Coolant

ColoradoDriver

2014 CX-5 Touring AWD - 132k miles
Contributor
:
Denver, CO
So when I was taking the airbox out of my car to do the tranny fluid drain and fill, I noticed that the reservoir for the coolant was low, but I also noticed that it was kinda brownish in color.

I knew from the service schedule that it was supposedly good for 10 years / 120k miles.

But I don't know...think it might need some service? Currently 5 1/2 years / approaching 72k miles.
 
I would just clean out the reservoir and top up with fresh coolant. The reservoir breathes and that brown is just probably dust. Ed
 
I would just clean out the reservoir and top up with fresh coolant. The reservoir breathes and that brown is just probably dust. Ed

Ok. I'll have to open it up when I get a chance (and its cool) and take a look at the actual fluid. How does one clean out the reservoir?
 
At 91k miles ours is still greenish at the radiator cap. I'd wait to 120k miles before changing.
 
At 91k miles ours is still greenish at the radiator cap. I'd wait to 120k miles before changing.

Ok...I'll actually open it up and take a look inside for the fluid color. It just looks brown from the outside.

That said, it is definitely on the low side in the reservoir. Assuming fluid condition looks fine, just top off some with the FL-22?
 
Ok...I'll actually open it up and take a look inside for the fluid color. It just looks brown from the outside.

That said, it is definitely on the low side in the reservoir. Assuming fluid condition looks fine, just top off some with the FL-22?

Or distilled water.
 
Ok...I'll actually open it up and take a look inside for the fluid color. It just looks brown from the outside.

That said, it is definitely on the low side in the reservoir. Assuming fluid condition looks fine, just top off some with the FL-22?
Coolant should look greenish but not brown. If the coolant looks indeed brown, either someone else added wrong coolant at certain point, or worse, you may have engine oil mixed with coolant. Open up the radiator cap when engine is cold and check the color of the coolant. Also check if you have any sign of oil at the cap neck of radiator.

Yeah always use FL-22 coolant to top off.
 
Coolant should look greenish but not brown. If the coolant looks indeed brown, either someone else added wrong coolant at certain point, or worse, you may have engine oil mixed with coolant. Open up the radiator cap when engine is cold and check the color of the coolant. Also check if you have any sign of oil at the cap neck of radiator.

Yeah always use FL-22 coolant to top off.
Thanks. Will take a look in the morning when it's cold :)
 
That said, it is definitely on the low side in the reservoir.

I think that is normal because the reservoir fluctuates if I'm not mistaken? If coolant becomes pressurized the coolant must go into the overflow reservoir tank. When it cools down over time it goes back into the radiator.

^ At least thats what I thought.
 
I think that is normal because the reservoir fluctuates if I'm not mistaken? If coolant becomes pressurized the coolant must go into the overflow reservoir tank. When it cools down over time it goes back into the radiator.

^ At least thats what I thought.
Yes the coolant level fluctuates in the reservoir depending on engine temperature. That's why you check the coolant level in reservoir when engine is cold.
 
Thanks guys. Just looked at it cold. Fluid was green on the cap. Reservoir definitely dirty on the outside, hence why it looked very brown. So I think it's good.

Level though is just a bit over the L, so maybe still a topoff?
 
Thanks guys. Just looked at it cold. Fluid was green on the cap. Reservoir definitely dirty on the outside, hence why it looked very brown. So I think it's good.

Level though is just a bit over the L, so maybe still a topoff?

I would refer to manual.
 
Over the L is fine. Leave it alone. [emoji106]
Check it again when the cold weather comes.
 
Anywhere between the F and L is fine but if it is only just above L then you might find it drops even lower when the cold weather comes. I personally would take it up to nearer the full mark.
 
Thank you. I will put a little coolant in. Would rather it be at least closer to between f and l instead of just above l.
 
Thank you. I will put a little coolant in. Would rather it be at least closer to between f and l instead of just above l.
Since your coolant in reservoir is low and dirty, you should take it out and throughly clean the inside. Then invest a gallon of Mazda FL22 coolant (~$22) to refill the reservoir to the "F" mark. Depending on the coolant you get, you may need to mix it with 50% of the distilled water. I used to prefer pure coolant but now I prefer the pre-mixed coolant since it's cheaper and much easier to refill or top off the cooling system.

Even if you don't want to clean the reservoir, you still need to add FL22 coolant to the "F" mark when the level is near the "L" mark just like engine oil level. I usually top off any fluids to the "Full" mark if it's below the half between "F" and "L" as I want to have more safety margin and don't want to be living dangerously. BTW, our owner's manual says:

Mazda CX-5 Owner's Manual said:
The coolant should be at full in the radiator and between the L and F marks on the coolant reservoir when the engine is cool.

If it is at or near L, add enough coolant to the coolant reservoir to provide freezing and corrosion protection and to bring the level to F.
 
Since your coolant in reservoir is low and dirty, you should take it out and throughly clean the inside. Then invest a gallon of Mazda FL22 coolant (~$22) to refill the reservoir to the "F" mark. Depending on the coolant you get, you may need to mix it with 50% of the distilled water. I used to prefer pure coolant but now I prefer the pre-mixed coolant since it's cheaper and much easier to refill or top off the cooling system.

Even if you don't want to clean the reservoir, you still need to add FL22 coolant to the "F" mark when the level is near the "L" mark just like engine oil level. I usually top off any fluids to the "Full" mark if it's below the half between "F" and "L" as I want to have more safety margin and don't want to be living dangerously. BTW, our owner's manual says:

My understanding is the Mazda Coolant is premixed. Oh and btw stick with OEM coolant as Mazda advised it will not eat OEM hoses. Aftermarket coolant may or may not be compatible. Might be marketing but I wold not take the chance. Coolant lasts for 120k miles so the price isn't too bad.

Colorado, was the reservoir dirty from the inside versus outside?
 
My understanding is the Mazda Coolant is premixed. Oh and btw stick with OEM coolant as Mazda advised it will not eat OEM hoses. Aftermarket coolant may or may not be compatible. Might be marketing but I wold not take the chance. Coolant lasts for 120k miles so the price isn't too bad.

Colorado, was the reservoir dirty from the inside versus outside?

Dirty on the outside. My entire engine bay is pretty filthy, so I really should have realized. Poppped the cap off, the fluid was green on the cap.
 
My understanding is the Mazda Coolant is premixed. Oh and btw stick with OEM coolant as Mazda advised it will not eat OEM hoses. Aftermarket coolant may or may not be compatible. Might be marketing but I wold not take the chance. Coolant lasts for 120k miles so the price isn't too bad.

Colorado, was the reservoir dirty from the inside versus outside?
Although there're many after-market FL22 coolants available, I'd stick with Mazda FL22 coolant too, especially when we do the top off which is mixing with old OEM coolant. My Mazda dealer carries 3 different kind of FL22 OEM coolants. Not sure if they're all premixed or not.
 
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