2017 CX5 - Coolant Leak?

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2017 CX5 AWD Touring
On a 2017 CX5 with 40,000 miles. I have noticed the coolant level dropping in the overflow. It's a really slow drop but still noticeable. I can't find any drips by the water pump and everything looks dry. Engine oil level is not rising and no overheating so I can't see it being a head gasket.

Anyone else have this issue?
 

Kedis82ZE8

'15 CX-5 GT AWD, '12 GX 460, '07 G35x
Contributor
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'15 CX-5 GT AWD
Any chance the cap is bad, not pressurizing fully and causing an evaporative loss?

Might want to have a pressure test done on the cooling system.
 
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Southwest Ohio
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'19 CX-5 diesel
My 16.5 seems to like the level just a little above the L mark. It never drops below that but anything filled above that level disappears over time into some unknown alternate coolant world through osmosis or sumpin' lol
 
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2020 CX-5 AWD
Do you check the level on a completely cold vehicle each time? And does the level at the radiator cap stay the same?
 
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CX5 GT
depends where you live I think.
My overflow tank loses a bit each year (usually in the very hot months) until it settles a bit on the L mark (as mentioned above)
the extra coolant goes away from the small open pipe from the overflow tank. Or evaporates more or less :)

Its funny though because the car keeps few degrees lower temp in then summer if coolant is on H vs L.

So yearly I just fill it up to the High mark and live with it going down to L eventually. It has never went below L.

I also check my used oil yearly- no coolant in oil and also check for leaks, no leaks.

If it drops for few weeks then it may be an issue. So fill it in and see how long it takea to drop. If its 6mo that should be ok.
 
Last edited:
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2017 CX5 AWD Touring
I check the cold level at the radiator overflow and not at the radiator cap area.

It was at the "L" mark when cold sitting in the garage. Drove it, waited a day, then it's a 1/4" below the "L" mark.

Will test it more this week.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
I think change in ambient temperatures can affect places where coolant can seep out. I've noticed a little seepage around hose clamps in extreme cold weather. I've also had air conditioner seals leak in extreme cold. The dimensions of the mating parts might change, I suppose.
 

madar

Contributor
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2016.5 CX 5 Touring AWD, 2015 SCION XB
I always notice it this time of year with cold weather coming on, no matter what I drive. Level might drop a quarter inch or so. I'm looking at 48k miles.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
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Plano, Texas, USA
My 16.5 seems to like the level just a little above the L mark. It never drops below that but anything filled above that level disappears over time into some unknown alternate coolant world through osmosis or sumpin' lol
My 2016 CX-5 is doing the same. Topped the coolant off 3 times from “L” to “F” mark at my Mazda dealer during new car warranty period. Considering to buy a gallon of OEM pre-diluted 55/45 FL22 coolant and top the coolant off annually.
 

Kedis82ZE8

'15 CX-5 GT AWD, '12 GX 460, '07 G35x
Contributor
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'15 CX-5 GT AWD
I have never noticed mine over the years dropping in recovery tank. I was going to replace coolant this year or last but all that was already done under warranty when they had to pull the motor for the rear main seal replacement.
 
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CX5 GT
list price was about 25 bucks here in AZ. part no is 0000 77 508 E 20 for the long life FL22 prediluted.
You may find it cheaper online or ask dealer to pricematch.
 
My 2016.5 was under the L after I got it from the dealership, brought it back and they topped it off. I check yesterday (10 months later) and it's way under the L again. I just filled with FL22 and going to keep a good eye on it now.
 
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13' CX-5 and 16' Mazda6 both Touring w/Tech/Bose
Did you check near the water pump area for dried green drips? Gotta use a flashlight and really look down there.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
Did you check near the water pump area for dried green drips? Gotta use a flashlight and really look down there.
I was inspecting my belt tensioner for leaks and I noticed a small amount of green residue on one of the pulleys under the water pump. I was a bit concerned but after reading the STB I would guess the leakage resulted from some of the long, hot, cross country trips in temps over 95'F.
 
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13' CX-5 and 16' Mazda6 both Touring w/Tech/Bose
I was inspecting my belt tensioner for leaks and I noticed a small amount of green residue on one of the pulleys under the water pump. I was a bit concerned but after reading the STB I would guess the leakage resulted from some of the long, hot, cross country trips in temps over 95'F.
Keep a close eye on it. What you describe is consistent with green coolant coming from the bleeding hole just behind the water pump pulley. The TSB indicates if no accumulation of crystallized coolant residue then you are fine but if there is accumulation of crystallized coolant to replace water pump.

The problem is the bleeding hole is out of sight hidden behind the black water pump pulley and may have or may not crystallization. You may have to access behind the wheel well to feel/see it.

Back to that bleeding hole. It is designed to provide "steam bleeding" as per TSB and is normal. "When the sliding surface temperature of the mechanical seal is more than 248 °F (120 °C) while driving, a small amount of steam (E) is leaked and bleeds through the bleeding hole (F). After drying, the steam leaves a green coolant deposit near the water pump bleed hole (F). This is a normal condition and does not require water pump replacement. "

In my Mazda6, I noticed fresh new green residue just driving around the block so no way I got it up to 248+ degrees. The water pump was replaced promptly.