Audi A4: Burning Smell → Causes + Diagnosis
One of the most troublesome problems that you can experience in a vehicle is a burning smell. If your Audi A4 has a burning smell, there are a few different reasons that this can happen. Typically, the smell is caused by some type of fluid (oil, trans fluid, etc..) hitting the exhaust or other hot parts of the engine.
Burning Smell Causes: Audi A4
Here are the most common reasons that you may be smelling a burning smell coming from your A4.
If your A4 has brakes that are sticking, they’ll heat up and cause a rather strong smell. It’s often described as a rotten egg smell.
This typically happens when a caliper sticks (disc brakes), or when a wheel cylinder fails (drums). Here’s a more detailed writeup on this subject: Audi A4 Brakes Sticking.
Oil on Exhaust
Another reason you may experience a burning smell coming from your A4 is oil on the exhaust. This is almost always caused by oil leaking from the valve covers onto the exhaust manifold.
If this is the case, take a look under the hood with the engine cold and off, you should be able to see evidence that the oil is leaking. If you find it you’ll either need to replace the valve cover gasket, or re-torque the bolts. They can loosen with the years of vibration.
When this is the case, you should be smelling the burning smell at almost all times, and it should be strongest coming from the engine bay. You’ll notice it more at lower speeds than high speeds.
Another very common reason for a burning smell is burning oil. If your A4 is burning oil, you should be able to smell it the most from the tailpipe. It should also be accompanied by blue smoke, and the oil level should go down as well.
Burning oil is typically caused by a bad PCV system, piston rings, or valve guides. There’s plenty on diagnosing this issue in the article linked above.
It is entirely possible that something in your engine bay is rubbing the serpentine belt. This often happens when one of your engine accessories begins to lock up. You should hear a squeal from the serpentine belt as this is happening. It’ll smell heavily of burnt rubber.
Your Audi A4’s serpentine belt turns the water pump, alternator, power steering pump, and A/C compressor. If one of these starts locking up, the pulley won’t turn and the belt will burn up. It’s usually not a long period of time before the damage is so great that the belt breaks.
Your A4’s air conditioner is powered by a compressor that moves refrigerant through the system. The coolant has more than one function. Beside the obvious, it also lubricates the compressor. If the coolant level gets too low, the compressor will begin to burn up and you’ll have a burning smell.
There are many hoses that run to various portions of your engine. With today’s tight engine compartments, rubber hoses have an exact place that they need to be. They are kept in place by a series of nuts and bolts, pins, and keepers. If they get loose, they could rub the engine or get melted by heat from the exhaust.
The burnt smell that comes from an engine overheating is caused by two things. The first is the coolant itself. The second is all of the oil and fluids on the engine burning that wouldn’t normally burn.
You should check your temperature gauge and make sure the coolant level is ok. Never trust a warning light entirely. The signs of overheating include the bad smell, and if it gets bad enough, white smoke will start to pour out from under the hood.
There is plenty of trash blowing around the highways. Given enough time, your Audi is going to pick something up.
One of the most common things that happens is picking up a shopping bag in your radiator. This will cause the engine to run hot or overheat.
It’s also fairly common for trash to stick to the exhaust, then smolder and burn. Make sure that your A4 is cool before you inspect it for any wayward trash.
If you happen to fry one of your A4’s fuses, or if an electrical circuit is damaged, you may smell a brief burning smell.
Diagnosis: Burnt Smell Audi A4
Here are some practical steps that you can take to help you narrow down where the burning smell is coming from:
- Inspect the exhaust system and radiator for debris. Make sure your A4 is cold before touching anything.
- Is there an oil leak? Look for a pool of oil where you normally park. If the oil is making it to the ground, some of it may be burning on the exhaust.
- How does the serpentine belt look? It should feel grippy and not be cracked or smooth.
- Look at the exhaust. Does it have an overabundance of smoke? Does it look extra blue or white to you?
- How is the oil level? Does it appear that you are consuming oil?
Conclusion: A4 Burning Smell
There are a lot of reasons that your Audi A4 may have a burning smell. With a little observation, and the list above, hopefully you can narrow them down a little bit.
If there is anything that you would like to add, please leave a comment below. Good luck!
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