Decided to renew the coolant (first time for me) on my 1998 4.0 s/c V8. Handbook says the “initial fill” capacity is 12 litres. Only 4.6 litres came out (and later went back in) on removing the radiator drain plug. Didn’t find the block drain plugs which may account for some - but 50%+? Is it usual to only drain such a small amount via the radiator? Any guidance to finding the block drain plugs?