But then by the time it runs clear, surely to get it back to the correct mixture of coolant will mean repeating the above process with coolant/water mix, which will mean it will be very difficult to gauge exactly when the mixture is correct, and will also mean I’ll have to use loads of coolant in order to flush it through again…?
It’s worth changing the stat whilst changing the coolant. Mine started to fail the year after I had a coolant change.
You’ll get a little more coolant out when the stat comes out, not a great deal more though.
Just use Ravenol concentrate and follow the instructions in the link. Yes it takes time but it’s straightforward. The only thing that really takes time is burping the system to purge the air. Get the front of the car up in the air with ramps and burp the system 3 times , again follow the instructions.
Buy three or four 5l tubs of deionised water from Halfords at about £3 each.
Drain plug on the bottom right (looking from the front back).
Drain then fill with the water. Run up to temp so it all gets pumped round and mixed.
Allow to cool and drain.
Repeat maybe three times.
There is (from memory) a total coolant capacity of 7.5l, so add 3.75l of Ravenol concentrate (fl22). Top up with water.
Run up to temp, allow to cool and top up.
Simple. But does take an hour or three to allow for cooling.
Thanks @McTrucky, so are yoh saying that by the time it’s completely running clear with deionised water, the last drain of the radiator and subsequent top up with Ravenol will leave the system at the correct mixture/concentrate?
Pretty much.
As standard it is a 55% mixture.
I measured how much came out on each drain, and knew what the total capacity was from the manual, so could then work out on each drain how much original mix was left in. Can’t remember the numbers, but on the third or fourth drain it was extremely diluted (equivalent of running clear). You will never get it all out, even with a million changes there will still be some of the original left.
So after the last drain, add 3.75l of Ravenol (equivalent to a 50/50 mix if the total capacity is 7.5l (again working from memory, so you should check). Then top up with water, run it up (levels settle) and top up to the mark. Check it after the first run and just top up with water knowing that when full the concentration will be about spot on.
This seemed safer/easier to me than attempting to drain the entire system in one go.
Do use dionised water. Cheap from ECP or Halford’s.
Or buy the correct length stat from Mx5parts. There are two to choose from dependant on engine number, long or short neck. Both the same the only difference, yes the neck length the one Opie sell is the long neck, you then just trim around 30mm off your large dia hose if your original is the shorter version.