I don't want to buy any more coolant !!

Which way does the external thermostat face? Which end connects to the water pump? Sorry to be asking what is probably a simple question but I could REALLY use the help.

1978 124 Spider

don't feel like a fool... i recall having the same dilemma the first time i changed mine. pulled the part and forgot to note which way it went back together. of course... i was interrupted in the mean time

maybe this will help:

Good news/Bad news I guess, that's how I had it ... after removing it I tested it with some hot water and it opens fine. For some reason I cannot get it to work when installed. Hot top hose, hot hose to pump and top half of thermostat is hot (very), but hose to bottom of radiator is cold and fan never engages.

what you have is an air bubble trapped in the head. very common problem. two suggestions for resolution.

you see, the radiator is not the highest point in the cooling system, and getting all that air out is a PAIN:bang: check out this long drawn out technically correct procedure:
http://webpages.charter.net/mbouse/Bleed Your Spider Cooling System.pdf

yeash.. PITA

or my other suggestion is to simply make the highest point in the cooling system accessible as the final filling point of the system.
1. buy a Prestone coolant flush system and install the T-fitting in the center of the heater core hose.
2. fill the system from the radiator as normal. cap the radiator.
3. open the heater control valve.
4. finish filling the system from the newly installed T-fitting. have patience as it takes a little time for all those little air bubbles to find their way to the top.
5. take a long, enjoyable test drive