Burning smell from under the hood

I detected a burning smell coming from my car. I smell it when I open the hood after I've run the car. There is no smoke coming out of the car and I didn't have the AC, heat, or any other devices on.
Experienced mechanics share their insights in answering this question :
Hello. A lot goes on under the hood and many of the components can reach high temperatures. Any fluid leaks coming into contact with these hot components can burn the fluids and cause an odor. An example would be a failed valve cover seal leaking oil all over the engine’s exhaust manifold and burning the oil. Have a mechanic, such as our YourMechanic experts, take a look around under the hood to pinpoint the cause of the burning smell.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

A burning rubber smell

If your car smells like burning rubber, turn off the engine and check under the hood to see if anything looks out of place. Chances are that the smell results from a belt or other part slipping and rubbing against the hot engine. If you can`t identify the problem, take your car to a mechanic.

Burning rubber smells can be from slipping car belts, broken tensioners, and more. We`ll give you expert advice on that. It`s common to notice a burnt rubber smell coming from your car. Often, it is not tire-related; the odor might come from rubber contact with a hot engine or exhaust pipe instead.
If your engine smells of burning or smoke, there are two possible reasons for this: it`s overheating or there`s a problem with the oil. Generally if it`s overheating, you`ll know about it because a warning light should appear on the dashboard.
5 Common areas that can cause a burning smell from your car: 1) the clutch – may result from riding the clutch or needing a replacement, 2) the brakes – can occur from heavy break usage or riding the brakes, 3) an electrical short, 4) the heater – may result from debris in the system or from a bad motor, or 5) burning …
Why Does My Car Smell Like It`s Overheating, But It`s Not? When you get a burning smell, even when your car isn`t overheating, it could mean you have a coolant leak. The leak could occur from a loose or faulty coolant reservoir cap or a more serious fault. You could also get a burning smell from a defective heater.
Reason #3: Bad Catalytic Converter

It can stop breaking down the sulfur made during combustion. As a result, excess sulfur in the exhaust gas can often be detected in the cabin as sulfur has a distinct rotten egg odor.

Common reasons for this to happen: Exhaust Leak: If the exhaust smell is inside the vehicle cabin, a leak in the exhaust system is almost always the cause. A leak can develop anywhere in the exhaust system and this can result in a heavy exhaust smell in the vehicle.
If you are noticing a funky, burnt rubber smell as you are driving, there is a good indication that there is something wrong with the manual transmission system. Some possible transmission problems that you could be experiencing include: Slipping pressure plate. Burnt clutch.
A pretty common issue that occurs with engines that are running low on oil is a strong burning oil smell. If you`re driving and you start to smell an oily odor coming from somewhere, that`s usually a pretty good sign your vehicle is due for an oil change.
White vinegar cuts through odors naturally. Try wiping down furniture, washable walls, floors, etc. with white vinegar. Also, try placing several bowls of vinegar around the room with the smoke damage, leaving them there for several days.
That being said, an electrical fire can smell like the following: Burning Plastic: The acrid odor of an electrical fire is often described as that of burning plastic. This is because wiring insulation, connectors, and many other electrical components are made of plastic materials.
A Bad Catalytic Converter Can Burn Through Overtime

If you have to deal with a fully plugged catalytic, avoid driving your car. If you notice smog coming from your car, it is best to seek professional help immediately.

Most catalytic converter failures fall under one of three categories: Overheated, melted or broken converters.
Driving with A Failed Catalytic Converter

If you`re noticing slow powertrain performance, reduced acceleration, a smell of rotten eggs or sulfur from the exhaust, dark exhaust smoke, or extreme heat from under the vehicle, these are symptoms of a clogged Catalytic Converter, and it should be replaced quickly.

Our sense of smell is the strongest of the five senses, and the one most tied to memory and emotion. 75% of all emotions generated every day are due to smell. Scent affects mood, concentration, memory recall, and emotion. Research shows there is a 40% improvement in mood after being exposed to pleasant scents.
A car with a musty odor may mean that there`s moisture buildup inside your car, and it could be due to a clogged air filter, a leaking trunk, or a vehicle with a leaded engine. You may try to fix any moisture buildup inside your car by checking for a clogged air filter or leakage.
A rotten egg smell in your car often indicates a malfunctioning part in the fuel system. If the catalytic converter, fuel filters, or fuel pressure sensors are worn out or damaged, a sulfur gas can leak out and make its way into your car`s cabin.
If it is dark, dirty or milky (or has a distinct burnt smell), then that`s a pretty clear sign that you are overdue for an oil change. If you are driving and can physically smell burning oil, then that`s usually a good indicator that it`s time for an oil change.
Blue smoke from the exhaust: Bluish smoke can indicate your car is burning oil during the combustion cycle. Burning oil smell: A thick burning oil smell could mean oil is seeping onto hot engine parts. Frequent low oil light warnings: Regular low oil warnings can indicate excessive oil consumption or a car burning oil.
Identifying a Coolant Leak

One way to tell is by looking at the color of the smoke coming from the vehicle`s exhaust pipe. If the smoke is white, it`s probably just water vapor and not coolant. But if the smoke is blue or black, that`s a good indication that your car is burning coolant.

Burning Smell

If you notice the odor of burning plastic, smoke, or melting wires, this could indicate that your transmission is overheating or that the transmission fluid is burning. Worst case scenario, this smell could lead to an electrical fire, which is incredibly dangerous for you and other drivers on the road.

Some common signs of a leaking head gasket include: Coolant puddles under your vehicle. Low coolant level in your reservoir. A strong, acrid smell when your engine is hot – some describe this as a “sweet” smell coming in through the car vents.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

I’ve been told I have leaking valves. Burning rubber smell, no external leaks but dripping noises, car not overheating
ANSWER : Hi there. It sounds like the valve cover gaskets are what is leaking. The gasket is made of rubber and can become hard and brittle over time and start leaking oil. The leak may not be one where it is literally leaving a puddle, but more along the lines of seeping out. The rear valve cover tilts toward the cab of the vehicle and when it leaks oil, this oil makes its way onto the very hot exhaust manifold. Both valve covers can leak enough oil at the corners toward the transmission to run down the engine block and end on the hot exhaust center pipe under the oil pan. Both of these pipes will literally burn the oil and produce the smell and sometimes smoke or what looks like steam. The condition will not go away on its own and will only get worse with time and use. I suggest having a qualified technician perform an inspection to confirm the leaks and avoid replacing unnecessary parts. Your Mechanic has several technicians available that can assist you with an oil leak inspection.

Just found out that my vehicle has been leaking oil for at least 2 yrs. Would smelling that burning oil smell cause health issues?
ANSWER : Hi Larry. As the co-founder or a non-profit that focuses on education, awareness and screening for respiratory diseases targeting the automotive community, I am happy to answer a few questions for you to clear up some facts. First, there are multiple materials, chemicals, and substances on a vehicle that are emitted from the mechanical actions of the vehicle that MIGHT reduce respiratory function and lead to a diagnosis of COPD (Chronic Obstructive Pulmonary Disease) or other respiratory diseases. However, it is nearly impossible to prove the precise source that can cause respiratory problems. Whether due to excessive exposure to these substances, social choices (smoking), workplace environment, indoor air quality in the home, even certain genetic conditions, it is possible for lung function to decrease over time. At Right2Breathe.org, we always recommend that anyone that is experiencing any breathing issues, visits their primary care physician and have them complete a spirometry exam (a non-evasive breathing test). This will allow them to measure your lung’s function and begin the official diagnosis process. Thank you very much for asking this important question. Feel free to contact us if you have further questions.

Plastic burn smell when opening driver door. Cannot smell inside cabin. Oil full, brakes ok.
ANSWER : Hi there. It is very difficult to "guess" as to the cause of a smell like you’ve described without being their to inspection the car personally. I would highly recommend having a professional mechanic complete a smell in the car inspection; especially if you believe it to be an electrical short.

hood latch locked before could. Lose hood and now hood is jammed and can’t get it unjammed
ANSWER : Hi there:

If the hood was having a problem closing and won’t open now, it’s typically an indicator that the hood latch itself is damaged or simply needs to be lubricated. The best way to have this issue repaired or diagnosed is to contact a professional mechanic and have them complete a door will not open inspection. This will allow them to determine why the front hood on your 96 Ford Explorer is locked and recommend the right repairs.

Car shut off while driving, smoking (or steam) from right side under hood, strong burn smell, check engine light on until next day
ANSWER : Hi there:

It’s very difficult to diagnose exactly what type of damage may have been done to your 2003 Honda Civic during the overheating issue without physically inspecting this onsite. It is possible that the head gasket may be damaged, which might be why you add coolant but don’t see a leak. If this has occurred, you most likely have suffered serious engine damage. To know for sure, you should have a professional mobile mechanic complete a car is smoking from engine or exhaust inspection; so they can trace what might be wrong with your car and recommend the right repairs.

I have a strong burnt metal smell.
ANSWER : Most of the time, bad smells indicate leaks. Oil, coolant, or brake fluid can leak onto hot surfaces and cause some really potent eye burning type smells. But in your case, I’m suspicious of the brakes. If you have a brake caliper that is sticking, it can cause the car to pull in the direction of the bad caliper. It will also cause the brake lining to overheat and produce a really acrid smell as the binders in the lining burn off. You can check for this if you have a non-contact thermometer. Drive the car for a while and then check the temperature of the front wheels. One of them might be hot. If you want some help with this, you can Contact Your Mechanic. They can send a technician to your home or office to check out your bad smell and tell you what it means and what can be done about it.

I smell oil burn smell in car. This started after my last oil change. What could it be?
ANSWER : Depending on how long ago your last oil change was, this may be the result of an oil leak or potentially oil that has dripped on the motor somewhere that has been heated up. This happens occasionally when changing oil and is usually not a cause for concern, however if there is any indication of an oil leak (even a slow or slight leak), this will need to be looked at by a qualified mechanic such as one from YourMechanic as this will only continue to get worse.

Soap smell coming out of car after cabin change. Changed filter the the smell is still coming. What to do about this strong smell?
ANSWER : Hi There,
As you know, your car has a cabin filter that serves to filter the air that is introduced to the cabin inside the vehicle. The best way to remove your cars interior ac odor is to use a cleaner that uses enzymes. Enzymes in cleaners kill odors at the source and completely kill the smelly substance material and therefore stopping the a bad smell. To get rid of the smell, try the following: First turn on the ac to full, make sure the “recirculate” button is not on, spray a large amount of cleaner with odor killing enzymes into the EXTERIOR air intakes that are located just below the windshield wipers, let the car run for about 10 minutes with the ac on, after 10 minutes turn off ac and spray the cleaner into the ac vents on the INSIDE of your car. After doing all this, let the car sit for 20 minutes turned off and windows rolled up. Then repeat if the smell is still in the car. By doing this you are killing the bacteria or mold in the car ac vent ducts and also the evaporator mold that may be present.