CX-5 heater core issues discussed on another Mazda forum

⋯ Still hope mine never needs changing though. :)
So the problem is the FL-22 coolant from factory, not the heater core itself. Based on the latest TSB posted above, you won’t escape this potential problem unless your CX-5 isn’t in the stated range. Looks like we‘d better flush out our factory FL-22 coolant earlier than scheduled 120,000 miles / 10 years with new formulation OEM FL-22 coolant.

2013-2019 CX-5 vehicles with VINs lower than JM3 KF ****** 605884 (produced before Apr. 1, 2019)

NOTE:
To solve this concern, two mass production changes have been implemented.
a) The concentration of the coolant has been increased so that the amount of the contained anti-rust additive is higher.
b) The composition of the coolant has been changed (the ratio of the anti-rust additive has increased).
SUBJECT VIN RANGE do not have mass production change implemented.
 
If you decide to undertake heater core replacement be prepared to perform a refrigerant recovery and charge system after reinstalling everything.
The write-ups I’ve seen have never mentioned the need to disconnect AC lines during heater core replacement like the Mazda Workshop Manual stated?

Heater Core


Seeing how invasive this swap is I guess I’m glad I’ve done a couple coolant services at this point and didn’t rely on the long life service intervals. Nothing certain though I won’t have a failure of heater core or radiator in the future though.
If your replacement OEM FL-22 coolant is newer than Apr. 1, 2019, you may be fine but the replacement schedule is now 60,000 miles / 5 years.

No wonder Mazda dealers don’t sell FL-22 concentrate coolant anymore about the same time in 2019. And the pre-mixed 55/45 FL-22 coolant is the only thing available.
 
Take a look again at that thread.. many mentions of disconnecting the AC.

My original coolant was drained during the rear main seal repair in 1/2019 and then I replaced mine again in 2/2023.

I definitely will be doing this re-crimp option if the issue ever arises.
 
Take a look again at that thread.. many mentions of disconnecting the AC.

My original coolant was drained during the rear main seal repair in 1/2019 and then I replaced mine again in 2/2023.

I definitely will be doing this re-crimp option if the issue ever arises.
My coolant was changed at the 6+ year mark (summer of 2020 -- used Zerex Asian ). Coolant looked great. Contemplating using FL22 this time.
So the problem is the FL-22 coolant from factory, not the heater core itself. Based on the latest TSB posted above, you won’t escape this potential problem unless your CX-5 isn’t in the stated range. Looks like we‘d better flush out our factory FL-22 coolant earlier than scheduled 120,000 miles / 10 years with new formulation OEM FL-22 coolant.

2013-2019 CX-5 vehicles with VINs lower than JM3 KF ****** 605884 (produced before Apr. 1, 2019)

NOTE:
To solve this concern, two mass production changes have been implemented.
a) The concentration of the coolant has been increased so that the amount of the contained anti-rust additive is higher.
b) The composition of the coolant has been changed (the ratio of the anti-rust additive has increased).
SUBJECT VIN RANGE do not have mass production change implemented.
Thanks for the heads up.
 
Thanks!

Great video find!!! Good to know if I ever run into this issue.

I’d be surprised if FORScan or OBDLink can’t see those temp sensors. I’ll have to check on mine.. never had a reason to query the one by firewall before.

After reading about the 2 coolant temperature sensors and their relation to the heater core, this afternoon I decided to see if my semi- cheap (~$50) code scanner had the option to display both. Well it does, in *F (not voltage) as ECT1(engine temp) and ECT2 (heater core outlet temp). The car was sitting for hours after being used this morning so wasn't totally cold and it was 80* outside. After running a few minutes the ECT1 was 142*F and ECT2 was 139*F. Then , with heat position selected I turned the fan on HI and in less than a minute the ECT2 dropped to 128-129 thus giving the expected temperature drop as heat is removed from the coolant as designed. I then turned the fan OFF and the ECT2 slowly increased to almost match ECT1 again.
Although not rigorous, this simple little test proved a few things to me :
1) as mentioned, the scanner picked up heater core outlet temperature on live data. Nice.
2) ECT1 and ECT2 are almost identical thus indicating good flow and that both sensors are good.
Am posting this in case anybody else is curious enough to check their car.
 
Appreciated.. yes, seen that, agreed..alternative approaches far more economical and reasonable. Unrelated I tried tackling the the well known power seat vibration noise cable under the driver seat. In similar stories seen..take the whole seat apart, etc..phoey.. my hands small enough short of scraping finger on sharp metal, raised the seat all the way up and was able to pull that cable out of the tray. None of the dealerships close by had the cable part in stock. I lubricated that cable sleeve before putting it back together which was a bit more challenging to align back into the drive sockets but snaped back in the mounts and the noise was still there, so I will try that fix again with a new cable to order yet. It's a curious phenomenon that noise and vibration arrives out of that cable. Seat works otherwise fine despite the screeching noise. For the high points that Mazda delivers.. there's a few weak spots here, nothing is perfect.

The dealership however did have the FL22 coolant in stock purchased the gallon. The overflow reservoir just a teaspoon of fluid so I brought that back up the L level. Again mom's car so my cursory visit to tend to this vehicle of hers. The dashboard warning lights are out and I think I erased the stored code with the ODB tool. We took a short local trip and I kept the temp to max 90F setting. The air is warm full fan and I wouldn't necessarily say it was hot to the floor vents but I don't know what to expect is normal high cabin heat delivery for this vehicle, every make is a bit different on that, my Toyota truck runs far hotter for highest heat setting. I replaced the cabin air filter too which was plenty dirty, small debris, in need of replacement. All else fails the seat warmer works.

I asked to be alerted if the code returns. Local Mazda dealer to her is offering a service special for the coolant flush through the next month, so get that scheduled. But warned that may not be long-term remedy to be faced with the heater core replacement short of prescriptive tshoot steps. If it was my car I might be tempted to the diy procedure, but I won't be tackling any flavor of that procedure, can see some of the part exposed with the glove box removed, no leaks, but it's a bit too much for me to get any closer to extract it.
 
So the problem is the FL-22 coolant from factory, not the heater core itself. Based on the latest TSB posted above, you won’t escape this potential problem unless your CX-5 isn’t in the stated range. Looks like we‘d better flush out our factory FL-22 coolant earlier than scheduled 120,000 miles / 10 years with new formulation OEM FL-22 coolant.

2013-2019 CX-5 vehicles with VINs lower than JM3 KF ****** 605884 (produced before Apr. 1, 2019)

NOTE:
To solve this concern, two mass production changes have been implemented.
a) The concentration of the coolant has been increased so that the amount of the contained anti-rust additive is higher.
b) The composition of the coolant has been changed (the ratio of the anti-rust additive has increased).
SUBJECT VIN RANGE do not have mass production change implemented.
Amazing.. I hadn't read into the implication of the TSB as the coolant formulation in and of itself as the culprit. So for the trivial 2 gallons of coolant replacement that could have been done much earlier, owners are faced with $3000 repair of the heater core because of the factory build coolant damage? Wow!! Is there something other than iron and oxygen exposed to the coolant that is producing rust? I ask AI and need iron, oxygen and water for rust but can get it when iron is exposed to chloride without oxygen.

It's a bit infuriating that the first TSB arrive 2 years after the build and the entire span of time that has taken place if there was anyway to get ahead of the impending loss or the conspiracy here is that after 2 years, it didn't matter, the loss of the heater core was already a sealed fate.
 
There is actually an earlier 2016 TSB



IMG_2295.jpeg


I’m just using Zerex Asian in mine.. considering the revelation that the FL22 may have contributed to issue I’m feeling even better about it now.

IMG_2296.jpeg
 
⋯ Unrelated I tried tackling the the well known power seat vibration noise cable under the driver seat. In similar stories seen..take the whole seat apart, etc..phoey.. my hands small enough short of scraping finger on sharp metal, raised the seat all the way up and was able to pull that cable out of the tray. None of the dealerships close by had the cable part in stock. I lubricated that cable sleeve before putting it back together which was a bit more challenging to align back into the drive sockets but snaped back in the mounts and the noise was still there, so I will try that fix again with a new cable to order yet. It's a curious phenomenon that noise and vibration arrives out of that cable. Seat works otherwise fine despite the screeching noise. For the high points that Mazda delivers.. there's a few weak spots here, nothing is perfect.
Mazda dealers can always order the OEM parts for you and they usually arrive within a day. There’re 2 parts (cable / shaft) related to different power seat problems. Mazda OEM part #, TK81-88-0D1, is the long cable which need to get replaced when the seat is making noise during forward / backward movement because it vibrates. The short cable / shaft which isn’t available from Mazda is for the problem when the seat only moves forward / backward on the right side rail because it’s broken.

Power-seat noise

2013 CX-5 Power seat parts

Adjuster Motor…Small Cable Part #?

You can find solid short shaft available to replace the broken original flexible short cable from eBay or Amazon. But some have been complaining the solid short shaft is noisy in addition to lack of breaking-away protection.

Update: I found a perfect flexible short (50 mm) shaft for $9 including shipping from China on AliExpress. It took only 11 days from order to delivery. See photo below.

The solid shaft sold on Amazon for $25 is a ripoff. At Home Depot, you can get 1/8" square key stock 12 inches long for $2 - enough to make 6 shafts.

As I mentioned above, I think the solid shaft is a bad idea. If the seat jams, then the shaft will not break and something more expensive will fail, like the motor or the gear drive.

Hope this is helpful to someone.
View attachment 323667

Hey guys. The short cable/shaft is available on AliExpress.

I've just ordered it, hope it will fit. Ordered 50mm.
 
Last edited:
There is actually an earlier 2016 TSB



View attachment 328543

I’m just using Zerex Asian in mine.. considering the revelation that the FL22 may have contributed to issue I’m feeling even better about it now.

View attachment 328544
This Valvoline Zerex coolant for “Asian vehicles” can’t be used on Toyota’s? ;)

Since Mazda engines don’t have engine block coolant drain plug, they can’t do complete coolant drain easily. I hate to mix old FL-22 coolant with fresh Zerex Asian coolant, where we’ll never know what kind of chemical reaction would happen. Like we don’t want mix any ATF with Mazda ATF FZ when we do the ATF drain & fill.
 
There is actually an earlier 2016 TSB



View attachment 328543

I’m just using Zerex Asian in mine.. considering the revelation that the FL22 may have contributed to issue I’m feeling even better about it now.

View attachment 328544
Restated.. if action was taken as early as 2016 one year after purchase, would that have otherwise prevented what was determined to be the cause attributed to the poor formula of FL-22 at the time? I guess from that post it wasn't yet determined the formula was bad. The VINs span as much as 6 years for the CX-5. Other than TSB post stating up to April 1, 2019 build what day did Mazda actually change the coolant formula on the factory floor? My conspiracy is rather than flush millions of gallons of spoiled coolant or find someway to fix the mix depending on when the discovery occurred, used up what was available otherwise risk production line stopped. Deal with it later.

In mom's case it's more like the customer depends on the dealer to proactively address the TSBs. Had the failure occurred in 2016, I think it would have been a warranty solution.

Part of me wonders if this is just masking a larger design issue with the cooling system and how it is maintained for Mazda. Not that other brands don't have other sorts of issues. At the time this wasn't known. This CX-5 was up against the Subaru Forrester. The Subaru had a lot of news at the time of the high oil consumption, foils and frustrations for customers, and determined some bad run of engines, but that problem showed up pretty quickly after purchase.

Thanks for the label picture of the 4 makes as such compatible with the questionable coolant formula, how much of that is shared among them? I'll take them off the list of future vehicle replacements. There's a reason why Toyota doesn't use this formula? I did get some feedback from a mechanic on what was different with Toyota coolant.
 
This Valvoline Zerex coolant for “Asian vehicles” can’t be used on Toyota’s? ;)

Since Mazda engines don’t have engine block coolant drain plug, they can’t do complete coolant drain easily. I hate to mix old FL-22 coolant with fresh Zerex Asian coolant, where we’ll never know what kind of chemical reaction would happen. Like we don’t want mix any ATF with Mazda ATF FZ when we do the ATF drain & fill.


I plan to do 2-3 year drain and fills at this point.. enough of this long life or lifetime fluid non-sense.

As far as I can tell 3rd party replacement is just less of the additives. The labels basically showed same ingredients with different concentrations. I’ve never seen documented cases that long runs on coolant are a good thing on any vehicle.

Lifetime Toyota WS AT fluid is it’s own debacle in Toyota AT transmission failures. I’m talking relatively 2008+
 
Just for a little background on what I have seen

I’ve been here since the summer of 2014 and this has not been a common problem on the CX-5’s of owners here.

There are lots of conspiracy theories on Toyota coolant as well when they went to the long life pink. I treat is as old school coolant and do drain and fills every 2-3 years.

Restated.. if action was taken as early as 2016 one year after purchase, would that have otherwise prevented what was determined to be the cause attributed to the poor formula of FL-22 at the time? I guess from that post it wasn't yet determined the formula was bad. The VINs span as much as 6 years for the CX-5. Other than TSB post stating up to April 1, 2019 build what day did Mazda actually change the coolant formula on the factory floor? My conspiracy is rather than flush millions of gallons of spoiled coolant or find someway to fix the mix depending on when the discovery occurred, used up what was available otherwise risk production line stopped. Deal with it later.

In mom's case it's more like the customer depends on the dealer to proactively address the TSBs. Had the failure occurred in 2016, I think it would have been a warranty solution.

Part of me wonders if this is just masking a larger design issue with the cooling system and how it is maintained for Mazda. Not that other brands don't have other sorts of issues. At the time this wasn't known. This CX-5 was up against the Subaru Forrester. The Subaru had a lot of news at the time of the high oil consumption, foils and frustrations for customers, and determined some bad run of engines, but that problem showed up pretty quickly after purchase.

Thanks for the label picture of the 4 makes as such compatible with the questionable coolant formula, how much of that is shared among them? I'll take them off the list of future vehicle replacements. There's a reason why Toyota doesn't use this formula? I did get some feedback from a mechanic on what was different with Toyota coolant.
 
Just for a little background on what I have seen

I’ve been here since the summer of 2014 and this has not been a common problem on the CX-5’s of owners here.

There are lots of conspiracy theories on Toyota coolant as well when they went to the long life pink. I treat is as old school coolant and do drain and fills every 2-3 years.
Fair. But I have a sense of reaction from call to a dealership this is well known the way the call went immediately to the source without hesitation. Other dealership had one ready on the shelf. The expanse of the TSB looks wide across all models and years listed. Indeed, as shared, this maint needs more attention than follow of manuf. schedule, I'm learning this lesson too late. The feedback here is good and that is very clear to me now. The maint minder for the oil was always followed. It's about 9 years old with 55,400miles. I don't think coolant maint carries to the same attention as the oil changes at it should.

Take note as well from the TSB Repair Procedure "..draining the coolant twice", in fact the same instruction is repeated twice. So there's an underscore for a *blank* cleanse here to chase out every ml of residual contaminates. I've seen one comical yt of a guy taking a garden hose at high pressure to clear his blocked heater core - totally different vehicle. The videos leave out some surgical nuances and mandated warning labels. My diy efforts incur blood loss as tradeoff for what's in the wallet or my patience.

I'm on the 3rd radiator for the Honda Pilot. I don't know what's up with that on Honda never told it was a coolant issue or rust, it just developed some fracture on one side and slowly dripped like spot of blood on the garage floor.. uh oh... I didn't dive into that research the same as I've done here. I was told that's where Toyota is a bit different if the coolant is exposed to oxygen it may help to seal a leak. Mechanic advised you can see where it reacts if any leak develops. I didn't go after any kind of hacked radiator seal treatment as such cures may create other problems wasn't a consideration and just had it replaced..again.. but it's 17 years old. Not complaining on that or the 20yr Toyota, consider all the expected owner value has been achieved, if it wasn't for the way the used car market has been of late.

Much thanks for the info and advise here. I'll keep on the owner to get the coolant flushed/replaced, if that fails, then yes will likely end up with the factory method to replace the heater core and for the remainder of the ownership kept to a frequent schedule of coolant replacement as advised.
 
..try to keep this updated.. going in next Monday 6/3 for the coolant flush.. but I did cross the fear of the P011A to service advisor.. he shared past history the sensor trips a week later and down with the core replacement. Service may be for not, but not the first one that tried. I did find some rather obscure postings overseas on the matter much earlier in life for the model year and since this hasn't been driven much to our seeing this maybe much later here. A much older TSB Japan I think had some witches brew remedy using a contraption of fluid pump and citric acid, described the block is crystalized structures forming inside the core, I guess that was abandoned effort not effective...so far the alert code remains silent. I'll send the owner in with the seat cable order too to pick up .. this dealer had the part in stock. I'll try wearing gloves this time and save the cuts on my fingers.

I ran past the earlier post this service has changed to a more frequent schedule.. is it any wonder I'm seeing this as special offer now on the service page?

I'll look for a new ODB reader, sorry not figuring it out or just not really seeing the temp sensor readings on the borrowed reader. I don't know if a single occurrence of temp sensor readings will trip the fault, sustained readings, or n-cycles of drives with readings trip the warning. I guess that doesn't matter if you can feel the difference from the hoses it's enough to the know the condition is present alongside no heat delivery in the cabin.
 
My 2016.5 only has a bit over 50K miles but it looks like I should change the coolant soon. I think I might prefer the Mazda FL22.

After watching the video of how the core can be changed without removing all of the dash I am thinking it might be a good idea to try to drain the coolant directly from the heater core by removing one of the hoses on the firewall. Then I could evaluate the condition of the core by the color of the coolant. I don't see any brown color in the coolant resevoir but if I get a bunch of rust right out of the core I might want to find another heater core before next winter.

I wonder which hose I should disconnect, or if this is a good idea or not?
 
I went out and lowered the glove box door compartment and I can see the heat exchanger. It looks like it should be much easier to remove the core rather than the whole HVAC assembly.
The crimps on the pipe don't appear to maintain the seal. They just keep the o-ring tight against the fitting.
The youtube video says the replacement core was procured via Amazon. Not surprising that Mazda doesn't break down the parts for the HVAC assembly but the parts and labor for replacing the entire unit (and refilling the freon) are really high.
Mazda recommends replacing the FL22 in 10 years, much too late for some people.
 

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