a ton of inconvenience. Your girl will run more smoothly and age well.

Even better, you can rest easy knowing your mechanic won’t rip you off because you’re just another clueless driver. And if you’re stranded on a long empty highway? If the problem is easily fixed, basic car diagnosing skills may even keep you safe.

Car Diagnosing
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