Hello


My 1987 300E does not have a bleed screw in the top of the thermostat housing. To bleed the cooling system there is a bolt on the top of the head.


I understand that the housing was updated with threaded hole and bolt / crush washer..


I am not sure which point is higher, the bolt in the head or the screw in top of the thermostat housing?




Why and when was the screw added to the thermostat housing?


I will soon be replacing my thermostat and was wondering if I should change the housing to the updated part while I am at it?