Burning Smell in car

Usually, when you get a burning smell from your car the first thing you think is that’s overheating. With a panicked pulse, you look down at the dashboard, scolding yourself for having taken your eyes off the engine temp gauge, while trying not to worry about where you can pull over to avoid catastrophe.

Though what happens when you get that burning smell wafting through the vents and windows, but the engine temperature gauge reads normal? What then?

If your mind is reeling wondering what’s causing a burning smell from your car but not overheating, you need to pay keen attention to what the other symptoms are telling you. The truth is there are a lot of mechanical faults big and small that can cause a burning smell without overheating. Understanding them and what you might be able to do about them can save you a lot of worries, and maybe even some money.

Top Reasons for a Burning Smell From a Car Without Overheating

Different faults in the engine and exhaust system can cause different types of burning smells in the cab of the car or outside. The unique odor of the burning smell, where it’s strongest, and other symptoms of a problem will help you dial in the cause.

  • A Coolant Leak (Sweet Smell)
  • Mouse Nest Near the Heater Core (Sickening Sweet Smell of Urine)
  • Short Circuited Wires (Burning Plastic)
  • Engine Oil Seal Failure (Petroleum Vapors)
  • A Bad or Failing Alternator (Burning Wires)
  • A Loose Serpentine Belt (Burning Rubber)
  • A Minor Exhaust Leak (Sulfer or Rotten Eggs)
  • A Burnt-Out Blower Fan Motor (Sweet Smell with Burning Plastic)
  • Seized Brake Caliper (Burning Hair)
  • Fluid Leak (Odor Varies)
  • Worn Flywheel or Burned-Out Clutch (Sulfur and Burning Wires)
  • Old Oil (Petroleum Vapor)
  • Tire Wearing on the Wheel Well (Burning Rubber)
  • Burned-Out Wheel Bearings (Burning Wires and Old Oil)
  • A Bad or Clogged Catalytic Converter (Sulfur or Rotten Eggs)

1. A Coolant Leak

A Coolant Leak

A sweet smell from a minor coolant leak from a hole in a radiator hose a failed gasket, or a stuck-open thermostat often gives off a little steam as well. Gravity might pull the leaking coolant down onto the hot engine or let it drip onto the hot exhaust manifold. Though a coolant leak can annoyingly run along a hose, pipe, or wire to deposit far away from the actual leak.

How to Troubleshoot & Fix a Coolant Leak

To find a coolant leak, it helps to let the engine heat up. This will open the thermostat and get the coolant flowing through the system until it creates an active leak. Once you notice the smell getting stronger, pop the hood and look for any white steam coming off the engine bay or the exhaust manifold.

This will tell you where the coolant is dripping onto. You might even be able to see the drops falling. It might even make a small puddle or spatter marks under the car. Make sure to look at the thermostat, which is usually located near the top of the radiator, as well as the radiator cap. Just don’t touch any of the leaking coolant with your bare hands as it will likely still be very hot.

If it’s a minor leak, it might be easy to fix. This could be something as simple as replacing a pipe clamp, or replacing a crumbled, leaky radiator hose.

If the coolant leak is caused by a stuck-open thermostat, you’ll likely see little bubbles around the thermostat housing when the engine is hot.

You can usually replace a bad thermostat yourself for less than $75.

If the coolant leak is coming from a bad radiator cap, the cap will need to be replaced, which costs around $25.

2. Mouse Nest Near the Heater Core

OBS Ford F450 Heater Core Mouse Nest

A sickeningly sweet odor, of mouse urine with disgusting whiffs of burning hair is indicative of a mouse nest in the heater core. You likely notice it when you turn your cab heater on, and it will get stronger the hotter it gets. This is more likely to happen in winter when mice and other rodents are looking for warm places to raise their pups (babies).

You might also notice buzzing sounds from fouled wiring and clogged blower fans. If the mice chew their way into the vent system, you might also notice a sickening sweet musty odor of rodent urine along with the burning smell.

How to Troubleshoot & Fix a Mouse Nest Near the Heater Core

Depending on the model, a professional mechanic will need to either access the heater core via the engine bay or through the dash. They’ll have to pull out the nest as well as fix any other components of the heater core and vent system that the rodents damaged.

The cost to have a mouse nest removed from the heater core ranges from $125 to $500. The model of the car and the damage the mice caused will greatly affect the price.

In the future, you can prevent or at least reduce the risk of a rodent problem in your car by scattering moth balls under your parking spot every 4 to 6 weeks.

3. Short Circuited Wires

Short Circuited Wires

A burning smell of melting plastic and hot metal is usually a sign of short-circuited wires. This could be from fuses or wires inside the cab. Though it’s more likely to come from wires in the engine bay, then migrate through your vents to your nose.

Short-circuited wires are more common with older cars that may have had an animal like a cat or a mouse nest get inside. Though it’s also possible for short, circuited wires to happen as a factory defect in a new car that’s just been driven off the lot.

Finding where the short, circuited wires are can feel like you’re chasing gremlins. The faulty wires causing the burning smell can be just about anywhere.

How to Troubleshoot & Fix Short Circuited Wires

The first step is to inspect all the fuses and relays in the cab fuse panel as well as the engine bay fuses. If you smell the burning odor is stronger and/or you see a burned-out fuse it will help you dial in where the electrical fault is.

You can then use the owner’s manual or the repair guide for your make and model to troubleshoot which wires might have a fault.

Most Common Places Where Short-Circuited Wires Occur

  • Near the battery
  • Leading to the engine bay’s relay/fuse box
  • Wiring loom going to the front doors
  • Near or behind an aftermarket radio deck
  • Spark plug wires
  • The coil pack in the engine bay

If you can find the short-circuited wires yourself, and the damage to the wire looks simple, such as damaged wire coating from a stray cat that got in the engine bay, you might be able to fix it yourself for less than $20.

If the short-circuited wires are in a hard-to-reach area, such as passing through the driver’s side wiring loom, or a damaged spark plug wire, then you probably need a mechanic to handle the repair.

The cost to have a professional mechanic repair short-circuited wires can range from $75 to $400. It all depends on how much labor time they have to put into accessing the damaged wire and repairing any other damage that might have been caused by electrical arcing.

4. Engine Oil Seal Failure

Engine Oil Seal Failure

A burning smell with a distinctive petroleum oil odor is a disturbing sign of a failing oil seal. In the early stages of an oil seal failure, the oil leaks out or seeps out in a small amount. It can then drip onto hot parts components in the engine bay or fall on lower components of the exhaust system.

Engine oil seal failures that create a burning smell without overheating can occur with time in an older vehicle. Though frequently running the engine hot, and or having too much oil in the oil pan after an oil change can lead to premature oil seal failure.

How to Troubleshoot & Fix an Engine Oil Seal Failure

The burning smell of an oil leak like this has an acrid odor, mixed with the smell of petroleum. You’ll often notice oil drops on your garage floor or your office parking spot. With a rear main oil seal, you’ll see the drops closer to the engine’s firewall.

You’ll also be able to see the oil dripping under the car when the engine is running and then shortly stops when you turn the engine off.

As an engine oil seal inevitably gets worse, the volume of oil it expels will increase dramatically. You’ll have larger and larger oil spots, and you’ll notice a considerable drop in oil pressure on your dash gauge. Not to mention the dipstick always shows that the engine is low on oil, even if you top up the oil pan.

The cost to have a mechanic replace an engine oil seal can range from $175 to as much as $1,500. With the real-world average landing right around $450.

5. A Bad or Failing Alternator

A Bad or Failing Alternator

A burning smell like hot wires and burning plastic might be a sign that your alternator has failing bushings. Your car’s alternator is always running when the engine is running, and you’re likely to notice it more when the engine revs.

As time goes on the brushes and winding insulation can wear down. This is even more likely to be a problem below 100,000 miles if the alternator or the engine bay has frequently been running hot.

How to Troubleshoot and Fix a Bad Alternator

You can easily test to see if a bad alternator is causing the burning smell from your car with a multimeter or voltmeter. With the engine off test the battery with the multimeter or voltmeter. It should read around 12.5 Volts if the alternator is charging it properly.

Then you can use a voltmeter or multimeter to test the alternator with the following steps.

  • Step One: Turn the car off and set the multimeter to DCV Volts above 15.
  • Step Two: Make sure the alternator’s positive and negative terminals are clean. If they have corrosion, clean them with a dry electronics cleaner spray like a MAF sensor cleaner.
  • Step Three: Connect the multimeter’s black cable to the negative terminal and the red cable to the positive terminal. A good alternator should give you a reading of around 12.5 Volts.
  • Step Four: Start the engine with the leads still connected to the suspect alternator’s terminals. The reading on the meter should quickly jump up from 14.2 to 14.7.
  • Step Five: Turn on lights and as many other electronics and watch the reading on the meter. The reading should drop to around 13 Volts.
  • Step Six: Turn the engine off, wait 2 to 3 minutes, and check the alternator again. It should give you a reading of around 12.6 Volts.

If any of these readings are off, then chances are good that you have a bad alternator, and most likely found the cause of the burning smell from your car without overheating.

You can usually replace an alternator yourself for the part cost which ranges from $125 to $250 depending on the size and model.

The cost of having a mechanic replace your alternator ranges from $225 to $400.

6. A Loose Serpentine Belt

A Loose Serpentine Belt

A burning rubber odor that builds up as you drive, and then gets worse when you’re sitting at idle is a possible sign of a loose serpentine belt. You might even hear a whining or slapping sound in the engine bay right before the burned rubber odor wafts through your vents.

At the same time, your car’s serpentine belt uses a small portion of the power produced by the engine to power other components like the alternator, power steering pump, water pump, and the A/C compressor, via a series of interlinked pulleys. The serpentine belt maintains sufficient taught tension thanks to a mastering tensioner pulley.

If the tensioner pulley or any other pulley in the belt-driven engine components becomes misaligned or damaged or the tensioner pulley is set wrong, the serpentine belt can start to slip. This is usually a problem that worsens, producing a burning rubber smell from the car without immediately overheating.

How to Troubleshoot & Fix a Loose Serpentine Belt

A bad serpentine belt that causes a burning smell from the car without overheating will often give off screeching sounds at startup or when accelerating. If the belt is made from reinforced rubber, it might also show signs of fraying, cracking, and splitting.

You’ll likely also notice problems with engine components like the alternator charging poorly, or weak power steering. If the serpentine belt is slipping over the water pump pulley, the engine might run hot while making a burning smell, but not overheating.

If the serpentine belt itself is worn out, and that’s causing it to slip, you can usually replace the belt yourself. A slipping serpentine belt that causes a burning smell is usually due to a misaligned or damaged pulley or a problem with the tensioner pulley.

The cost to have a tensioner pulley or other pulley replaced can range from $150 to $300.

Most of the cost is from the part, and only $75 to $100 for labor.

7. A Minor Exhaust Leak

A Minor Exhaust Leak

A sulfurous, rotten egg odor is often a sign of a leak in the car’s exhaust manifold, a cracked catalytic converter, or a rusted muffler or tailpipe can easily cause a burning smell from a car without overheating.

The odor will usually get stronger over time when you’re sitting at idle. Then it might suddenly vanish when you drive off, leaving the bulk of the leaking exhaust vapors behind in the breeze.

The real worry here is that while you might smell burning and exhaust fumes in trace amounts, dangerous carbon monoxide gas is odorless and might be building up in your car as you drive.

If you have reason to believe that an exhaust leak is causing burning smells in your car, it’s best to drive with the window rolled down until you can properly fix it.

How to Troubleshoot & Fix a Minor Exhaust Leak

Many times an exhaust leak from the exhaust manifold that causes a burning smell without overheating will make a ticking sound when the engine is running. The three most common places where an exhaust leak might develop are:

The mounting surface gasket that joins the exhaust manifold to the engine

The gasket where the exhaust manifold connects to the downpipe

Where the downpipe attaches to the catalytic converter

If the exhaust leak is due to a problem with the tailpipe, muffler, or a crack in the catalytic converter case itself, you will likely notice wisps of exhaust under the car when the engine is running.

Fixing a Minor Exhaust System Leak Yourself

If you find a minor leak on your tailpipe or muffler you might be able to “Patch” it with epoxy bonding tape. Though this is just a short-term fix to buy you time for the more serious repair bill.

Fixing a more major exhaust leak that causes a burning smell inside the car usually requires a professional mechanic to weld the leak or completely replace the leaking component.

The cost to have a mechanic handle the repair can range from $125 for something like a failed gasket replacement in the exhaust manifold to as much as $500 for a major repair welding a damaged exhaust system component.

If a major component like the catalytic converter is damaged or clogged, the cost can range from $900 to $2,500.

8. A Burnt-Out Blower Fan Motor

A Burnt-Out Blower Fan Motor

A melting or burning plastic odor could be a sign of a burnt-out blower motor fan. When this happens, the air coming out of your vents will be weak or completely non-existent. You might even notice little tendrils of whiteish-blue smoke coming out of the upper dash vents.

A lot of times these odors are immediately preceded by a strange ticking or growling noise as the fan blades make contact with the melting plastic housing.

Troubleshooting & Fixing a Burnt-Out Blower Motor Fan

If you have a burning smell from the car but not overheating with poor air passing out of the vents, plastic aromas, and possibly white whisps of smoke, your blower motor fan is likely toast. Pulling the fuse to prevent electricity from it will help prevent the problem from getting worse and might even save you from a tragic electrical fire!

You usually need a mechanic to handle replacing a burnt-out blower motor fan. There are usually a lot of other components in the way, like the heater core, and you’ll need a set of professionally trained eyes to spot any other damage in the car’s HVAC system.

The cost to have a mechanic replace a burnt-out blower motor fan ranges from $275 to $450. Most of this cost is labor time to safely remove the part and all other components that were in the way.

9. Seized Brake Caliper

Seized Brake Caliper

A burning smell like burned hair coming from the car without the engine overheating could be related to a seized brake caliper making prolonged contact with a warped rotor. In a case like this, you usually hear a grinding noise coming from one corner of the car when you step on the brakes.

You might also hear a hissing, rasping, or grinding noise when you start off again from a stop. This is a sign that the seized brake caliper is getting so hot on the rotor that it’s temporarily making a weak tack weld between the two surfaces.

If you have a manual parking brake and forgot to release it after being parked on a hill, it could also cause a burning smell and grinding noise. Though you will notice this odor coming from the rear brakes. Hopefully, if you catch it early enough, you can release the parking brake before it causes any serious damage.

Troubleshooting & Fixing a Seized Brake Caliper

A burning smell from a car without overheating caused by a seized caliper is a serious brake failure and the car is likely unsafe to drive. You will likely also notice grinding noises, a vibrating brake pedal, and the car pulling to one side when braking.

If you have an automotive infrared thermometer you can confirm a brake problem by setting the laser light point on the caliper or the rotor. If you are getting a temperature exceeding 400 degrees Fahrenheit, then you likely found the cause of the burning smell.

If the seized brake caliper is due to a mechanical malfunction, severe rusting, or the caliper is badly damaged due to prolonged grinding on the rotor, then the entire caliper will need to be replaced.

The cost to have a mechanic replace the badly seized brake caliper ranges from $250 to $450.

A lot of times when seized calipers are the cause of brakes making a grinding noise though the caliper damages or warps the brake rotors.

10. A Fluid Leak

A Fluid Leak

All kinds of fluid leaks can cause a burning smell from the car without overheating. These can range in severity from something as simple as oil dripping off the dipstick and landing on the exhaust manifold, to something as severe as coolant spattering on the engine block from a cracked cylinder head.

The most mundane and common of fluid leaks is when you or a rapid lube shop change the engine oil and a few drops miss the hole, dribbling down onto the engine or components of the exhaust manifold. If this is the case, then the burning smell usually goes away in 15 to 20 minutes of driving.

Sometimes a loose coolant hose or a stuck open thermostat can let coolant out. In a scenario like this, the burning smell might intensify and be even stronger when you’re stopped at the lights.

How to Troubleshoot & Fix a Fluid Leak

Determining if the burning smell from your car is caused by a fluid leak starts with a meticulous visual inspection of the engine bay. Focus on the exhaust manifold and the engine block. These are the hottest things and drips from a fluid leak will leave stains that you can trace back to the source.

Then also take the time to check all the engine fluids and the transmission fluid. If one is low, then you know what system to focus on.

Some minor fluid leaks like a loose radiator hose can be a small, inexpensive repair if it’s caught early. Other fluid leaks, like a failed front main oil seal, can cost hundreds of dollars.

11. Worn Flywheel or Burned-Out Clutch

Worn Flywheel or Burned-Out Clutch

A rotten eggs smell that is strongest under the hood, could be a sign of a burned-out or slipping clutch. It might even give off whisps of white smoke that you can notice creeping out of the gaps in the car’s hood.

In a case like this, the slipping clutch creates significant friction, which can start to damage the flywheel. It’s important to stop driving the car, and let it cool down before proceeding.

How to Troubleshoot & Fix a Burned-Out Clutch

If a burned-out clutch is causing the burning smell from your car, you’ll likely also notice slipping, grinding noises when trying to change gears, puffs of sulfurous smoke, and perhaps even a sticky clutch pedal. At this point, the only option is to have the clutch replaced.

Replacing a clutch is usually beyond what a DIY mechanic can do. There’s also the concern that the clutch has damaged the flywheel, which would then also need to be replaced.

The cost to have a mechanic replace a burned-out clutch ranges from $550 to $900.

The cost to have a mechanic replace a damaged flywheel ranges from $500 to $1,000. Though about $300 of this is the part cost.

The cost to replace both a burned-out clutch and a flywheel will run you around $900 to $1,800.

12. Old Oil

Old Oil

If you’ve had your car in storage for a while, the old oil can degrade causing a burning smell from the car without overheating. This is also a possibility if you drive one car in the winter and another one in the summer.

When oil sits for a long time it starts to break down and becomes exothermic. This will give you a burning smell that clearly smells like burning oil, with a waft of melted wiring.

How to Troubleshoot & Fix Old Oil

If your car has sat for more than two months, it’s just a good idea to get the oil changed when you bring it back into service. If you’ve noticed signs of old oil, like a burning smell without overheating, soft knocking noises, and foul exhaust odors, the easiest thing to do is change the oil to see if that remedies the problem.

13. A Tire Wearing on a Wheel Well

A Tire Wearing on a Wheel Well

A tire wearing or rubbing on a wheel well due to an alignment or suspension problem will give off a powerful burned rubber smell. This is usually associated with big plumes of thick whitish, gray opaque smoke from one wheel well when you’re driving.

It usually comes with a grinding or growling noise and strange vibrations as the rubber from the tire digs into the wheel well a few millimeters at a time.

How to Troubleshoot & Fix a Tire Wearing on Wheel Well

If the tire rubbing on the wheel well is due to a suspension system failure, you’ll clearly be able to notice the car riding low on one side, in the front, or in the back. Oftentimes this happens in the rear wheels when a spring or a shackle and hanger fails.

The cost to fix a suspension failure causing a burning smell from the tire wearing on the wheel well can range from $350 to $750.

If the burning smell from the car is due to an alignment issue, the deviation is likely severe enough to cause the tire to rub on the wheel well. Usually, this is from a fender bender or a collision with an obstacle in the road. It’s probably so severe that a simple realignment job won’t fix the problem and the entire front end needs to be replaced.

The cost of a complete front-end replacement ranges from $500 to $2,000.

With the real-world average being around $1,200. Though excessive damage to suspension components can easily drive this cost up.

14. Burned-Out Wheel Bearings

Burned out wheel Bearings

The smell of burning wires with old oil is typically a sign that burned-out wheel bearings that are getting hot. The smell is usually the last little bits of lubricant packed into the housing being smoldered away.

This usually comes with an increasing amount of grinding noise when you accelerate. When the seal fails on a wheel bearing, the precious lubricant inside seeps out. This causes excess heat, which can lead to a burning smell in the car as well as around the compromised wheel well.

How to Troubleshoot & Fix Burned-Out Wheel Bearings

Beyond a burning smell in the car but not overheating, burned-out wheel bearings also produce a humming noise that worsens when you accelerate You might also notice loose steering and even sound like your brakes are grinding.

The cost to have a mechanic replace bad wheel bearings ranges from $250 to $450 per wheel. Though some luxury brands might cost more.

15. A Bad or Clogged Catalytic Converter

A Bad or Clogged Catalytic Converter

A clogged catalytic converter can also create a sulfurous rotten egg odor, that will get worse the longer your run the engine at idle. It might then seem to magically vanish as you drive away. This is usually a sign that fuel contaminants and debris make it into the catalytic converter, as the entire exhaust system runs hot.

It can also cause back pressure in the exhaust manifold, which affects engine performance. This often translates into burning smells that get worse the longer and hotter you run the car. You’ll also notice a sulfurous rotten eggs odor from the exhaust.

How to Troubleshoot & Fix a Clogged Catalytic Converter

Other than a burning smell without overheating a clogged catalytic converter can also show itself in hard starts, poor fuel consumption, black smoke from the exhaust, and sometimes a rattling noise when accelerating.

If you catch it early, you might be able to clear a partially clogged catalytic converter with special catalytic converter cleaner fuel additives.

Frequently Asked Questions

Is It Safe to Drive a Car Making a Burning Smell but Not Overheating?

If you’re stuck on the road and you need to get home or to the mechanic when you have a burning smell coming from your car, you can usually make it a few miles. Though it’s smart to keep the window rolled down in case the smell is caused by an exhaust leak, which could flood the cab with dangerous carbon monoxide.

Some minor causes of a burning smell, like an accidental drip of oil, or a fluid leak from a loose hose won’t readily lead to catastrophic failure. Though more serious faults, like an oil seal leak or burned-out clutch could leave you stuck on the side of the road.

Conclusion

A burning smell from a car but not overheating can have a lot of different causes. Though most of them are not something you should ignore. If you’ve recently had an oil change or you just checked your oil and you know a few drops from the dipstick came off, the burning smell should resolve itself.

If the burning smell from the car has a sulfurous odor, there’s a real risk of it being some exhaust system problem. You need to drive with the window rolled down, and then figure out if it’s a clogged catalytic converter, a muffler leak, or some other problem in the exhaust manifold.

If the burning smell is associated with noises when you accelerate or brake, it could be burned-out wheel bearings, a seized brake caliper, or a tire rubbing on a wheel well. Left too long, these mechanical faults can cause a complete wheel failure leaving you stranded on the side of the road with an expensive repair bill to boot.

Jason Farrell

Written By

Jason Farrell

Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.

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