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Draining old antifreeze from engine block?

I'm replacing the old antifreeze/coolant but without an engine drain plug wasn't sure how to get all the old mix out. According to the book the total cooling capacity is 7ltrs with recommended 50/50 ethylene glycol antifreeze/coolant. I remove the radiator drain plug but only

3.5ltrs comes out so I assume half of the old mix is still left in the engine block.

To get the old stuff out do I drain the radiator and fill it up with plain water and let the engine run to circulate the old mix from the engine block into the radiator and then keep draining & filling up with plain water until I see no more old antifreeze mix entering the expansion tank?

Reply to
John
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Flush the block through with a hose until it no longer runs coloured water. You have a block full of water at that point. Connect all the hoses and bits back up and fill the system with the required amount of *neat* antifreeze - so for a 7 litre system put in 3.5 litre of undiluted glycol. Then top up to full with the small amount of water you will be missing.

Reply to
Chris Street

Easier said than done. You can flush the radiator fairly easily, but flushing the block require that you find the engine bottom plug or remove the water pump or something like that...

Reply to
Johannes

Depends on the car, but one method I use is to identify the heater hoses and back flush with the thermostat off the engine block.Strongly recommend that you check the levels as you may have head gasket problems if not fully topped up (airlock in system)

It is a good idea to flush out a rad of it requires it, but that depends on age of vehicle. I usually go overboard with a newly acquired car as history on this sort of maintenance is not available.

Me, Iwould just top up with required amount of antifreeze (3.5 litres in your case) and as long as you replace fluid out with fluid in, then you have the required protection.

Reply to
Gavin

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