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2016~2020 Plugged heater core - TSB - 07-007/19

Hi everyone,

just found this TSB not too long ago and thought it was interesting.


Long story short, there seems to be a risk that the heater core gets plugged by debris which would result in poor cabin heater performance. The interesting bits are:
- 2 x production changes where made by Mazda to the Cx-9 try to prevent the problem. (1)They increased the concentration of the coolant to so that the amount of anti-rust additive is higher and (2) then later the composition of the coolant has been changed (the ration of anti-rust additive has been increased). The way I interpret the TSB is that CX-9 built after Sep 1, 2017 have change (1) implemented, CX-9 built after 1 April 2019 have change (1) and (2) implemented.
- the task of replacing the heater core in a CX-9 is a whopping 7.4 hrs of labor!
- If they have a TSB out on this, this means that consumer have already experienced heater core issues. It seems like the TSB initially started with the 2014 mazda 3 and mazda 6 and the previous TSB was issued in 2017. So my rough estimate is that it looks like the issue could present itself in as early as 3-4 years (2014 mazda 3 bought late 2013 to a TSB repair in 2017).
- These repairs are eligible under warranty type A. I have not figured out if this was the 3 years warranty or the 5 year powertrain warranty.

I have a 2018 CX-9 built after 1 Sept 2017, I want to keep it for close to 10 years, I need a good heater core because I live in Canada and I fully believe in preventive maintenance whenever possible. So I figured I might ask my dealer or pay him to change the coolant to the new coolant with higher anti-rust additive concentration, but the thing is I can't find the new specification of the coolant, other than it is FL-22. Which is the same specification than before the additive addition. So I don't really have any way of knowing if the dealer even have the new coolant that was introduced as a change after 1 April 2019, and C-19 doesn't make it easy to chat with them about this at the moment. I certainly don't want to change the coolant for nothing.

Not really a question, but wanted to inform members of the forum and will welcome any comments or ideas on the subject.
 
Thanks! But how do we know if this contains the added additives the tsb mentions. Both pre 2019 vehicles and post 2019 vehicles calls for FL-22.
 
:
2017 Mazda 6 Sport
Thanks! But how do we know if this contains the added additives the tsb mentions. Both pre 2019 vehicles and post 2019 vehicles calls for FL-22.
on page 10 of the TSB it lists the part # of the correct coolant to use
 
:
Mazda CX-9 Grand Touring 2016
I think that regular drains & refills with the proper coolant will keep the anti corrosion and other additives in good strength and keep your system clean. You, or any shop, can drain the radiator and refill with the #0000-77-508E-20 FL-22 coolant. It is pre-diluted, so just drain & refill. There will be no compatibility issues. The clean system is the key. Keep the coolant fresh.
 
I think that regular drains & refills with the proper coolant will keep the anti corrosion and other additives in good strength and keep your system clean. You, or any shop, can drain the radiator and refill with the #0000-77-508E-20 FL-22 coolant. It is pre-diluted, so just drain & refill. There will be no compatibility issues. The clean system is the key. Keep the coolant fresh.
That's probably right. Where there is a disconnect is that this is a long life refrigerant and that the mazda recommend change interval is: "Replace at first 192,000 km (120,000 miles) or 10 years".

But then the heater core apparently is at risk of plugging a lot earlier than that, and almost no one will change their coolant more regularly than the recommended maintenance schedule. But I think you are right, in my case to alleviate my concern the solution may just get into a habit of adding a coolant change to my personal preventive maintenance schedule on more regular basis.
 
:
2017 Mazda 6 Sport
This is a pretty involved repair if it happens out of warranty (a 7 hr job on a CX9). It might not hurt to change out the coolant with the new version as preventative maintenance
 
My thoughts exactly. Seems ridiculous that changing the coolant wasn’t added to the preventive maintenance task, or that a differently designed heater core wasn’t used. A 7 hour job would hit my budget hard, and thats just in labour.
 
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