I have a 2010 Mazda 3 with 88k miles that I purchased used recently. Looked like it had the original FL22 coolant still in it. My dad and I changed the coolant by draining the radiator and flushing the engine block with water. However only 4 L of the total 8 L capacity drained out. We had forgotten to turn the heater on so I assumed the rest of the coolant was still in the heater core. We filled the rest back with Mazda specific FL22 coolant (as instructed in manual). So far engine runs fine and hasn’t showed signs of overheating. Is there anything to be concerned with? Coolant color is a darkish green in comparison with new FL22 coolant which is a lighter green.
It will probably be fine unless the heater core has gotten corroded or gummed up. If there is no issue just drive it and I would expect everything to be fine.
Most likely, what you two did is OK, … and everything will be just fine.
That said, in general terms, … and I mean general, the best one can do is to have a good quality, long life, coolant in cooling system that is 50% concentrate and 50% distilled water - by volume. Mazda coolant is recommended by Mazda, of course, but good quality long life coolant by a major brand formulated for “Asian” vehicle is OK. (I’m assuming here that you used Mazda 50/50 premix!)
Now, a general comment:
It is recommended that one just use a 50/50 premixed coolant to fill a cooling system, … but remember, when one changes coolant - as you did, you use tap water to flush it out clean, first, … than you drain it all out! Problem, however, is that cooling system actually can not be drained completely - as you found out, and so there is a significant amount of tap water in there - trapped! And, now, if you just pour 50/50 mix to the radiator, you will end up diluting that 50/50 premixed coolant to something less than 50% antifreeze. Will that result in significant dilution? It’s tough to tell, … and so, I will just tell you what I do instead to assure a 50/50 concentration:
I find out what is a total capacity of my cooling system, … than I divide that by 2. Next I pour that 1/2 of volume of full concentrate into the radiator, … than I top up the rest with distilled water. Mission accomplished, … sort of. Than, I warm up the car, … check level, … top up expansion tank with distilled/concentrate if needed. Done, … car overheat, corrosion protected, … coolant freezing protected down to ~ -35 deg. C.
F.S.
Postscript:
… I just checked to be sure:
MAZDA EXTENDED LIFE COOLANT (FL22)
"Premium Pre-diluted Antifreeze and Engine Coolant
(DO NOT ADD WATER)"
… hence your coolant concentration is pretty, pretty low, … I suspect!
F.S.
@figmund-sreud
I will get a coolant tester as per the comment below to see. But we also drained the water out of the radiator after we ran the engine for a little while to flush out the old coolant, so I don’t think any water remained in the system unless I’m incorrect. But thanks for the help guys!
Fair enough. I don’t own a Mazda3, … but, just from an experience, my Miata’s cooling system capacity is 6 litres - per factory spec, but draining it, drains only 4.6 litres. Rest stays in the system - factory service manual says so, and a bucket I drain it into confirms this. Hence a logic of my previous comment. Nothing more, …
Anyway, … checking your coolant with hydrometer is an excellent idea. Mazda’s FL22 coolant, if not diluted with extra water, should indicate:
- Freezing Point: -43°C
- Concentration: 55%
- Specific Gravity: 1.095
… or there a-bouts
Best,
F.S.
Grab yourself an antifreeze tester from the auto parts store. It should only cost a few bucks. Just make sure the solution has the right concentration.
