My Project nad to td 405

[Doseph]

Sounds like your thermostat gasket.
i ahev this problem too, I got a new thermostat from eurocarparts but it didnt seal properly so i would say call up Peugeot and get a new thermostat from them which should come with gasket
should be part no 1338 23 i think, im sure someone more knowledgeable can confirm