Canoe;c-137926 wroteToomanyVolvos;119642 wroteI use the principal that a drain from the radiator only gets half the fluid out.
Method 1: Draining and refilling with known same type of fluid.
Just drain what you can and refill with correctly mixed coolant (50/50), usually about half of system capacity.
Method 2: Changing type altogether or removing unknown coolant type.
You need a few drain and fills to remove the old stuff (with the heater on and run engine until thermostat opens. I try to only add hot water to a hot engine when flushing).... perhaps the first couple with free/mains water (unless your in an area with high mineral tap water, Adelaide?) and last few drain and fills should be de-mineralised water to minimise contamination. I've found generally using this method the last drain will get about half of the de-mineralised water out (about 4L of an 8 L system) and you can add straight concentrate to end up with 50/50 in your system.
Oppolock;c-137901 wroteI use this now, Red block/White block it doesnt matter.
But you MUST flush and flush well before you change over or you contaminate the new coolant.
740/S90/V40t/850 all good BUT flush with the appropriate flushing agent first.
https://www.nulon.com.au/products/cooling-systems/one-coolant
My problem is, that i neglected my coolant system for a while. I put a nulon "flush" into it, and its partially blocked the radiator, and it runs a lot hotter than before the flush. I was thinking of doing a citric acid flush, to see if it would get rid of the crud.
Any thoughts?
Considering the powdered Citric flush Ive come across in the past was blocking the steel coolant pipes around the back of whiteblocks id make sure you use a liquid flush agent.
I use the Pro flush agent from Supercheap but be aware that the thermostats on Whiteblocks can mess with the distribution so I remove them for flushing.
Its also worth noting that you flush any coolant/Heater core BACKWARDS so you blow the crud OUT of the core instead of back through the core.
The other general wisdom to take note of regarding cars that have been neglected coolant wise is that adding some coolants to water or diluted coolant mixes may soften rubber hoses and gaskets including head gaskets.
When i ran my shop Id often ask head issue clients about what the service history was on the car and more than a few times there was nice fresh coolant in the systems.
So be aware.
