About this problem
Coolant carries heat away from the engine to the radiator. Leaks from hoses, the water pump, the thermostat housing, the radiator or internal gaskets let the level fall until the engine overheats. Owners usually notice a sweet smell, puddles, a low-coolant warning or a temperature gauge climbing. Driving an overheating engine even a short distance can warp the cylinder head.
Across all owner complaints filed about the Mazda CX-9 since 2012, 237 (29.2%) describe coolant leaks, making it the most reported problem we track on the CX-9. The reports cluster on the 2016, 2017 and 2018 model years, and the 2018 drew the most, with 71. It tends to show up at higher mileage: half of the owners who gave a mileage were between 73,000 and 116,000 miles. One report describes a crash or fire linked to it. No recall covers it, but Mazda has sent dealers service bulletins about it, listed below.
What owners report
Owners of 2016 to 2018 CX-9s with the 2.5-liter turbo report coolant loss and overheating from a leaking cylinder head. Earlier V6 models report internal water pump leaks.
How it gets fixed
Mazda replaced many cylinder heads under warranty. V6 water pump repairs require replacing the timing chain too.
Typical cost: A cylinder head costs $2,000 to $4,000 out of warranty.
Complaints by model year
In owners' words
"Water pump failed and impacted my engine as well. I just brought my car in as well 10/20/2020 no mention of this issue."
2013 Mazda CX-9
"Water pump defect that led to pump failure, which led to catastrophic engine failure without any prior warning. The defect is in the internal chain-driven water pump. The pump is meant to circulate coolant through the engine while the engine is running."
2014 Mazda CX-9
"My Mazda 2017 CX 9 apparently had a coolant leak. When we had our oil changed, we were told it looked like it was leaking from behind the turbo booster."
2017 Mazda CX-9
Excerpts from public owner complaints filed with the National Highway Traffic Safety Administration, lightly trimmed.
Service bulletins and warranty extensions
Mazda has sent dealers 21 bulletins that mention this problem on the CX-9. A bulletin tells technicians how to fix a known fault. It is not a recall, so the repair is usually free only while the car is under warranty or covered by an extension.
CSP11 - COOLANT LEAKS AT CYLINDER HEAD WARRANTY EXTENSION For certain 2019-2020MY CX-5, 2016-2020MY CX-9, 2018-2020MY Mazda6 that are equipped with SKYACTIV-G 2.5T engine, the warranty coverage for specific repair of the coolan...
Dear Mazda Owner: You are receiving this notice because Mazdas records indicate that your 2019-2020 CX-5, 2016-2020 CX-9, or 2018-2020 Mazda6 vehicle was equipped with a SKYACTIV-G 2.5T (Turbocharged) engine (Covered Vehicle).
There is a concern that some water pumps are being replaced that are not faulty, due to signs of a very small coolant leak from the bleed hole.
This Service Alert supersedes the previously issued SA(s) and TSB(s) listed below: The changes are noted in Red.
Currently, the instructions on MGSS recommend the use of Loctite 962T or equivalent when installing a SKYACTIV cylinder head, but it is no longer available.
A new cylinder head assembly for service parts has been newly established for SKYACTIV-G 2.5 with cylinder deactivation when replacement is needed.
Before you buy a CX-9
- Check the coolant level when cold.
- Look for coolant residue around the engine.
- Ask whether the cylinder head has been replaced.
Questions
Which Mazda CX-9 years have coolant leaks?
Complaints are highest for the 2016, 2017, 2018 model years. The 2018 drew the most, with 71 reports.
At what mileage does it usually start?
Among owners who gave a mileage, the middle figure was about 90,000 miles, and half reported it between 73,000 and 116,000 miles.
How much does it cost to fix?
A cylinder head costs $2,000 to $4,000 out of warranty.