Hello all,
I have a 2016 CX-5 GT with 50K on it and it looks like I'm having the same issue as you are describing. Check Engine light with P011A code (it does not have a block heater). It is intermittent and just today had the computer updated per the TSB for $115. The tech advised me that they had seen this before and the heater core was likely clogged and would require replacement for approximately $1100. From what I'm seeing in this forum it looks like this happens not long after the warranty is out and becomes a "cash cow" repair that happens quite often but running under the radar of most owners. I'm getting some heat but it seems lukewarm with the engine up to temperature so it must be a partial clog. Seems like the reverse-flush idea is a good temporary fix if the debris will flush out. It's sure a lot less costly. I hope Mazda monitors this forum and realizes the secret is out.

 

If all the debris flushes out, there's no reason it can't become the permanent fix. Just add to the flushing an examination and replacement of all heater hoses (large and small) which show any signs of having broken down. That would become a more significant effort if any of the plumbing going through the firewall into the heater core is breaking down. However, I suggest just moving forward with it anyway, because it will need to be done in any case, in order to do the job properly.

 

Mine did blow up. In the shop now with cracked head repair. Within a week of Mazda saying I needed a new heater core for a cost of $1,900, a temp warning light came on. I waited until the car cooled completely down and added fluid. Drove it to a mechanic only to find out my head was cracked.
There are YouTube videos showing how to access the heater core through the glove box. It requires the crimping of two well-sealed metal lines, but looks attainable by a descent backyard mechanic.

 

I have 2014 petrol CX5 with 93,000 miles. With the onset of winter noticed poor heat output. Lots of checks. Reverse flush made no difference. Remove glove box and feel heater pipes only warm, (after repair too hot to touch). Watch flaps move ok in response to heater controls. Do not waste any more time replace heater radiator with aftermarket copper and brass one. This has much wider tubes and will not block. The original is a very efficient heat exchanger with lots of narrow tubes but so narrow that they block. The one that I used had clips rather than crimping and is a well engineered solution. (I do think it is less efficient because of the reduced surface area.) The replacement is probably about 2 hours using U tube advice on how to replace without removing dashboard. Just remove as little as you need to as you go along and do not be afraid to bend the welded bracket that is in the way, it goes back easily! This is one of those problems where you go round in circles and it was always the heater matrix.

 

You wrote that back-flushing while the core was still in the vehicle didn't work, but did you also examine it after removal, including trying to force higher pressure air or water through it? It might be helpful to others if you could find out exactly what's clogging it up, and how much pressure it takes to drive the debris out.

 

Did Mazda fix this problem in their newer models?

 

Hi, the only symptom of this problem was poor heat output. There were no warning lights displayed. Flushing in either direction did show that there was some flow. The heater hoses under the bonnet and the pipes on the heater radiator felt warm but not hot. Because the heater radiator has no valves and is continuous flow these should be too hot to hold. I felt that the cost of replacing it for £122 was worth it over what a dealer would want for a check up. When I compared the back pressure in the old radiator to the new by blowing through it (lung pressure) it was significantly greater. There was no debris and I think that it is narrowing of the tubes due to scale that blocks them. The problem described with symptoms of overheating are more indicative of coolant loss, main radiator blockage, thermostat or head gasket failure. My car is petrol model and relatively simple and the diesel may be more problematic. I would not expect partial blockage of the heater to cause these problems of overheating. An obvious test is to by-pass the heater by joining the hoses that run under the bonnet to a piece of suitable diameter pipe.(a plumbers 15 mm copper U secured with screw clips would be ideal). Run the car from cold and top up the coolant level watching for bubbles. When the level is stable put the radiator cap on. Any problems now are not due to the heater. Run the car at a fast idle and check for coolant temperature in all of the hoses. The copper U and the heater hoses should be very hot. If the car runs normally for a few days with no heater in the circuit then invest in new heater radiator. Only remove what is in the way of the heater matrix extraction! 2 hours!

 

WELCOME TO THE FORUM

I am not sure the use of more air or water pressure in the procedure is recommended to do with anyone except those having experience with cooling systems. And even those that are it is not a way to perform the service! You can very easily destroy other parts or make a simple flushing turn into a disaster. And I would NEVER advise to increase air or water pressure until a clogged cooling system part cleared?

 

Mazda service bulletin 07-007/19 covers this. 07-007/17 is superseded.
This applicable to most of the Mazda range but it is the earlier models that are showing the issue.
Reference to contaminated coolant and need to refill with premixed (presumably deionised) coolant suggests to me that it is scaling of the narrow heater tubes that causes the problem. The onset of my problem at 93,000 miles suggests scaling is a progressive process. I would not fit a secondhand unit for this reason.
It seems that this system needs to be managed properly to protect it!
The 2019 bulletin relates to the coolant concentration of “anti rust” (corrosion/scaling) inhibitors being increased. That is probably the crux of the problem. As time passes deposition occurs on the walls of the heater matrix tubes, blocking them eventually!

 

Well first who is a chemical Engineer on this forum? It would be nice if we had one but as we don't....... ^^^^ how the heck did you conclude that!? There is no information anywhere even with the chemical manufacture that supplies those rust inhibitors has no cautionary about the use that could cause damage or what your somehow concluded? You may want to do a little more research into that and see what there use information is next time? It does take a little digging to find all the resource information and way easier than a TSB!
Please in the future if you or other members are going to quote TSB written for and intended for use by skilled technicians read it completely and understand it completely! And please don't pull only some information you think supports your idea's!
Did you even completely read the TSB and understand all of it? I had to read it a couple times and I am supposed to understand all of that.... LOL Thats what I do for a living for oh about 5 decades now! lol There were parts that should have been SAE edited before approved for publication.

There was no chemical testing of the coolant nor testing the cooling system hard parts to base any conclusion that could be empirical. The TSB was also outlined with several tests to determine the condition and possible solution to remedy the concern. That is basically what TSBs are for. Unfortunately the internet has made available information like TSB that any Tom, DICK Jane and Hairy, can access and think they understand what the information is on them!

I already read that a member blow his breath in a cooling system part and determine its CFM rate comparing a completely different manufactured part. WOW!!!!!!!! LOL REALLY !!!! LOL
Totally disregarding the complete cooling system design and making WILD guesses about how something should be! While it may result in being true the method used is not fundamentally the correct or even a good way to do it!


Just to be clear it truly bothers me when some post information on a thread without doing the research . I feel sorry for the poor members reading it hoping to find a solution to a like problem that thinks it is accurate or empirical in nature or just the correct information will trust the information and act on it!


I know that ATOMIC you may take offense to my posting style and information and based on your username I am going to guess you are over the age 60. Please don't! I am straight to the point, and I don't pull punches! Even in the real world! I can understand "old school" ways of thinking and doing things pertaining to vehicles but the technology of the vehicles (2000 and newer) you and most on this forum are driving are no longer so DIY friendly. Many service procedures now do really require more considered reading FACTORY SERVICE MANUALS or if available Haynes, Chilton, Clymer etc. repair manuals. I suggest to really stop reading TSB's unless you are at least a currently educated auto mechanic, currently meaning in the last 20 years.

ASE



*CONSUMER NOTICE: The information and instructions in this bulletin are intended for use by skilled technicians. Mazda technicians utilize the proper tools/ equipment and take training to correctly and safely maintain Mazda vehicles. These instructions should not be performed by “do-it-yourselfers.” Customers should not assume this bulletin applies to their vehicle or that their vehicle will develop the described concern. To determine if the information applies, customers should contact their nearest authorized Mazda dealership. Mazda North American Operations reserves the right to alter the specifications and contents of this bulletin without obligation or advance notice. All rights reserved. No part of this bulletin may be reproduced in any form or by any means, electronic or mechanical---including photocopying and recording and the use of any kind of information storage and retrieval system ---without permission in writing. © 2019 Mazda North American Operations, U.S

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