2016 CX-9 Signature leaking coolant

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Mazda 2 touring
Hey guys,

This weekend the CX-9 started leaking and burning coolant. I took a look at the engine bay and I couldn’t find a leak around the any of the hoses. However, it seems to be leaking from the firewall side. I’ve made an appointment with the dealer, for this coming Saturday. I’ve been reading through the forum and this seems to be a problem, that is affecting the 2016 model years.

I’ll update as I learn more.

2016 signature
39,000 miles
 
Solution
Hey guys,

So I dropped off the CX9 today and this is a known issue (2016 model years). The service assistant confirmed this, even before I took in the car. Once the car was inspected, they determined a new engine would be required. However, they are in back order and I’ll get more information on Monday. I’ll try to get photos of the engine and more details if possible.

I think my build date is March or April 2016.
There can be quite a difference. As @sm1ke said, check it at the same time, at the same heat every time. If you are leaking into the cylinder, you wouldn’t have any coolant on the ground as it would be burning and sent out the exhaust. My car right before this was leaking into the cylinder. There was a slightly fruity smell every time I parked it in the garage and I had to top off coolant about once every other week. No pools on the ground when it was parked
Now that you mention it, I can smell a strong odor as well during cold start. Will this leak accelerate engine failure? What will happen if this thing keep leaking into cylinder for a long period of time? I really like the car and plan to using it for at least 5 years. And now it is only 6 months. And complain to dealer for engine replacement would impossible thing to do in my country.
 
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On my car, when the reservoir level is checked after I get to work (hot engine), it's right below the top of the "F". If I check it around noon (cool engine, about 5 hours later), the level is about an inch and a half below the full mark.
That is still ok I think. Mine is almost near "E" mark. I will get you a photo tomorrow morning.
 
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sm1ke

Work In Progress..
Moderator
Contributor
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Canada
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'18 CX-9 Signature
That is still ok I think. Mine is almost near "E" mark. I will get you a photo tomorrow morning.

If there are no other symptoms (coolant smell, pooling/drip marks on the floor), watching the fluid level will help you determine if there is a leak. Just be sure to be consistent about when you check the level.
 
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If there are no other symptoms (coolant smell, pooling/drip marks on the floor), watching the fluid level will help you determine if there is a leak. Just be sure to be consistent about when you check the level.
I just went through this with my 2016, I first noticed it when I was coming out of a car wash and the car overheated, I never once had a puddle of coolant on my garage floor, or in parking lots. It can be very difficult to notice without checking coolant regularly. I have a replaced engine, I could be wrong but I haven’t seen this happen on newer model years than 2016, so hopefully Mazda fixed the issue on the newer engines. It also could just be that many people aren’t at high enough mileage yet on newer model years.
 
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sm1ke

Work In Progress..
Moderator
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Canada
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'18 CX-9 Signature
I just went through this with my 2016, I first noticed it when I was coming out of a car wash and the car overheated, I never once had a puddle of coolant on my garage floor, or in parking lots. It can be very difficult to notice without checking coolant regularly. I have a replaced engine, I could be wrong but I haven’t seen this happen on newer model years than 2016, so hopefully Mazda fixed the issue on the newer engines. It also could just be that many people aren’t at high enough mileage yet on newer model years.

Very true, with all of the undercarriage plastic shields, the pooling might be easy to miss. It seems the best way to keep track is to check your coolant level periodically (if you think there may be an issue).

I believe I've seen one or two reports of this issue happening on a 2017 and a 2018. Possibly mine (2018 w 57.5k kms) as well.. I have an oil change coming up, and I plan to send another sample out for analysis to compare with the first, but since topping up the coolant, I don't think the levels have dropped, and I have none of the other symptoms as far as I can tell (crossing my fingers).
 
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This thread is news to me, but I’m glad I found it. I’ve got a ‘18 GT, with ~39k miles. I went through a whole ordeal with the dealer about cylinder misfires that they couldn’t solve, and I ended up replacing the spark plugs myself and the problem *mostly* went away. I’ve randomly smelled coolant from my car after long drives, but dismissed it because I never saw anything pooling or leaking. My coolant level last night when the car was cold is about 1/2 inch above the “LOW” mark, so I’ll keep my eyes on it. No overheating, but still the occasional studder that feels like misfiring but no CEL or anything. Some days it drives like new, and some days it drives like poo….

Based on this, is there a TSB or something I can take back to the dealer and say “HEY LOOK AT THIS…” because they repeatedly just told me “we can’t find a problem” and sent me on my way until the CEL came on in front of them for a cylinder 3 misfire. They claim they did all sorts of tests (including a compression test) and still nothing wrong…
 
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zoomsd

Member
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2016 Mazda CX-9 GT
November 2021

My CX-9 2016 GrandTouring also experienced the coolant leak with Coolant warning light on and the coolant level in the reservoir was very low (below the LOW mark). It has just under 80K miles. I brought it the local Mazda dealership. First, they diagnosed and replaced the thermostat. I brought it home and a day later of driving, the Coolant warning light came back.

I had to add more coolant and took it back to the dealership and this time the service advisor asked me to leave the car there longer for more detail diagnosis. They tore down the engine and found a crack in the cylinder head. They are working with my extended warranty company to get an approval for the repair.

Instead of having Mazda stepped up and replaced the engine (or at least long block), I was told I have to go through my extended warranty company first as Mazda will reject the request if they know that customers bought extended warranty. I would love to have the whole engine (or at least the long block) replaced as it seems to be an issue that Mazda is aware of.

Will keep everyone posted how the repair goes. The service advisor also mentioned there might be TSB(s) coming out for this coolant leaking issue.

The car has been in the shop for a couple weeks. The dealership was so kind to lend me a 2021 CX-9 loaner (which looks pretty much the same as my 2016 except for a few upgraded features:360 camera view, Android Auto/Apple Carplay, wider LCD screen).
 
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My 2016 Signature with 94,000 miles was found (by my local auto repair shop during a routine oil change, no visible leaks) to have coolant dripping down the firewall side of the engine, it was traced to the highest point and coolant was found collecting beside the exhaust manifold/turbo hot air inlet. No sign of failed hoses or failing coolant pipes. Before I could get it to the dealership, the coolant temperature light began to flash, then warnings that the engine was overheating and finally the car was inconsistently slowing itself down and resuming normal speed with and without warnings. Meanwhile, the coolant level is full and the engine temp and radiator are at or below 200 degrees. I am having it towed to the dealer tomorrow. My extended warranty is expired. I love this car and planned on driving it a long time. How many people have had this issue fixed without getting a new engine? Or major money investment to get it fixed?
 
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yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
November 2021

My CX-9 2016 GrandTouring also experienced the coolant leak with Coolant warning light on and the coolant level in the reservoir was very low (below the LOW mark). It has just under 80K miles. I brought it the local Mazda dealership. First, they diagnosed and replaced the thermostat. I brought it home and a day later of driving, the Coolant warning light came back.

I had to add more coolant and took it back to the dealership and this time the service advisor asked me to leave the car there longer for more detail diagnosis. They tore down the engine and found a crack in the cylinder head. They are working with my extended warranty company to get an approval for the repair.

Instead of having Mazda stepped up and replaced the engine (or at least long block), I was told I have to go through my extended warranty company first as Mazda will reject the request if they know that customers bought extended warranty. I would love to have the whole engine (or at least the long block) replaced as it seems to be an issue that Mazda is aware of.

Will keep everyone posted how the repair goes. The service advisor also mentioned there might be TSB(s) coming out for this coolant leaking issue.

The car has been in the shop for a couple weeks. The dealership was so kind to lend me a 2021 CX-9 loaner (which looks pretty much the same as my 2016 except for a few upgraded features:360 camera view, Android Auto/Apple Carplay, wider LCD screen).
It’s a known issue now with the 2.5T leaking coolant due to cracked cylinder block. Mazda’s solution for the problem is to replace the engine. But there’s a long wait to get a new / rebuild engine.

Poll 2.5T Coolant Leak/Engine Replacement. What can be done to prevent?
 
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yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
My 2016 Signature with 94,000 miles was found (by my local auto repair shop during a routine oil change, no visible leaks) to have coolant dripping down the firewall side of the engine, it was traced to the highest point and coolant was found collecting beside the exhaust manifold/turbo hot air inlet. No sign of failed hoses or failing coolant pipes. Before I could get it to the dealership, the coolant temperature light began to flash, then warnings that the engine was overheating and finally the car was inconsistently slowing itself down and resuming normal speed with and without warnings. Meanwhile, the coolant level is full and the engine temp and radiator are at or below 200 degrees. I am having it towed to the dealer tomorrow. My extended warranty is expired. I love this car and planned on driving it a long time. How many people have had this issue fixed without getting a new engine? Or major money investment to get it fixed?
Coolant is dripping down the firewall side of the engine? Unfortunately this’s the typical symptom of coolant leak due to cracked cylinder block. See my previous post above.
 
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2010 CX-9 GT
Certainly sounds like a cracked cylinder head. If you have coolant all the way up at the exhaust manifold, it's probably coming from the head.

Good luck. Mazda has been stepping up and covering these, even those that were out of warranty.
 
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truckster

2023 CX50 Turbo PP
Mazda recently put out this TSB for coolant leak because of cracks in the cylinder head.
As reported by many here it seems to affect the 2.5T 2016-2020 CX-9 as well as 2019-2020 CX-5 and 2018-2020 Mazda6
I would assume it applies to the '21 as well except there probably aren't any with enough miles on them to have started complaining about it yet. That is unless it has been determined that they changed something in the design of the '21 engines. Either way it's a "wait and see" scenario
 
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Mazda CX-9 Grand Touring 2016
So, a good look at the oil will be warranted often, as well as a close check of the coolant level at a consistent temperature. Detergent motor oil is designed to emulsify water in the oil. The oil will look milky. (Emulsified watery oil lubricates better than water or antifreeze that settles to the bottom of the oil pan and gets picked up first by the oil pump when starting.) If there is any doubt, a $30 lab test for coolant in the oil, among other tests, may be money well spent. https://www.blackstone-labs.com/engine-types/gasoline/

An alternative to waiting for new engine parts is to add some cooling system leak-stop additive, change the oil, and trade the car in to a Mazda dealer, or a multi-brand dealer that includes Mazda. (We want the next owner of the car to have a Mazda dealer they bought from to be the one they complain to.)
 
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I would assume it applies to the '21 as well except there probably aren't any with enough miles on them to have started complaining about it yet. That is unless it has been determined that they changed something in the design of the '21 engines. Either way it's a "wait and see" scenario
I don’t know that’s true. There’s a specific “manufactured before” date on the TSP, which implies they had a point where something changed. Maybe I’m overthinking it, but given how long some of these issues took to develop, I’m not sure they can validate any of their changes corrected the problem.
 
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CX-9 CX-5 MSM
So, a good look at the oil will be warranted often, as well as a close check of the coolant level at a consistent temperature. Detergent motor oil is designed to emulsify water in the oil. The oil will look milky. (Emulsified watery oil lubricates better than water or antifreeze that settles to the bottom of the oil pan and gets picked up first by the oil pump when starting.) If there is any doubt, a $30 lab test for coolant in the oil, among other tests, may be money well spent. https://www.blackstone-labs.com/engine-types/gasoline/

An alternative to waiting for new engine parts is to add some cooling system leak-stop additive, change the oil, and trade the car in to a Mazda dealer, or a multi-brand dealer that includes Mazda. (We want the next owner of the car to have a Mazda dealer they bought from to be the one they complain to.)
Coolant stop leak in a modern motor will destroy your engine. The coolant passages are so small they will become clogged. If you want to blow your engine, and void your warranty stop leak is a great way to do it.
 
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Mazda CX-9 Signature
In case anyone is wondering how CX-9 looks like without its engine & trans.
 

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