Percolation and that strange fan
Percolation is a phenomenon that happens when switching off a hot engine. Specially with big carburettor jets, and with exhaust outlet and air inlet in the same side of the engine, as in GTTs, heat from the exhaust manifold and engine reaches the carburettor. The carburettor base is water cooled/heated, but with a stopped engine, there is no more water flow, and heat vaporizes the fuel that fills the carb if you give it time. That evaporation makes the carburettor and inlet manifold fill with vaporized fuel (percolation), what will lead to problems to start the engine later, for a while.
Fortunately, Renault installed a wonderful -and quiet :-)- antipercolation fan over the right wheel arch. It blows fresh air over the carburettor (and the fuel pressure regulator) when the inlet carburettor base temperature exceeds a limit, to avoid this effect.