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Reliability report · 2018 Mazda CX-9 · Updated July 2026 · ~$2,600/yr fuel · what it costs to keep →

The loudest gen-2 year — the cracked-head coolant leak peaks here, and two recalls sit alongside it.

The 2018 has the biggest complaint file in the entire second-generation range, and it is concentrated on one system: the 2.5-liter turbo's cylinder head cracks behind the exhaust manifold and leaks coolant, and several owners report the crack propagating into the turbocharger and exhaust manifold around 85,000-90,000 miles, with catastrophic engine damage when overheating goes unnoticed. This is the same defect as 2016-2017, at its loudest.

It also carries two safety recalls: 21V875 (Mazda 5321K) for a Denso low-pressure fuel pump whose impeller can crack and cause a stall, and 19V403 (Mazda 3419E), unique to the 2018 CX-9, for a wiring harness that can disable the passenger airbag, turn signals, and/or the engine-start system. Both are free. The coolant-leak repair is covered by CSP11 — a Customer Service Program extending the powertrain warranty to 10 years or 120,000 miles — if the car is still in window. This is a Squawking year: buy it with eyes open, inspect the engine hard, and confirm both recalls are closed and CSP11 status.

Evidence: 124 NHTSA complaints · 2 recall campaigns · 7 mechanic & forum sources

Canary status

Squawking

What that means: 124 federal complaints — the largest file of the second-generation CX-9 — overwhelmingly the 2.5-liter turbo's cracked cylinder head leaking coolant, and here it also shows as a cracked turbocharger and exhaust manifold. Two safety recalls (a fuel pump and a 2018-specific wiring harness) sit on top. Mazda's CSP11 warranty extension covers the coolant leak to 10 years/120,000 miles. A great SUV with the most to inspect for of any year.

CalmChirpingSquawkingFainted

124

Federal complaints

2

Recalls

$7,614.63

Same-engine head-crack repair (mechanic video, another Mazda)

Known issues

Ranked by the cost of ignoring them. Every claim carries its source.

Cracked cylinder head / turbo / exhaust manifold — coolant leak (CSP11 warranty extension)

major
  • 2.5L turbo (SkyActiv-G)

The defining 2018 failure and the bulk of the file. The 2.5-liter turbo's cylinder head cracks at a stud bolt hole behind the exhaust manifold and leaks coolant; on 2018s owners repeatedly report the crack reaching the turbocharger and exhaust manifold too, typically around 85,000-90,000 miles, with overheating and — if missed — a ruined engine. Mazda's CSP11 extends the limited powertrain warranty to 10 years or 120,000 miles for this exact coolant leak (with reimbursement), and it covers 2018. Inspect for coolant residue at the back of the block near the firewall, confirm any head/turbo replacement history, and check the CSP11 window. Out of window, this is a several-thousand-dollar repair.

Head/turbo repair if outside CSP11 (owner/mechanic reports)

several thousand

Same-engine head-crack repair (mechanic video, another Mazda)

$7,614.63

If CSP11 window applies

$0 (covered)

Sources: NHTSA complaint database, 2018 Mazda CX-9 · NHTSA recalls + manufacturer communications (19V403, 21V875, CSP11 windows, campaign documents) · Independent mechanic and owner/specialist channel transcripts (CX-9 second generation, 2.5T)

Wiring-harness recall — passenger airbag / turn signals / no-start (19V403, 2018-only)major

A recall unique to the 2018 CX-9: 19V403 (Mazda 3419E). The wiring harness may disrupt electrical communications and disable the passenger frontal airbag, the turn signals, and/or the engine-start system — a serious safety defect (the airbag may not deploy in a crash). The remedy is a free wiring-harness repair; the recall began July 26, 2019. Confirm this is completed by VIN before you buy.

Sources: NHTSA recalls + manufacturer communications (19V403, 21V875, CSP11 windows, campaign documents)

Low-pressure fuel-pump recall (21V875)moderate

The second 2018 recall: 21V875 (Mazda 5321K), covering 2018-2019 CX-9 (among several Mazda models). The impeller inside the Denso low-pressure fuel pump can crack and deform, causing the pump to fail and the engine to stall — a crash risk. The remedy is a free fuel-pump replacement; owner letters were mailed July 18, 2022. Confirm completed by VIN.

Sources: NHTSA recalls + manufacturer communications (19V403, 21V875, CSP11 windows, campaign documents)

2018 is the peak of the cracked-head file — coolant leaks, cracked turbos, overheating — with two recalls on top and the CSP11 warranty extension as the safety net.
7 mechanic & owner sources

Open recalls

Free fixes at any Mazda dealer. Run the VIN — “completed” isn’t always completed.

  1. 19V403Wiring harness may disrupt electrical communications and disable the passenger frontal airbag, turn signals, and/or engine-start system (2018 CX-9 specific). Free wiring-harness repair; recall began July 26, 2019. Mazda code 3419E.open
  2. 21V875Denso low-pressure fuel-pump impeller may crack and deform, causing pump failure and engine stall (2018-2019 CX-9, among multiple Mazda models). Free fuel-pump replacement; letters mailed July 18, 2022. Mazda code 5321K.open

What it costs to keep

The purchase price is what you negotiate. These are the numbers you live with afterward — each one sourced, none of them blended into a fake total.

The ownership picture — 2018 CX-9

Three sourced numbers. No fake total.

Fuel

24 MPG combined (22 city / 28 highway) for the FWD, 2.5L turbo on the EPA federal fuel-economy test.

Source: FuelEconomy.gov (EPA) — EPA’s federal fuel-economy test, recomputed with current gas prices. EPA record 39183 (CX-9 2WD).
Other builds EPA lists: 4WD, 2.5L turbo 23 MPG.

$2,600/yr

at $4.15/gal · 15,000 mi/yr · 55/45 city/hwy · pulled Jul 12, 2026

Theft

Stolen at about the average rate.

Source: HLDI — the insurance industry’s loss-data institute — HLDI whole vehicle theft losses, 2016–18 models, published May 2019 (report WT-18). 100 = the all-vehicle average. Series read: Mazda CX-9 4dr 4WD.
Other series: Mazda CX-9 4dr 73, where 100 = average.

101 vs 100

1% above average

Repair risk

What this specific year is known to need. Pulled from the issues above — the repairs owners actually report, at the costs they report them. Averages from other sites blend every year together; these are this year’s own numbers.

Source: this report — 01 Known issues.

Head/turbo repair if outside CSP11 (owner/mechanic reports)several thousand
Same-engine head-crack repair (mechanic video, another Mazda)$7,614.63
If CSP11 window applies$0 (covered)
Why there’s no single “cost to own” number: sites that promise one are guessing at your insurance quote, your annual miles, and your luck. These are the numbers we can actually source — and each one carries its receipt.

Shopping this year?

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Have a specific one in your sights?

The VIN is on the listing. We’ll check this exact car — build, open recalls, and whether the “completed” repairs stayed fixed.

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Before you buy

Print this
  1. 01Inspect for coolant residue at the back of the engine block and a coolant smell — the cracked cylinder head (which on 2018s can reach the turbo and manifold) is this year's defining, expensive risk.
  2. 02Confirm any head/turbo replacement history and where the car sits in the CSP11 window (10yr/120k coolant-leak extension).
  3. 03Run the VIN against recall 19V403 (wiring harness / passenger airbag) and confirm it is completed — this one is specific to the 2018 CX-9.
  4. 04Run the VIN against recall 21V875 (low-pressure fuel pump) and confirm completed.
  5. 05Test the front brakes for warping and the automatic Smart Brake Support for false activation.
  6. 06Get all engine, cooling, and electrical repair history in writing.

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