1998 Mazda MX-5 Miata Problems: 6 Known Issues

On the 1990-1999 Mazda MX-5 Miata, nA and NB Miatas are prone to structural rust in two well-known areas: the rear ends of the rocker panels (sills) and the front frame rails behind the front wheels. Road water enters through wheel-arch pinch welds and body seams and collects inside the double-layer sheet metal, rotting it from the inside out even when exterior paint looks fine. NB (1999+) frame rails are double-layer ('tinfoil sandwich') and rust worse than the single-layer NA rails. Salt-belt/winter cars are worst, but even garage-kept examples show rear-rocker rot. Because the rockers are structural on these unibody roadsters, advanced rot compromises chassis rigidity and safety.

On the 1990-2025 Mazda MX-5 Miata, miata soft tops deteriorate over time from UV exposure, flexing during operation, and age. Vinyl tops develop cracks and tears, cloth tops fade and shrink. The rear plastic window (NA) or glass window (NB/NC/ND) can delaminate from the top material, causing water leaks and reduced visibility. Expected soft top life is 7-10 years with proper care.

On the 1990-1999 Mazda MX-5 Miata, nA and most early NB tops use a flexible plastic (vinyl) rear window, on many NA tops joined to the top with a zipper so the window can be lowered. With UV exposure and age the plastic yellows, hazes to near-opaque, and cracks (often starting at corners or the zipper seam); the zipper stitching tears out where the window meets the top. This is a near-universal age issue on unrestored cars and badly hurts rear visibility. A glass rear window with defroster was optional/standard on some later NB tops and does not haze, but zipper-window NA tops are the common case in this era.

On the 1990-2015 Mazda MX-5 Miata, all generations of Miata (NA through NC) are prone to rear main seal leaks as the engine ages. Oil seeps from the crankshaft rear seal, dripping onto the clutch housing and eventually contaminating the clutch disc. High mileage engines and infrequent oil changes accelerate seal deterioration. This is a labor-intensive repair as the transmission must be removed.

On the 1994-2000 Mazda MX-5 Miata, the 1994-2000 1.8L BP engines use a wasted-spark coil pack with an integrated igniter transistor. The early version (identified by the 4-pin input connector, later revised to 3-pin) is notorious for internal igniter/solder-joint failure, especially if the ignition is left in the ON position with the engine not running - the igniter transistor overheats and either burns out or melts its own solder connections. The result is a dead cylinder pair, a persistent misfire, and unburned fuel dumped into the catalytic converter.

On the 1990-1999 Mazda MX-5 Miata, both the 1.6L B6 and 1.8L BP are belt-driven and Mazda specifies timing-belt replacement at 60,000 miles. On 25-35 year-old cars, belts frequently fail on age/dry-rot rather than mileage. The engines are non-interference, so a snapped belt will not bend valves, but it will strand the car. The water pump is driven behind the timing belt and commonly weeps or fails in the same 70k-170k window, so it is standard practice to replace the pump, tensioner, and seals while the belt is off since ~90% of the labor overlaps.