in any car. Caused by the reduced airflow around the engine. Then shutting the engine off shuts the fan down as well and leads to "heat soak" further increasing the temperature.
If you've ever had a vehicle with a bad fan clutch (not a Z), you would probably not have noticed anything cruising at highway speeds as the fan clutch is essentially useless above 60-80 km/h due to the outside airflow (depending on car and conditions). You find out its bad when stuck in a traffic jam or idling outside a store as the heat just continues to build.
I think these guys are trying to tell you that all this excessive heat made your engine "think" it sensed knock or detonation. Correct me if I'm wrong.
