29-01-2014, 01:42 PM
Looks like the overflow pipe for the radiator header tank - basically vents any excess pressure/coolant downwards rather than all over the engine.
1990 Peugeot 205 GTi 1.9 // 1991 Peugeot 205 GTi 1.9 16v // 1992 Peugeot 205 GTi 1.9 // 1999 Peugeot 306 HDi Estate