There are a host of corrosion/scaling inhibitors on the market that are added to cooling fluids.
Various types of triazoles compounds are used (TTA - BZT- MBT) which are effective copper and copper alloy corrosion inhibitors.
They form a protective film on the metals surface (Cu2O)especially in the heat transfer units like the radiator and the heater core.
But they also bond with dissolved copper ions in solution and ANY of those particles will eventually drop out of solution for any fluid.
There is no way to tell what type or how much metal is suspended in solution without doing a chemical testing of the fluid.
Eventually any particles in suspension in any fluid will eventually drop out and clog up the mechanism they are in (like my arteries).
Generally speaking, the smaller the openings and larger the particles the faster this process occurs.
That said each vehicle and cooling fluid manufacturer has their recommended schedule for replacement of these fluids.
The vehicle manufactures often recommend changing the fluid more frequently than the fluid manufacturers do.
Time for some red wine to alleviate some of my system build-up.

 

MR Lobstah...............I am always pleased to see a member that actually looks into a subject or even perhaps has empirical knowledge to post!
As many DIY, professional service shops and dealerships seldom have done regarding crankcase oil, transmission and differential fluids and even. YUP coolant! If simply having had a sample analyzed would have resulted in showing all the contents good, bad and questionable. With regards to coolant most of the samples I had analyzed over the years indicated the failure on the owner of the vehicle to do the minimum service recommendation's and also adding less than the preferred liquids to the colling system which cause the deuteriation of the components in the colling system as well the coolant itself.

One thing that caused a great debate on another automotive forum (not MAZDA) and finally the administrator closed the thread and then deleted it was when I commented that mixing any coolants even when they claim to be compatible can have negative long-term effects on the cooling system. Some of those negative effects is the breakdown of the chemical agents added to the coolants used to reduce or prevent corrosion of vital cooling system parts. Basically, mixing coolant brands is not the best idea IMHO

On my own personal engines, the coolant gets change depending on the service operation of the engine. Generally, the longest I go to is 3 years and no more than 50K miles engines) before a compete fluid and cooling system cleaning. It takes about 2 hours from start to finish. In between if I add any coolant, it is always my mixture of water and 100% coolant verified by the use of a refractometer that measures coolant to water % .

 

Hi, I'm hoping someone here can help me figure out what to do. I'm definitely having this heater core issue on my Cx-5. My mechanic quoted me $2700 to replace the heater core. I have yet to talk to the dealership or anyone at Mazda because I'm not sure what to say. My Cx-5 is 10 years old (2014), past it's warranty. I have no idea how to handle this situation without getting absolutely creamed bc it's obvious I don't know anything about cars. please help! How to address this at the dealership? Do I even qualify for reimbursement of any kind? Should I just not even bother going there? I've been to two mechanics already and it's such a big waste of time

 

Ask your mechanic to flush the heater core rather than replace it. That had worked for me and a friend who has a 2015 CX-5 which had same issue as my 2014 CX-5. Drain cooling system before doing heater core flush and after flush add new coolant to heater core and radiator. Takes about 2.5 hours to do properly.

 

Ive been experiencing this same issue and just had the heater core flushed yesterday. Today the engine light is back on. It looks like I’m going to have to replace the heater core.

 

After reading all of the above, it appears that the issue is deteriorating heater hoses causing the problems. How often do people replace these? To me, they are a maintenance item..

 

I'm dealing with a lot of the same issues with my 14 CX5. low/little heat, check engine light related to coolant temperature issues. I replaced the heater core using the under-the-glove-box method, but can't seem to get the old hoses to seal into the new core. I can't figure out how to get the hose/lines through the firewall to just replace these all at once. Lots of plastic housing/stuff there that I can't figure out how to get out of the way to open a space big enough to force the hoses through. Anyone done this?
THANKS!

 

Looks like there's a retaining clip/plate part that locks the hoses in place. I think that I figured out how to remove it.
Stephen

 

2016 Mazda CX-5 with 52,000 miles. Had DTC Po11A and gold CEL.

When I saw the CEL, I scanned code and got P011A. I went to Mazda dealer who charged me $200 to review the car and they diagnosed this as a CLOGGED HEATER CORE. Charge to fix was $2,700. I asked them for a less costly estimate and apparently, Mazda won’t do anything for a nine-year-old car; not even for one with such low mileage.

What really got to me was the illumination of the CEL for something that has nothing to do with processes for which the CEL should be turned on. The CEL is to alert you to trouble with the engine, drivetrain, or emissions systems. You don’t get a CEL with a TPMS light or an AC system that’s low on refrigerant, so why have a CEL for something as benign as a clogged heater core? It has no effect on car operation. This I found particularly troublesome, because most of us have to pass a semiannual SMOG test to maintain car registration, and with an illuminated CEL, no shop will smog a car. I feel that we’re held hostage by Mazda to pay a ridiculously high price to fix a problem that shouldn’t even exist.

I read over Mazda’s repair procedure and thought it idiotic to have to remove the whole dash and the HVAC console just to R&R the heater core. I looked through the glove box opening and saw the core and feeder tubes. I also saw a steel strut (structural & welded) which would have to be moved to fully access the core. So I considered alternatives to replacing the core myself.

After some research, I thought I could fix this with a flush. I started with the strongest flush I know of, Irontite. After that, I flushed three times with distilled water, which ran crystal-clear, and a couple days later, the CEL went off and the DTC (permanent at that time) had been cleared.

I then added a gallon of white vinegar go the distilled water in the cooling system and ran the car a couple hundred miles. The clear liquid had turned cloudy, presumably from debris from the cleaning, and a little reddish, which I presume was residual Irontite that had been trapped in clogs and had come loose in the vinegar flush. I then flushed the system with distilled water until crystal clear again and was amazed to see the CEL with P011A DTC returned. I waited until I had done a few cold-restarts to see if the CEL would be extinguished. Two days later, it was and the DTC had been cleared by the computer.

I was concerned about the returned DTC & CEL, so I decided to do a reverse flush. I disconnected the heater hoses at the firewall and connected other hoses to do the flush process. I connected a garden hose to the core’s output side and had the input side run into five-gallon glass jars so I could evaluate the results.

I ran on low water pressure for couple minutes, then increases pressure to where I thought it would be safe, and not blow the O-Rings that seal the tubes to the core. The first jar was cloudy with a lot of suspended black chunks; presumably deteriorated radiator hoses. After that, the water got clearer. I then continued this until the water ran clear and there were no more black bits in the water.

When I reconnected the heater hoses, I had an idea: why not keep the reverse flow? I attached the hose from the engine/ECT1 to the lower tube at the firewall, the core output, and the hose going to ECT2 to the upper, core intake tube.

Now, heat on the passenger side is still blowing really hot, and the driver’s side very nearly the same…. So, we’ll see how long this works.

I formed a letter to Mazda USA and the dealer, telling them that I believed this to be a defect in design. Why would they use cores that clog so easily and then add an ECT2 which has no other purpose than to monitor the heater core? And why would they have the computer turn on a CEL for something that’s out of the responsibility of the CEL? MAZDA ignored my letter… Well, I actually considered my letter to be a ****-you to Mazda, anyway.

I expect to replace this Mazda soon with a Toyota or Lexus, two brands I’ve relied on for half a century.

You can see our 1991 Toyota Previa which we bought new pictured here...

 

A 2016 Mazda CX-5 with 52,000 miles means it spent the majority of its life sitting still.
Any fluid in a closed operating system that doesn't get regularly used, or changed, is likely to cause issues.
Your heater core being one of them.
Enjoy your new Toyota or Lexus and their forums.