1990 Mazda Miata Has A Coolant Leak

Identifying the Causes of Coolant Leaks in Your 1990 Mazda Miata and How to Fix Them

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Reviewed by
Aisha
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 1990 Mazda Miata 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 1990 Mazda Miata 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.

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

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 are the steps to diagnose a coolant leak in a 1990 Mazda Miata?

To effectively diagnose a coolant leak in your 1990 Mazda Miata, begin with a thorough visual inspection of the vehicle. Look for any visible signs of coolant on the ground beneath the car, as this can provide immediate clues about the leak's location. Next, examine the radiator and hoses for any cracks, holes, or loose connections that could be contributing to the problem. If no obvious leaks are found, consider performing a pressure test on the cooling system, which can help identify leaks that are not visible to the naked eye. Additionally, inspect the water pump and heater core, as these components are common sources of leaks. Don’t forget to check the radiator cap to ensure it is sealing properly, as a faulty cap can also lead to coolant loss. Throughout this process, monitor the coolant levels in the reservoir; a consistent drop in levels can indicate a leak. If you are still unable to pinpoint the source of the leak after these steps, it may be wise to consult a mechanic for a professional diagnosis. By following this diagnostic approach, you can systematically identify and address coolant leaks in your Miata, ensuring your vehicle remains in optimal condition.

What are the common causes of a coolant leak in a 1990 Mazda Miata?

When dealing with coolant leaks in a 1990 Mazda Miata, it's essential to understand the common culprits that may be at play. One of the primary issues is worn-out hoses, which can crack and leak due to age and exposure to heat. Inspecting these hoses for any signs of wear is a crucial first step. Additionally, a faulty radiator can contribute significantly to coolant loss; corrosion or physical damage can create leaks that are often visible. The water pump, responsible for circulating coolant, can also develop leaks over time, so checking for any signs of moisture around this component is advisable. Another area to examine is the radiator cap; a cracked or improperly sealed cap can lead to coolant escaping under pressure. Furthermore, the heater core, which can become damaged, may also be a source of leaks, particularly if you notice a sweet smell inside the cabin or wet carpets. Lastly, ensure that hose clamps are secure and undamaged, as loose or broken clamps can prevent a proper seal, leading to leaks. By systematically checking these components, DIY enthusiasts can effectively identify and address coolant leaks, helping to maintain the health of their Miata's engine.

How urgent is it to address the coolant leak in a 1990 Mazda Miata to prevent potential engine damage and safety risks?

Addressing a coolant leak in your 1990 Mazda Miata is not just a matter of routine maintenance; it is an urgent necessity to safeguard your vehicle's engine and ensure your safety on the road. A coolant leak can lead to severe overheating, which may warp cylinder heads or blow head gaskets, resulting in costly repairs that could have been easily avoided. Moreover, the risk of a cracked engine block looms large if the issue is ignored, potentially leaving you stranded and facing significant repair bills. Beyond mechanical failures, a coolant leak poses immediate safety hazards. It can create slippery road conditions, increasing the likelihood of accidents, while inhaling coolant vapors can be detrimental to your health. Therefore, it is imperative to address any signs of a coolant leak promptly to protect both your vehicle's integrity and your well-being.

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Common Causes of Coolant Leaks in 1990 Mazda Miata