How to drain the coolant completely.

I changed the coolant today but after removing the lower rad hose and undoing the bleed bolt on the rad I only needed about 6 litres to refill, book says 11-12 litres, what is going on? cheers, John.

Hi Andy, yes, header tank empty; I had it nose down in the driveway and thought I'd pretty-much emptied it, maybe it's worth just doing a drain-down like last time and another 6 litres; this must be close to changing the lot.

The remaining 5-6 litres you're looking for will be in the heater matrix & engine block.

The complete removal of all coolant to create an empty situation is not actually as critical as you think, unless that is you're going down the Evans waterless coolant route.

Rather than trying to remove everything you are much better off draining what you can and doing a flush with a garden hose, the hose will create quite a bit more flow than the water pump ever could which really helps clean things out.

When flushing do so in the reverse direction to normal flow, this reverse flush helps to dislodge and remove more silt than if you just went in the same direction as the water pump stirs water around the system.

Spend some time with the hose method, alternate the flow direction a few times and attach the hose to different points (heater hoses, top rad hose flow into rad, top rad hose flow into engine ect). It can also help to remove the thermostat as it's just an obstruction during the flush process and dislodged silt can get trapped behind it.

Take your time, a really thorough flush process will ensure you remove all the old coolant and more importantly any silt deposits that have collected in the heater matrix, block and rad.

You'll still end up with 5 litres in the block & heater but with a flush it'll be fresh clean water, you can then add 5 litres of new antifreeze to create your 50/50 mix.

It's perfectly possible to bleed & fill at idle but you'll never get that last litre in the system like this.

When completing the bleed process hold the engine at 2-2.5k RPM, observe the coolant level drop in the swirl pot as you increase the revs and the water pump starts to drag the coolant around the system.

When you increase the revs and the level drops fill the swirl pot with the last litre, now let the revs drop back to idle and you'll see the engine will immediately puke out that last litre you just added

So the final process is:

1. Hold the engine at 2-2.5k RPM

2. Observe the level drop in the swirl pot

3. Top off with the last litre while keeping the revs up

4. Quickly screw the brass plug in the swirl pot to seal the system before finally letting the engine return to idle

A 1 litre funnel in the swirl pot helps with this process, as does an assistant to hold the revs up, but it is perfectly doable on your own.

The 2-2.5k RPM on final topping off method ensures that last litre stays in the system where it belongs. You'll end up with a solid column of coolant and consequently better cooling performance in the summer and a far more effective heater in the winter than if you just did the whole process at idle as most do.

Thanks for all the advice from Dave, Dave and Dave. [Is this a coincidence and probably worth buying a lottery ticket?] Hope things work out in Germany Dave, call me when you get back, cheers, John.