Mazda CX-9 Common Problems

The CX-9 is Mazda's seven-seat SUV, sold here from late 2007 to 2023 in two generations. The TB (2007 to 2015) uses a Ford-derived 3.7-litre V6 (MZI) and a six-speed Aisin automatic. It was AWD only at first; front-drive versions arrived in 2011. The TC (2016 to 2023) switched to a 2.5-litre turbo four (SkyActiv-G 2.5T, PY-VPTS) with a six-speed auto, again in FWD or AWD. Both are spacious, well-built family cars, but each has a reported weak spot: the TB's AWD transfer case and internal water pump, and cylinder head coolant leaks on some earlier TC turbos. Most other complaints involve brakes and electrics.

Transfer case failure (TB AWD, 2007 to 2015)

The power transfer unit (PTU), which sends drive to the rear wheels on AWD models, is the TB's best-known weakness. Mazda set no oil change interval for it, and the oil breaks down with heat, causing noise, leaks, overheating and gear wear. Metal debris can then damage the splines between the gearbox and transfer case, which can mean a new automatic as well. Failures have been reported from about 70,000 to 150,000 km. In the US, Mazda extended warranty cover on units built from mid-2009 to late 2013, but that may not apply here. Some workshops suggest changing the PTU oil around every 60,000 km, or sooner if towing. Owners report replacement bills of roughly $4,000 or more.

Internal water pump failure (3.7 V6, TB, 2007 to 2015)

The V6's water pump sits inside the engine, behind the timing cover, and is driven by the timing chain. When its seal fails, coolant can leak into the oil rather than onto the ground. Signs are coolant loss with no visible leak, milky or thinned oil, a sweet smell and overheating. Ignored, it can destroy the engine bearings. Most reports come from US owners, who rate it one of the model's costliest failures, mostly on high-kilometre cars, but the engine is the same here. Replacing the pump means removing the timing chain, so expect roughly $2,500 to $4,500 at a specialist, and much more if the engine is damaged.

Brake booster and front ball joint wear (TB, 2007 to 2013)

The brake booster diaphragm on earlier TBs can harden and tear, especially in hot climates. The pedal first feels harder, then a hiss from the driver's footwell appears as air leaks, and some owners report a sudden loss of assistance. Mazda extended the warranty on the booster in the US, but that extension may not apply here. Front lower ball joints on earlier cars can corrode when water gets in; this was recalled in the US, so have a dealer check what applies to the car here, and check for play and split boots. A pair of lower arms is roughly $500 to $1,000 fitted.

Cylinder head coolant leaks (2.5T, TC, 2016 to 2020)

Some earlier TC turbos are reported to crack the cylinder head around the exhaust manifold, leaking coolant. Symptoms are a falling coolant level, a sweet coolant smell in the cabin, a low coolant or overheat warning and, in some cases, a heater that blows cold. In the US, Mazda is reported to have issued a 2021 service bulletin describing these cracks, said to cover CX-9s built before about mid-2020, and at least one Australian owner has reported the same fault. The repair is a new cylinder head, which on some cars means removing the engine; out of warranty, expect several thousand dollars. On a car with full dealer servicing, ask Mazda whether it will contribute.

Premature brake wear and corrosion (TC, 2016 to 2023)

Some TC owners report pads and rotors wearing out early, and rotors or calipers corroding on cars that sit for long periods or do short trips. US owner complaints also list premature brake wear among the top issues for 2016 cars. It is a heavy car, so brakes work hard, especially when towing. Check rotor lips and pad thickness, and budget roughly $600 to $1,200 for pads and rotors on one axle.

Stop-start and electrical faults (TC, 2016 to 2019)

Some owners of 2017 to 2019 TCs report i-stop and battery management faults, including a stall mid-turn with error messages, plus faulty displays and reversing cameras, mirrors that will not fold and false driver-assist warnings. A 2019 recall covered cars sold from October 2017 to February 2019 whose wiring connectors could lose grip, causing false warnings, indicators that may not work, no restart and, in a crash, a front passenger airbag that may not deploy as intended. A dealer scan and software check is the first step and a modest cost; a new screen or camera costs more.

Recalls and safety

TB recalls include a Takata passenger airbag inflator on cars built before 30 April 2013, and front strut lower bolts that may not have been tightened correctly on some cars sold from 2013 to 2015, which in the worst case could let the strut separate from the steering knuckle. TC recalls cover the wiring connector fault above (2017 to 2019) and a low-pressure fuel pump that can deform and stall 2017 to 2019 cars. Make sure the Takata work has been done on any TB. Ask a Mazda dealer to check the VIN for open recalls, and see our recalls page.

Buying a used Mazda CX-9? What to check

• Transfer case: On an AWD TB, ask when the PTU oil was last changed. Listen for whine or grinding under load and look for oil leaks around the unit.
• Coolant and oil: Check the coolant is at the mark with no sweet smell, and look under the oil cap and on the dipstick for milky residue.
• Water pump history: On a TB past 150,000 km, ask whether the water pump and timing chain have been replaced and get the invoice.
• Brake booster: Press the pedal with the engine off and then running. A hard pedal or a hiss from the footwell points to the booster.
• Head cracks: On a 2016 to 2020 TC, ask about coolant top-ups or head repairs, and look for crusty coolant residue at the back of the engine.
• Suspension and brakes: Check the front ball joints for play and split boots, and inspect rotors and pads for heavy wear or corrosion.
• Gearbox: Check for harsh or delayed shifts, especially out of Park. A few TC owners report gearbox replacements.
• Electrics: Test every screen, camera, mirror and door, check i-stop works, and have the car scanned for stored codes.

Run a Carify PPSR check for finance owing and write-off records, and take our Mazda CX-9 buying checklist to the inspection.

The verdict

The best used CX-9 is a TC built from mid-2020 on, after the period reportedly covered by Mazda's US cylinder head bulletin; see our 2021 CX-9 page. Earlier TCs are still good buys if the coolant level is stable and the service history is complete. A TB is a lot of car for the money, but budget for the transfer case and water pump on AWD cars past 100,000 km. A front-drive TB (2011 on) avoids the transfer case altogether. Avoid any TB with an unknown PTU history, overheating or milky oil.