2016~2023 CX-9 Coolant Overflow Tank

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2016 Mazda CX-9
Hey everyone,

So I know the 2nd-gen CX-9’s have a closed coolant system. However, when I checked my coolant overflow tank, I noticed the coolant was well below the low fill line. Should this be cause for any concern?

I have taken my car to my local Mazda dealer and had them do a coolant flush; however, they didn’t top up the coolant in the overflow tank to in-between the low and full line. Additionally, they said there’s no leaks, so I’m not sure whether I should be concerned. I’m new to the car community, so if you guys could explain how this process works, that would be amazing!

I’ve added a video below (it’s so bad and I apologize for that) showcasing the coolant overflow tank and how it’s empty. The engine is warm and temperature gauge read 200°F. Since the video didn’t really show my concern clearly, I’ve added two images showing how the expansion tank is empty.

Once again, I would really appreciate it if you guys could explain whether this should raise some concern.

Thank you,
Shawnee
 

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Update:

So I checked the owner’s manual, and the coolant reservoir tank should be filled with coolant between the L and F lines when the engine is cool. I’ve added a screenshot from the owner’s manual regarding this piece of information. I hope this helps other CX-9 owners!

Sincerely,
Shawnee

P.S. this owner’s manual is for the 2016 CX-9, I’m not sure if Mazda changed any information for the CX-9’s between 2017-2023.
 
I don't think anything was changed regarding this info for newer CX-9s. I also had low coolant when cold, but I topped it up and it seems to be okay now.
 
At the Low line when cold is OK, but it was sloppy for the dealership to leave the level where they did for your work. As the book says, between L & H when cold is best to gave some cushion in case of a small leak.

The coolant is due for replacement at 10 years or 120,000 miles. Were you there, or did the crooks at the dealership sell you a service you did not need? The service writers are paid on commission. If they don't sell services, needed or not, they don't get paid and they get fired.
 
Hey everyone,

So I know the 2nd-gen CX-9’s have a closed coolant system. However, when I checked my coolant overflow tank, I noticed the coolant was well below the low fill line. Should this be cause for any concern?

I have taken my car to my local Mazda dealer and had them do a coolant flush; however, they didn’t top up the coolant in the overflow tank to in-between the low and full line. Additionally, they said there’s no leaks, so I’m not sure whether I should be concerned. I’m new to the car community, so if you guys could explain how this process works, that would be amazing!

I’ve added a video below (it’s so bad and I apologize for that) showcasing the coolant overflow tank and how it’s empty. The engine is warm and temperature gauge read 200°F. Since the video didn’t really show my concern clearly, I’ve added two images showing how the expansion tank is empty.

Once again, I would really appreciate it if you guys could explain whether this should raise some concern.

Thank you,
Shawnee
Hello friend.....have a look at this: Engine Coolant Reservoir Level Low, maybe leaking? 2018 CX-9

If you're not aware, have a look at this: Poll - 2.5T Coolant Leak/Engine Replacement

You should keep a close eye on your coolant level after you top it off while the engine is cold.
 
Hey everyone,

So I know the 2nd-gen CX-9’s have a closed coolant system. However, when I checked my coolant overflow tank, I noticed the coolant was well below the low fill line. Should this be cause for any concern?

I have taken my car to my local Mazda dealer and had them do a coolant flush; however, they didn’t top up the coolant in the overflow tank to in-between the low and full line. Additionally, they said there’s no leaks, so I’m not sure whether I should be concerned. I’m new to the car community, so if you guys could explain how this process works, that would be amazing!

I’ve added a video below (it’s so bad and I apologize for that) showcasing the coolant overflow tank and how it’s empty. The engine is warm and temperature gauge read 200°F. Since the video didn’t really show my concern clearly, I’ve added two images showing how the expansion tank is empty.

Once again, I would really appreciate it if you guys could explain whether this should raise some concern.

Thank you,
Shawnee
Why did you do a coolant flush on your 2016 CX-9? Like PTguy said, you don’t need one until 10 years or 120,000 miles.

You should go back to the Mazda dealer and ask them to top off the engine coolant with Mazda’s FL-22 coolant to the “F” line in the overflow reservoir since they did a poor job for the coolant flush.

Even though the owner’s manual says the coolant level is fine between “L” and “F” in the reservoir, but it also says you need to top off to the ”F” with the FL-22 coolant when the coolant level is approaching the “L” mark. I’d always keep the coolant level to the “F” mark when the engine is cold for larger safety margins.

As others have said, you really want to keep your eyes on the coolant level, as this engine could develop the cracked cylinder head and coolant leak is the sign.
 
Hey everyone,

So I know the 2nd-gen CX-9’s have a closed coolant system. However, when I checked my coolant overflow tank, I noticed the coolant was well below the low fill line. Should this be cause for any concern?

I have taken my car to my local Mazda dealer and had them do a coolant flush; however, they didn’t top up the coolant in the overflow tank to in-between the low and full line. Additionally, they said there’s no leaks, so I’m not sure whether I should be concerned. I’m new to the car community, so if you guys could explain how this process works, that would be amazing!

I’ve added a video below (it’s so bad and I apologize for that) showcasing the coolant overflow tank and how it’s empty. The engine is warm and temperature gauge read 200°F. Since the video didn’t really show my concern clearly, I’ve added two images showing how the expansion tank is empty.

Once again, I would really appreciate it if you guys could explain whether this should raise some concern.

Thank you,
Shawnee
Check the collar of the coolant overflow tank, the collar was made with a different plastic is so soft that when the car reaches a high temp the collar starts to deform leaving a small fracture between the collar and the tank, making a coolant seepage that can empty the whole overflow tank. I have replaced this tank twice. Hope this help you.
 
This is very unusual. By the "collar" do you mean the filler neck of the overflow tank? My 2016 seems to that the same plastic material on all parts of the overflow tank. And I haven't driven this car hot & hard in very hot summer temperatures which could change things. (With a previous vehicle I pulled a travel trailer in very hot summer temps at freeway speed including mountains. That's hot & hard.)

In any case...(A) do you watch the coolant temperature gauge? It should be just slightly to the left of the center mark. (B) Do the air louvers in front of the AC condenser and radiator open as they should? (C) Is the radiator fan running as it should...no motor problem? (D) Does the radiator cooling fan come on when it should? It has a thermostatic switch to turn it on.
 
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