NB Miata
The second generation NB Miatas are generally considered more reliable to its predecessor, the NA Miata, Sadly ditching its beloved pop-up headlights, the NB Miata comes with more power, enhanced refinement, and improved safety features. To this date, the NB Miata still stands out as an affordable option for those who want the thrills of a classic roadster without breaking the bank. However, like all older cars, the NB Miata does have its fair share of common issues. Let’s dive into some of the most notable ones and how to fix them.
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One of the most well-known issues in early NB Miatas, specifically from the 1999-2000 model years, is premature thrust bearing failure. This problem occurred due to Mazda fitting the wrong part, leading to excessive wear on the crankshaft’s thrust bearing. Over time, this wear can lead to severe engine damage if not addressed.
The symptoms of thrust bearing failure typically present as a knocking or grinding noise when the clutch is depressed. If left unchecked, this issue can cause catastrophic engine failure. Most cars would show signs of failure around 40,000 miles, so if you’re buying an NB Miata with higher mileage, it’s likely that this problem has already been resolved. Always check for service records or ask the owner directly if the thrust bearing issue has been addressed. In the rare instance it hasn’t, the fix involves a complete engine rebuild or replacement, which is a costly but necessary repair.
The catalytic converter in an NB Miata can clog due to coil pack failure. When a coil pack malfunctions, it causes unburnt fuel to flow through the exhaust system, which eventually leads to clogging of the catalytic converter. Drivers will notice a significant loss of power, reduced fuel economy, and the dreaded check engine light, often showing a P0420 code indicating “catalyst system efficiency below threshold.” Cleaning the EGR valve is usually sufficient to restore proper function, though in some cases, a replacement may be necessary. Regular maintenance, such as periodically cleaning the EGR system, can help prevent future issues. If you notice your check engine light turning on intermittently, it’s worth looking into the EGR valve as a potential cause Once a catalytic converter is clogged, the only solution is replacement. Aftermarket converters may be more affordable than OEM parts, but they often don’t last as long. To prevent further clogging, make sure your coil packs are functioning correctly before replacing the catalytic converter.
The fuel pump in the NB Miata relies on gasoline in the tank to stay cool. If you frequently let your fuel level drop too low, the pump can overheat and burn out. This is an avoidable issue, but it still happens to many owners. Symptoms of a failing fuel pump include engine sputtering or stalling, especially during acceleration, and difficulty starting the car. In worst-case scenarios, the engine may not start at all if the pump completely fails. The solution is to replace the fuel pump, but this problem can be easily prevented by keeping the fuel level above one-quarter of a tank at all times. By doing so, you’ll avoid unnecessary wear on the fuel pump and extend its lifespan.
Coil pack failures are another common issue in NB Miatas, particularly affecting both NB1 (1999-2000) and NB2 (2001-2005) models. Coil packs are responsible for firing the spark plugs, and when they fail, the engine will start to misfire. Symptoms of a coil pack failure include a rough idle, hesitation during acceleration, and noticeable misfires, especially under heavy load. If this problem is ignored, it can lead to even more significant issues, such as a clogged catalytic converter, as unburnt fuel passes through the exhaust. The fix is relatively straightforward: replace the faulty coil packs with either OEM replacements or high-quality aftermarket options. It’s essential to address misfires early to avoid additional damage and keep your engine running smoothly.
A common sound heard by many NB Miata owners is a ticking noise coming from the valves, particularly if the car has missed its oil change intervals. While this sound can be concerning, in most cases, it isn’t something to worry about. The ticking is typically most noticeable at idle or when the engine is cold. Regular oil changes with high-quality oil can help reduce the noise and keep the engine running smoothly. In severe cases, a valve adjustment may be necessary, but this is rarely required for most owners. As long as you keep up with regular oil changes, your Miata’s valves should remain in good condition.
As the NB Miata ages, one of the more common maintenance issues you’ll encounter is a leaking valve cover gasket. This is a rubber seal that can become brittle over time, leading to oil leaks. Symptoms of a valve cover gasket leak include oil dripping from the top of the engine and the smell of burning oil. Fortunately, this is an easy and inexpensive fix. Replacing the valve cover gasket can be done in about 15 minutes with basic tools. It’s a simple DIY repair that many owners tackle themselves without needing professional help.
Clutch slave cylinder failure is a common issue in NB Miatas, often leading to problems with clutch engagement. A failing clutch slave cylinder will result in a soft or spongy clutch pedal, making it difficult to shift gears smoothly.
The good news is that replacing the clutch slave cylinder is a relatively straightforward task. After installation, you’ll need to bleed the clutch system to remove any air bubbles in the hydraulic line. It’s also a good idea to monitor the fluid levels in the clutch master cylinder regularly to avoid further issues. With proper maintenance, your clutch should remain in top working order.
The NB Miata’s power antenna is notorious for failing over time, especially if the car is exposed to harsh weather conditions. The motor may grind without moving the antenna, or the antenna may fail to extend or retract altogether. Many owners choose to replace the motor, but an easier solution is to install a fixed antenna. With modern audio systems, many drivers bypass the need for an antenna entirely by installing a Bluetooth stereo system. This eliminates the problem altogether while giving you the added benefit of wireless audio streaming.
Of course, the dreaded rust issue of the MX-5. Rust is one of the most significant concerns for NB Miata owners, especially in humid or coastal areas. The most vulnerable areas are the rocker panels, fender arches, and, less commonly, the front frame rails.
Rocker panel rust is particularly problematic because it can develop internally and go unnoticed until the damage is extensive. Fender arches also rust due to poor drainage. Fixing rust requires cutting out and replacing damaged panels, which can be expensive. The best solution is prevention—regularly inspect your Miata for signs of rust, especially around the rocker panels, and consider applying rust-proofing treatments. Additionally, ensure the convertible top’s drainage system is clear to avoid water buildup.
Over time, the convertible top on the NB Miata will naturally degrade due to exposure to sunlight, rain, and general wear and tear. Small tears or leaks can develop, and the top may become harder to operate. When this happens, it’s time to replace the soft top. Fortunately, replacement tops are widely available, and you can choose between the original vinyl material or upgrade to a more durable canvas top. Installing a new top can be done yourself or by a professional, and an upgraded material can provide better protection and longevity.
The NB Miata uses a traditional spring-and-shock suspension setup, which wears out over time. The springs are generally durable, but the shocks, bump stops, and shock mounts tend to degrade, leading to a bumpy ride. If you notice clunking sounds when driving over bumps or a generally rougher ride, it’s time to replace these components. Upgrading to aftermarket coilovers is a popular choice for Miata owners who want to improve handling and fine-tune the suspension for performance driving. Even replacing the stock components with new OEM parts can make a significant difference in ride quality.
As with any older car, regular maintenance is key to keeping your NB Miata running smoothly. Check hoses, belts, and gaskets for wear and replace them as needed. Make sure to replace the timing belt and water pump every 60,000-80,000 miles to avoid a major failure. Finally, changing the transmission and differential fluid at regular intervals will prolong the life of your Miata’s drivetrain.
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