Burning oil smell in the passenger compartment
The smell of burning oil in the car can be a sign of engine and transmission failure . The most common causes are leaky valve cover gaskets, cylinder-head gaskets or oil seals, and a clogged breather.
This article will help you determine the specific problems that cause the smell of burning oil in the cabin and fix them.
Where can the unpleasant smell of burning oil in the cabin come from
Usually, the smell of burnt oil into the cabin of the car enters through the air ducts of the ventilation system, the entrance to which is located above the engine compartment. It is most noticeable after the engine has warmed up, with the cabin fan running and recirculation mode turned off. The smell can also penetrate through:
The main causes of cabin odor: video
- pedal assembly;
- Center tunnel near the transmission lever actuator;
- Door seals;
- ajar windows.
Persistent smell of burning oil in the cabin clearly indicates a technical malfunction of the engine, rarely transmission and auxiliary equipment. Their sources are usually localized in the engine compartment, so you can feel the smell of burning oil by looking under the hood after the engine is warmed up.
The smell of burning oil in the vehicle cabin can be spread from the exhaust system or under the floor of the cabin elements of the transmission and all-wheel drive system. If you don’t smell it when opening the hood, you should look for the problem on a pit, overpass, or hoistway.
Why does it smell of burning oil in a cabin?
Repeated occurrence of persistent burning smell in the cabin is a sign that the lubricant is getting on the hot walls of the cylinder block, exhaust system and/or adjacent components. It is most often associated with engine problems . The most probable causes of why there may be an odor of oil in the cabin are listed in the table:
| Probable Cause | Signs | The cause of the problem |
|---|---|---|
| Worn oil seals | Oil leakage in the crankshaft area, more often on the timing gear side. | High oil level, increased crankcase pressure. |
| Wear of scraper rings | Oiling of spark plugs, blue smoke and oil smell from exhaust pipe. | Delayed oil changes, engine overheating, natural wear of cylinder heads. |
| Clogged or depressurized breather plug | Oil leaks in the area of the valve cover nozzle or gasket, cracking of the hose. | Breather hose not cleaned regularly, excessive oil mileage. |
| Low oil volume in crankcase | Oil warning light on or low dipstick oil level. | Underfill, leaking, or worn oil in the engine. |
| Leaking valve cover or cylinder-head gasket. | Leaking oil between the cylinder head and cylinder head or between the cylinder head and cylinder block. | Worn or improperly installed gaskets. |
| Exhaust of crankcase gases | Oiling of the nozzle and hose, breather plug, oil filler neck, valve cap. | Clogging of ventilation system, wear of piston rings. |
| Oil leakage through turbine. | Throttle and inlet manifold clogged with oil or blue smoke and oil smell from exhaust pipe, high oil consumption. | Clogged air filter, oil line, oil overflow, turbine malfunction. |
| Transmission problem | Leakage through the gearbox primary shaft packing, deterioration of clutch operation, leaks at the joint between the gearbox housing and the engine. | Use of unsuitable oil, wear of seals. |
| Oil leaking onto the power train housing | Traces of oil on the cylinder block, mostly around the oil filler neck, dipstick hole. | Oil spilled during oil change/check, oil filler cap unscrewed, dipstick seal worn. |
As a rule, the smell, which is the result of oil leaks, increases as the engine warms up because the oil starts to burn off. If there is oil in the exhaust system, symptoms occur almost immediately after the engine is started. During rain or snowfall, the temporary odor may be caused by moisture with oil particles or reagents from the road surface on the exhaust pipe.
How to determine the cause of burning oil smell in the vehicle
To determine the cause of the smell of burning oil in the cabin of the car first of all you need to localize its source. In most cases, the smell spreads:
How to determine the cause of the smell of burning oil in the cabin: video
- From the engine compartment;
- from under the bottom of the car;
- from the exhaust pipe.
Preliminarily determine the exact location will help indirect signs. If you smell burning oil when driving with the windows open, the smell appears or increases when you turn on the ventilation system and disappears after a while after turning on the recirculation mode – most likely, it comes from the underhood space. If the odor appears when the windows are open while parked and disappears while driving, it indicates that the source is under the underbody. When oil is released directly through the exhaust system, in addition to the smell, there is also blue smoke coming from the exhaust pipe. A visual inspection will allow you to determine the source reliably.
If maintenance has been recently performed, including oil change, valve adjustment, replacement of oil seals and gaskets of the cylinder head, valve cover, exhaust manifold, you should first inspect the repaired and serviced components for traces of oil.
Underhood Oil Odor
The main causes of under-hood oil odor:
Oil leaking from under the cylinder head cover
- Oil that got on the engine or gearbox when topping up or replacing it.
- Leaking valve cover and cylinder-head gaskets.
- Leaking crankshaft and camshaft seals.
- Clogged or damaged crankcase ventilation system (breather pipe).
More precisely the source of odor is determined by visual inspection of underhood by traces of greasing. To check the condition of the crankshaft and camshaft seals it is necessary to remove the protective cover of timing gear.
It is possible to eliminate the leak from under the valve cover gasket by tightening the cover fasteners without exceeding the allowable torque. If it does not help – the gasket should be replaced. If the cylinder-head gasket is leaking not only oil but also coolant, including their mixing in the cooling system and the cylinder block. This malfunction is indicated by the coolant smell and white smoke from the exhaust, oil stains in the antifreeze and changes in its level in the expansion tank. A punctured gasket must be replaced immediately.
Oil leak from the crankshaft oil seal
If you find oil around the breather hose, remove it, flush the hose and the oil separator, and then inspect it. If the hose is cracked, it must be replaced. A jammed breather valve also needs to be replaced. A large amount of oil coming out of the breather pipe may be a sign of a worn piston rod assembly, a clogged air filter, a clogged oil slinger drain, or an engine oil level increase.
Oil leaks from under the crankshaft and camshaft seals indicate an increased oil level, increased pressure in the cylinder block, for example, due to a clogged crankcase ventilation system, or wear of the seals themselves. If the oil level is normal, the breather valve is not clogged and there are no signs of overpressure (when opening the oil-filler cap there is no smoke, the cap does not fly off when twisting out), the oil seals must be replaced.
After eliminating the causes of the leak, and if the smell of burning oil in the vehicle interior is a result of oil spillage, you must remove all leaks in the engine compartment with a rag and brake cleaner.
Smell of oil on the underside of the car
Oil leaking from the engine to the exhaust
If the smell of burning oil after or during driving penetrates from the underbody, an inspection of the car on a pit or elevator will help.
Oiling of the engine crankcase pan may be the result of a leaky gasket, insufficient tightening of the drain plug or a deformed o-ring. Worn parts must be replaced to correct the cause.
Oil traces at the joint of the engine and gearbox indicate oil leakage through the gearbox primary shaft oil seal or the rear crankshaft oil seal. The exact cause can only be determined by removing the gearbox, but first, pay attention to a number of features from which you can draw a preliminary conclusion.
Indirectly, transmission oil is distinguished from engine oil by the following signs:
Oil leakage at the engine-transmission junction
- Transmission oil has a pungent sulfur odor and is darker in color.
- If you put the oil-stained fingers together and then apart – the film from the transmission oil will break immediately, from the engine oil will not.
- Dissolve a drop of oil in water – the appearance of a thin rainbow film indicates a leak from the transmission.
A strong smell of burning oil after driving a car with an automatic transmission indicates friction linings burning, which, in turn, is a sign of a low level or insufficient pressure of transmission oil, or other problems in the automatic transmission.
The occasional smell of burning oil on the underside may be caused by oil from the road surface getting into the exhaust system. This most often occurs in rainy weather or when there is snow on the road.
In all-wheel drive vehicles, you should additionally check the transfer case and gearbox for leakage. Oil may be leaking from these due to worn seals, which should be replaced.
Smell of burning in the exhaust
Blue smoke from the exhaust pipe is a sign of serious problems
If you smell burning oil when driving or parking, but you don’t find any leaks in the engine compartment or under the bottom, take a closer look at the exhaust.
Smell, grease, and blue smoke from the tailpipe is a sign of serious problems.
The cause may be a heavy wear of the cylinder head, piston ring lodging, worn oil caps, in cars with turbocharger also problems with the turbine. To eliminate the cause, you need a comprehensive diagnosis of the engine.
Car mechanic with 20 years of experience in the repair and maintenance of cars of different brands. Main area of expertise: diagnostics and mechanics.
Causes of oil odor in the car and ways to solve the problem
When the oil level in your car gets too low or the oil gets “old,” you may smell burning oil in one of its many forms while behind the wheel. These smells indicate that your car needs an oil change and that it’s time to schedule an appointment with your mechanic.
How to determine the cause of burning oil smell in the vehicle
First, let’s look at why the smell of oil indicates the need for an oil change. Oil is vital to your car for two main reasons: its cooling properties prevent the engine from overheating, and its lubricating characteristics cover and protect the moving parts of your entire car system so they interact smoothly without harming each other.
As your vehicle’s mileage increases, the once-clean engine oil that passes through your engine over and over again begins to absorb dirt and small particles, causing it to lose its cooling and protective properties. The smell of burning oil in your car indicates the following:
- Your car needs an oil change.
When dirty oil can’t cool your engine, you may even smell burnt fuel.
- Your car may have a fuel leak.
If you notice a faint smell of oil, especially when you are outside the car, make sure there are no leaks anywhere.
- Insufficient tightening of the elements or gasket could also be the cause.
Having dirty or very little oil circulating in your engine puts your car at high risk of serious consequences. These include the following:
- Engine overheating.
Without exposure to temperature equalizing fresh oil, your car’s engine can overheat, putting other important parts of the engine at risk and shutting down completely (leaving you stranded).
- Engine stalling.
If you keep neglecting to change your car’s oil and the oil level gets very low, there’s a chance that the metal parts of your engine will get so hot that they can melt and cause it to jam, which can lead to a complete car failure.
How to know when it’s time to change your oil
If your car has an appropriate indicator that tracks the oil’s service life, keep a close eye on it. Modern cars have a smart “oil life” monitor located in the center of the dashboard messages.
IMPORTANT: Know the odors that signal the need for an oil change. Don’t put off an oil change until the last minute! If you know you have a long trip ahead of you, evaluate the oil level and condition before you go. Stick to a regular maintenance schedule to ensure optimal performance and longevity of your vehicle.
Common causes of burning oil odor in the cabin
The smell of oil in your car is a thing no one wants to smell while driving. Not only is it uncomfortable, but it can endanger the person sitting in the car. If you smell oil in your car, stop the car and check where the oil is coming from so you can determine exactly how to fix the problem.
There are several common reasons why burning oil smells in cars. These may include the following systems:
- The clutch if it is worn out and needs to be replaced.
- Your brakes from harsh braking or driving on the brakes.
- Your heater, from system debris or a bad heater motor.
- Actual oil burning in your car.
Below we’ll look at each possible cause of burning oil smell in your car.
Burning smell from the engine compartment
If you notice a burning smell of oil in the interior of your car coming from the heater, it could be due to dust or debris in your overheated vents, causing the smell of burning oil. You may also have a problem with your heating system, including a faulty engine, a faulty heater core, or another problem that could cause antifreeze to leak into the system.
The oil filter, if pressurized and if not properly installed, will gradually loosen with road bumps and can cause oil to spill around the engine. When the oil leaks out, it will fill the car. Other signs in the case of a faulty oil filter may be an oil puddle under the car. This problem must be corrected immediately so that the engine can run properly and consistently.
The oil pan has a plug, and if damaged, oil can leak out. If it leaks into the exhaust system, it will create the smell of burning oil in the car. It will also create a puddle when the car is parked at any point. This situation must be corrected immediately to prevent oil from leaking out of the engine.
If oil leaks too many times, it may be caused by faulty or broken engine pads. Oil sealed engine oil seals or bad connections are also no exception. This situation will gradually lead to your car becoming filled with the smell of burnt oil. These pads are usually scattered all over the engine. Valve pads and oil pads have two increased risks of damage.
Smells like oil after repairs and fluid changes are done
An oil change, if not done correctly, can cause excess oil to drip into the exhaust system or other parts. When the engine warms up, the oil will burn off, creating a pungent burning oil smell in the passenger compartment. If the leak is fixed, the oil will burn off completely and the oil in the car will disappear after a while.
Burning oil odor in the cabin from the gearbox
Burned oil smells can occur more often than you think. If you notice an odor when shifting gears and smell what smells like burning newspaper, it can be a big problem. This happens when the clutch surface burns out due to slippage. This type of wear is usually caused by improper use of the clutch, and it can happen to those who are unfamiliar with manual transmission operation.
Other sources
If you often brake hard or drive a lot with the brakes on, going down steep hills, you can cause a lot of friction in your system, which can lead to smoke from the brakes, causing an unpleasant burning oil smell. This can also happen if you forget to disengage the handbrake before your trip. If it happens occasionally, it won’t be a big problem. If it happens regularly, you may experience a more serious brake failure, such as a jammed caliper piston.
If there is an oil leak somewhere in your system, when it is drawn into the exhaust system or engine, it will burn up. If you notice that your exhaust is getting very hot or dark, or has too much smoke, you may be experiencing this problem. Don’t procrastinate with any of these problems, and get your engine serviced in a timely manner.
