Reservoir tank
 

i have a 1984 300 sd turbo diesel.I just orderded a tank from you and it arrived today.There is an extra whole for some kind of connection which isnt on mine and its smaller overall.What connects there and why such a diffent type?Also the car wont start now unless you spray starter fluid in it.What would be the cause of thast?

plug
 

the hole is for the coolant level sensor, the early models like yours did not have it, in your case you need to order a kit to plug it. the part number for the kit is 126-500-15-49.