Manual says flush cooling system with water, but no coolant concentrate?

[Mike_R]

The owners manual says to replace the coolant at 120,000 miles/10 years and the service manual says that replacing the coolant involves flushing the cooling system with water until it runs clear, and to only use FL22 coolant but Mazda doesn't sell FL22 concentrate.

How can you then replace the water used to flush the cooling system with coolant If there's not a concentrate?
Because each drain and fill will only replaces half the water/coolant, it would take 4 gallons of the FL22 just to replace 94% of the water that was used to flush.
I would buy aftermarket coolant concentrate but I don't know that there's a way to verify they offer the same protection as FL22.

 

[wlong01]

I had the coolant replaced in my 2019 yesterday. 52k on odo but wanted it done because of the TSB and problems related to the previous coolant corroding the heater core.
Not sure how they did it but they used one gallon of coolant. Capacity is around 8 qts so the rest must of been distilled water.
Total price was $79.00.

 

[200955]

The owners manual says to replace the coolant at 120,000 miles/10 years and the service manual says that replacing the coolant involves flushing the cooling system with water until it runs clear, and to only use FL22 coolant but Mazda doesn't sell FL22 concentrate.

How can you then replace the water used to flush the cooling system with coolant If there's not a concentrate?
Because each drain and fill will only replaces half the water/coolant, it would take 4 gallons of the FL22 just to replace 94% of the water that was used to flush.
I would buy aftermarket coolant concentrate but I don't know that there's a way to verify they offer the same protection as FL22.

If the radiator cap has FL22 on it that's what you should use, otherwise feel free to use an OAT type coolant. Start the car and turn the heater on "high" and wait 30 seconds. This allows the heater core to to drain as it's valve is wide open. Drain the system at the rad with the cap on the radiator removed. Detach and drain the overflow bottle. Yes you probably need two premixed bottles (possibly 3) of the right type of coolant. In essence you are doing "drain and fill twice". If you're adamant about flushing with water, you'll likely have to go to a serious amount of work. What you are really trying to accomplish, besides preventing freezing, is reducing the acidity of the coolant. Acid and aluminum parts do'nt play well together nor do some head gaskets. My VOM meter registered .06 volts when checked between the coolant and engine block but my truck had 1.2 volts and needed changing. Thats's acidity at work and by time you flush twice you have indeed removed about 80% of the old coolant. I would be interested in the exact procedure the dealers use because $79 seems like an awfully low price.

 

[wlong01]

II would be interested in the exact procedure the dealers use because $79 seems like an awfully low price.

Invoice just says Coolant Maint., Drain/Fill, checking belts, hoses and water pump.
$29.00 Coolant $50.00 labor.

Sounds like they drained a gallon and put a gallon in. Hopefully it will give some better corrosion protection. That was my objective.

 

[cz5gt]

they open the radiator tap ... wait for whatever quantity gets out (should be more than gallon as that is lower point)and close it. Then refill more start the engine and refill again.
There is also Mazda procedure for getting air out but not sure if they follow it.
The bad dealer just charge you a gallon or two and dont do anything.
A way is to check the Ph of the coolant vefore and after as it was mentioner earlier. Thats also a good way to see if its time to change .. assuming its clear and no particles flowing in it.

 

[Mazdiod2]

I did a drain and fill at about 50k and the coolant was very clean. It has an aluminum block, etc. I don't think I got a full gallon out when I drained it but I did it twice as recommended.

 

[skid00skid0]

I wouldn't put tap water in the block. If you want to go that route, use distilled water. No minerals to deposit in the rad/engine.

I've always just drained and filled my cars. Same as I do with brake fluid and engine oil.

 

[cadcamjim]

The owners manual says to replace the coolant at 120,000 miles/10 years and the service manual says that replacing the coolant involves flushing the cooling system with water until it runs clear, and to only use FL22 coolant but Mazda doesn't sell FL22 concentrate.

How can you then replace the water used to flush the cooling system with coolant If there's not a concentrate?
Because each drain and fill will only replaces half the water/coolant, it would take 4 gallons of the FL22 just to replace 94% of the water that was used to flush.
I would buy aftermarket coolant concentrate but I don't know that there's a way to verify they offer the same protection as FL22.

My 2021 only has 46k miles on her so I shouldn't have to worry about a coolant flush for a while but I've already have been thinking along the same lines as you; how can you flush the system with water when you can't buy FL-22 at full strength to compensate for the water that remains after flushing?

I guess you could just drain the system the best you can by disconnecting every coolant hose and at that point you could maybe flush just the radiator by itself knowing that virtually all the water will drain out of the disconnected bottom hose and/or petcock. But I would be hesitant to flush the block and heater core as who knows how much water will remain in them.

It's hard to fathom what Mazda was thinking when they wrote that procedure, unless at the time of the writing, undiluted FL-22 was available.

 

[Jmaz]

To me, the10 year/120K miles is too long. So at 6 yr/44K I drained 1 gallon, added1 gallon and drove around to mix. Drained out and replaced1 gallon. Exactly 2 gallons used each time including topping off the overflow bottle. Used the Zerex Asian formula premix.
Did the same a few months ago at ~10 yr/71K using same Zerex coolant but instead of driving around I warmed the engine and held at 2500 rpm for 5 minutes to mix. Coolant was very clean both times (44K and 71K).
This last coolant changeout was a convenient time to do in conjunction with new radiator hoses and thermostat that I replaced proactively. There were no issues with hoses or thermostat ,they were still in decent shape, just wanted some new one's for the next 10-1/2 years. There was no gunk or buildup on the inside of the hoses, so that and the clean coolant drained out leaves me with no worries about the cooling system cleanliness.

 

[HyFlyer]

For me, I just couldn't bring myself to spend (waste IMHO) the money on flushing the system with FL22 so I opted to drain/fill 4 times with distilled water (running the engine for 5 minutes 2500rpm between). Then I put in just over a gallon of PEAK Asian green concentrate for a 55/45 % mix. Peak says they guarantee it for 15yrs / 400,000miles if you flush it first so good enough for me.

I felt like my engine would be better served with a flush and fill of PEAK vs a partial drain and fill of FL22. If Mazda still sold a concentrate FL22 for a decent price I would use that.

... Detach and drain the overflow bottle. ...

FYI, if you put your hand over the radiator cap opening while the radiator is draining, it will create a vacuum and suck out reservoir bottle no need to take it off.

 

[200955]

For me, I just couldn't bring myself to spend (waste IMHO) the money on flushing the system with FL22 so I opted to drain/fill 4 times with distilled water (running the engine for 5 minutes 2500rpm between). Then I put in just over a gallon of PEAK Asian green concentrate for a 55/45 % mix. Peak says they guarantee it for 15yrs / 400,000miles if you flush it first so good enough for me.

I felt like my engine would be better served with a flush and fill of PEAK vs a partial drain and fill of FL22. If Mazda still sold a concentrate FL22 for a decent price I would use that.


FYI, if you put your hand over the radiator cap opening while the radiator is draining, it will create a vacuum and suck out reservoir bottle no need to take it off.

So how do you wash it out?

 

[Mike_R]

wanted it done because of the TSB and problems related to the previous coolant corroding the heater core.

I wasn't aware of that TSB. Glad I was already planning on changing it now at 5 years and 90,000 miles.
I knew Mazda changed the coolant ratio to 55/45 but I didn't know, until reading the TSB, that they also increased the anti-corrosion additive in addition to increasing the coolant ratio to 55/45.

TSB attached for other readers.

It's hard to fathom what Mazda was thinking when they wrote that procedure, unless at the time of the writing, undiluted FL-22 was available.

Indeed.
The TSB mentioned above and attached below says to drain and fill twice and then remove and drain and fill the reservoir but that's just to replace the old fluid after a heater block replacement.
I don't know if Mazda would recommend that if the old fluid is at it's 10 year expiration.

For me, I just couldn't bring myself to spend (waste IMHO) the money on flushing the system with FL22 so I opted to drain/fill 4 times with distilled water (running the engine for 5 minutes 2500rpm between). Then I put in just over a gallon of PEAK Asian green concentrate for a 55/45 % mix. Peak says they guarantee it for 15yrs / 400,000miles if you flush it first so good enough for me.

I felt like my engine would be better served with a flush and fill of PEAK vs a partial drain and fill of FL22. If Mazda still sold a concentrate FL22 for a decent price I would use that.

Yeah, I also can't really stomach the idea of flushing with extra amounts of FL22 or just doing one or two drain and fills every service interval.

Flushing with distilled water and doing the 55/45 ratio is what I initially wanted to do but I thought I'd ask about the service manual procedure and read up on the available coolant concentrates before doing it. I really wish Mazda just sold FL22 as a concentrate! It's so wasteful not to.

 

[HyFlyer]

So how do you wash it out?

In my case, there was nothing bad in the reservoir bottle to wash out. Only coolant.