Hi. I flushed my 1986 Mustang 5.0 thoroughly with distilled water. I brought it to a drive through oil change business where the used the machine to replace the fluid with 50/50 coolant mix. It only tests to -30*C(-22F). I’m in Canada where it gets to up to -40*C and I store the car outside inside a trailer. I need to mix in 100% coolant throughout the cooling system to bring the freeze point closer to -40*C and ensure there is an even freeze point throughout the system. I believe the machine cannot remove everything , water is left in the system, diluting the 50/50 mixture.
If I drain the radiator by 50%, top it up with 100% coolant, run the engine until the thermostat opens and let it circulate. Repeat this until I get -40 freeze point. The radiator is a Mishimoto larger size I believe at 8 litres and the rest of cooling system is about 10 Litres.
Would this be the best way to mix in more 100%antifreeze to lower the freeze point and ensure it’s a consistent freeze point throughout the system?
thanks very much, Long time Scotty fan.
Gareth Cummins in Calgary, Alberta, Canada
At -40 degrees Celsius is the same as real Fahrenheit temperature.
You do have a bit less than a 50/50 mixture by volume since that would protect to -28.9F and you're well short of that, with about 47% antifreeze.
https://www.engineersedge.com/heat_transfer/anti_freeze_freezing_boil_temperatures_15722.htm
To reach -40 degrees protection you need a mixture with about 52% antifreeze. Your procedure sounds basically OK but you want to be careful not to exceed 60% antifreeze. Higher concentrations than that can lead to overheating problems since glycol has lower heat capacity than water.
Would this be the best way to mix in more 100%antifreeze to lower the freeze point and ensure it’s a consistent freeze point throughout the system?
that's what I would do, and it's what you should have done after doing the water flush. Just drain the radiator and fill with concentrate. You don't need to go to those shoddy oil change places.
I cannot be 100% sure that the mixture is even throughout the block
after a few drives, it will be mixed enough.
Ok. Thank you very much. I will report back on how it goes
I added 5 litres of 100% antifreeze to the radiator. Drove it twice to operating temperature to hopefully mix it in well. I tested it each time was about -45*C. I would assume that without using a coolant flush machine I cannot be 100% sure that the mixture is even throughout the block. Probably being over cautious but better than a cracked block.
After the winter I will maybe drain a little out and add some distilled water to reduce the antifreeze concentration a little bit.
At -45C degrees freezing protection you're under the 60% rule of thumb for maximum antifreeze concentration so you should be OK.