GGR thanks for that info I have just bought an autobooks workshop manual off ebay (simular to haynes) for the 250 series car which icludes the 250SE so that should have coolant quantities in it, hopefully it will also help me with the rebuild.
I have a mercedes shop manual which came with the car which is a big thick book and is for passenger cars from 1959 but I struggle to find specfic information on the 1966 250SE coupe for the body and electrics and the 1970's 280SE for the engine and transmission.

I am presently trying to make sense of all the metal and rubber pipework once I have that sorted I will start on the engine electrics so there possibly be more posts on that subject.

I cant believe how mechanically complex this car is for a vehicle manufactured over 40 years ago

I am thankful for all the advice given