2020 Mazda CX-9 Has A Coolant Leak

Troubleshooting Coolant Leak Issues in Your 2020 Mazda CX-9: Causes and Repair Solutions

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Reviewed by
Devin Cabugcal
Written by RepairPal Car Genius
Updated January 14, 2025
0%
50% chance it's the
Loose Hose Connections
0%
25% chance it's the
Radiator
0%
25% chance it's the
Water Pump
The most common reasons a 2020 Mazda CX-9 has a coolant leak are loose hose connections, a broken radiator, or a failed water pump.
  • Loose Hose Connections: A loose hose connection can lead to vacuum leaks or fluid loss, resulting in poor engine performance or overheating.
  • Radiator: A damaged or clogged radiator can impede coolant flow, resulting in engine overheating and reduced cooling efficiency.
  • Water Pump: A failing water pump can lead to coolant leaks or overheating due to inadequate circulation of coolant in the engine.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a 2020 Mazda CX-9 has a coolant leak?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

When the head gasket begins to fail, the engine may have no symptoms at all. They only begin to occur when the leak has reached an engine oil passage, engine coolant passage or the engine cylinder.

When that happens, the engine may be very difficult to start, and run roughly when idling. There may be oil or coolant leaking, and the engine may begin to overheat, or at least run hot. At this point, there may be coolant in the engine oil pan — this will look creamy and lighter in color than the oil. Also, the radiator or engine coolant reservoir may have a gurgling sound, the presence engine oil, or smell of combustion. And the check engine light will come on.

The coolant being burned in the engine will produce white exhaust that smells sweet, like engine coolant. When the head gasket fails completely, the engine will overheat within minutes of starting, will stall and then won't restart.

A failing heater core may cause the car's interior to smell like engine coolant. The smell will become worse when the heater is turned on. The engine may also begin to run hotter until the vehicle is repaired.

The worst-case scenario is the engine overheating, which can cause extensive engine damage.

If the heater core is clogged, the air that blows when the heater is turned on will not be very hot.

Problems with the intake manifold gasket can create the following symptoms:

  • Illuminated check engine light
  • Erratic engine performance
  • Oil and coolant leaks
  • Poor gas mileage
  • Stalling

» LEARN MORE: Intake manifold gasket symptoms

A failing radiator can cause the engine to run hot or overheat. Most radiators are made of metal and plastic. The plastic parts can become brittle and crack over time, causing a leak of coolant (typically green or pink in color). All manufacturers have a recommended service interval for coolant renewal. As the coolant ages, the additives breakdown and being to form solid deposits. These deposits will build up in the passages of the cooling system and will eventually clog components, including the radiator. A leaking or clogged radiator must be replaced. Some automatic transmission cars will also have a transmission cooler integrated into the radiator. Lines going to and from the transmission circulate transmission fluid to help cool the transmission in heavy duty applications such as towing or off-roading. If this integrated cooler fails, it can allow transmission fluid and coolant to mix. This will causing shifting issues in addition to overheating.

A coolant leak may be noted from the hoses. Coolant hoses can be damaged by oil leaks, or age. This will lead to swelling or cracking, it is suggested to replace the hoses before they begin leaking to avoid potential overheating.

The bad thermostat can cause two different sets of problems, depending on whether it's stuck open or stuck closed.

A thermostat that is stuck open can cause the engine to run colder than normal and turn on the check engine light. It may also cause poor fuel mileage and the heater to blow cool air.

A thermostat that is stuck closed will cause the vehicle to overheat. If a new thermostat doesn't resolve engine temperature problems, the cooling system needs to be checked for other issues.

» LEARN MORE: Signs of a bad thermostat, and how to fix it

If a vehicle is overheating, a bad thermostat could be the problem, and a damaged thermostat housing is more likely to produce a coolant leak, either from a cracked or warped housing or a failed seal to the engine. The thermostat housing can be made of metal or plastic. And the housing can be a stand-alone part that is separate from the thermostat, or (on later model vehicles) can be integrated with the thermostat and replaced as a single unit.

The two most common signs of a bad pump are leaks and noises.

Leaking water pumps can result in damage to the drive and timing belts, and cause the engine to overheat. A failed water pump can be caused by other problems in the cooling system, such as a bad thermostat, radiator or head gasket.

What steps should I take to diagnose the coolant leak in my 2020 Mazda CX-9?

To effectively diagnose a coolant leak in your 2020 Mazda CX-9, start by visually inspecting the area beneath your vehicle for any puddles of coolant, as this can provide immediate clues about the leak's location. Next, examine the hoses and connections for any visible signs of wear, cracks, or loose fittings that could be contributing to the leak. If no obvious issues are found, consider performing a pressure test on the cooling system, which can help pinpoint leaks that are not easily visible. Pay special attention to the radiator, as corrosion or damage here is a common source of leaks. Additionally, inspect the water pump and heater core, as these components can also fail and lead to coolant loss. If you notice white smoke from the exhaust, this could indicate a more serious issue, such as coolant entering the engine. Finally, keep track of your coolant levels over time; a consistent drop may signal a leak that requires further investigation. By following this structured approach, you can efficiently diagnose and address coolant leaks in your vehicle.

What are the common causes of a coolant leak in a 2020 Mazda CX-9?

When dealing with coolant leaks in a 2020 Mazda CX-9, it's essential to understand the various components that may be at fault. One of the most frequent culprits is damaged hoses, which can develop cracks or wear over time, leading to leaks in the cooling system. Additionally, a faulty radiator, often characterized by corrosion or physical damage, can also contribute to coolant loss. The water pump, responsible for circulating coolant, may leak if it becomes worn or damaged, while a cracked radiator cap can allow coolant to escape from the system. Furthermore, loose or damaged clamps that secure the hoses can lead to leaks, as can a leaking heater core, which is another potential source of coolant loss. If you notice signs of a coolant leak, such as puddles under your vehicle or a drop in coolant levels, it's crucial to inspect these components promptly to prevent overheating and protect your engine from potential damage.

How urgent is it to address the coolant leak in a 2020 Mazda CX-9 to prevent potential engine damage?

Addressing a coolant leak in your 2020 Mazda CX-9 is not just a matter of routine maintenance; it is an urgent necessity to safeguard your engine's health. Coolant plays a vital role in regulating engine temperature, and any leak can lead to overheating, which poses a serious risk of catastrophic engine damage. If left unchecked, the consequences can escalate quickly, resulting in warped cylinder heads, blown head gaskets, or even a cracked engine block. Moreover, the damage can extend beyond the engine itself, affecting critical components like the water pump, radiator, and thermostat. Ignoring these symptoms can lead to complete engine failure, which not only incurs hefty repair costs but may also necessitate a full engine replacement. Therefore, it is imperative to address any signs of a coolant leak immediately to prevent costly repairs and ensure the longevity of your vehicle.

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