How much coolant is needed for radiator drain-and-refill on a 1st gen LS400?
The owner's manual only lists a total capacity of 11.2 quarts.

 

If you're just drainin the radiator itself, and not the entire block. It usually takes about a half a bottle of coolant, and the rest water.

 

A very good tip I read here was to use & shop vac on output mode to force the coolant mix out of the block.

I had a hose feeding water in thru the radiator as I flushed the system so I knew that I had cycled out the old. But my first attempt at getting a 50/50 mixture back in was not succesfull due to the amount of coolant retained in the engine block.

If you try this just from draining & refilling at the radiator , you will have limited success & dangerous implications

damon.