Every complaint describes a symptom. A noise, a smell, a feeling through the pedal. We sorted a million of them by what the owner described, then looked at what happened next.
The symptoms do not behave alike. Sorted by outcome they split into two groups with almost no overlap.
| What the owner described | Complaints | Ended in fire | Ended in a crash |
|---|---|---|---|
| Smoke | 6,052 | 44.4% | 1.8% |
| Burning smell | 4,039 | 29.9% | 1.6% |
| Knocking | 8,558 | 1.8% | 2.4% |
| Loss of power | 21,759 | 1.8% | 1.9% |
| Squealing | 2,451 | 0.7% | 3.6% |
| Brake pedal to the floor | 3,350 | 0.7% | 18.3% |
| Grinding | 9,880 | 0.6% | 2.6% |
| Vibration | 18,920 | 0.5% | 2.2% |
| Steering went heavy | 2,847 | 0.5% | 3.5% |
Baselines for comparison: across all complaints, 2.4% involve a fire and 5.8% involve a crash.
The nose is the only sense that predicts fire
Smoke and a burning smell sit at 44.4% and 29.9% — eighteen and twelve times the baseline. Nothing else on the list comes close, and everything you can hear or feel sits below the baseline.
That makes sense mechanically. Grinding, knocking and vibration are wear symptoms: metal contacting metal, a bearing failing, something out of balance. They mean a component is dying, and a dying component is usually just expensive.
A smell means something is already hot enough to break down — insulation, oil on a manifold, a seized brake, a slipping belt. The chemistry has started, and the difference between a smell and a fire is a matter of degrees rather than of kind.
Of the burning-smell complaints, the largest group by component is the electrical system at 1,219 records — and 44% of those involved fire. Wiring is where a smell most reliably becomes flame.
The brake pedal is the other extreme
A pedal going to the floor is almost never a fire — 0.7%. It is the highest crash risk of any symptom on the list at 18.3%, three times the baseline.
Two things make it worse than the numbers alone suggest. It arrives with no warning stage: unlike a grinding noise that builds over weeks, hydraulic failure is discovered at the moment you need to stop. And it removes the ability to avoid the consequence rather than merely causing one.
The pattern matches what we found on brake line corrosion — a rusted line holds until it does not, and the first symptom is the pedal travelling further than it should.
Why the harmless-sounding symptoms are reported so much more
Vibration produces 18,920 complaints and loss of power 21,759, against 4,039 for a burning smell.
That is a reporting artefact, not a frequency one. A vibration is something you live with for months and eventually report out of frustration. A burning smell is something you deal with immediately — and if it becomes a fire, the complaint is about a fire rather than about a smell.
So the smell category is undercounted at both ends, which means 29.9% is a floor rather than a ceiling.
What to do with each group
The mechanical symptoms — grinding, knocking, vibration, squealing — mean book a diagnosis. They are rarely urgent and frequently expensive: our extraction of reported repair costs puts engine work at a median of $3,700 and transmission at $2,500.
The olfactory ones mean stop. Not at the next exit, not at the garage twenty minutes away. Nearly a third of these complaints ended in fire, and the average vehicle it happened to was 6.3 years old.
And the pedal one means do not drive the car at all, because the failure has already happened and the next application is the test.
If the fault is one the manufacturer already knows about, the repair costs nothing — a free VIN check lists the open campaigns for that specific vehicle.
Frequently asked questions
What does a burning smell in a car mean?
It is the strongest fire warning there is. Across complaints describing a burning smell, 29.9% involved a fire against a 2.4% baseline across all complaints — twelve times the rate. Where the owner described actual smoke, 44.4% involved a fire.
Which car symptoms are least likely to end in fire?
Vibration at 0.5%, grinding at 0.6% and squealing at 0.7% — all below the 2.4% baseline. These are mechanical wear symptoms: they signal something failing, but not something igniting.
What symptom most often precedes a crash?
A brake pedal going to the floor, at 18.3% — three times the 5.8% baseline and higher than any other described symptom. It removes the ability to stop with no warning stage, and unlike a fire risk it gives the driver nothing to smell first.
Should I keep driving if I smell burning?
No. This is the one symptom where the data supports stopping immediately rather than continuing to a garage. Nearly a third of these complaints ended in fire, and the average vehicle it happened to was 6.3 years old — not an old car.
Denis Kataev is a serial solopreneur and the founder of ForCar. With 15+ years in software engineering and 10 years in SEO, he builds data-driven products end to end — backed by a sharp eye for design. At ForCar he mines proprietary vehicle datasets, turning raw numbers into buying advice you can actually trust.
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