A deep, rhythmic knocking noise that changes pace with engine RPM, or an engine that simply stops running and won't restart, are among the most serious symptoms covered anywhere on this site — in every documented case below, this points to a specific, well-known design issue rather than routine wear.
Unlike most of the symptoms covered elsewhere on this site, rod knock and sudden seizure are not things to monitor or plan around — they are the end stage of a failure that's already happened or is actively happening. The specific mechanisms vary (bearing wear from a rod bearing's tight tolerances, manufacturing debris left in oil passages, or ringland cracking under extreme tuning stress), but the outcome is the same: continuing to drive the car risks turning a serious repair into a complete engine replacement.
Each case below became well known for a different reason — one from a manufacturing defect significant enough to trigger a multi-million-vehicle recall, one from the inherent tolerances of a motorsport-derived design, and one from aggressive tuning pushing an engine beyond what its internals were built to handle.
This symptom shows up across several unrelated engines and drivetrains — each has its own root cause and its own full writeup.
If you hear this noise in a car you're currently driving, stop and have it towed rather than driving it any further distance, however short.
If evaluating a used car, this noise is disqualifying on its own — no price adjustment makes continuing to inspect the car worthwhile once this specific symptom is confirmed.
For any of the three engines above, read that engine's own dedicated page before buying, even if the specific car you're looking at shows no symptoms yet — all three have documented, verifiable preventative checks (a recall VIN lookup, an IMS bearing inspection, a tuning history review) that matter more than how the car sounds today.