Mazda MX-5 1.6 NB

Rust is the single biggest threat to any NB MX-5. The NB introduced double-layer steel construction for the front chassis rails (to meet updated crash regulations), and moisture gets trapped between the skins with no drainage path. Corrosion starts invisibly inside and only shows as paint bubbling or bulging when already advanced. The sills suffer similarly, with water from the soft top drains pooling if the drain tubes become blocked. Outer sill repair costs approximately €450-500 per side if caught early. If the inner sill and wheel arch need work, costs rise to €800-1,000+ per side. Front chassis rail repair runs approximately €400-600 for both sides at a specialist. A full structural restoration including sills, arches, and chassis rails can exceed €2,500. Always inspect with the wheels at full lock and remove any undertrays. Cars from southern Europe or those that have been professionally rust-proofed (such as with Dinitrol or Waxoyl treatment) are significantly better prospects.

At 20+ years old, most NB soft tops have degraded significantly. The vinyl becomes brittle and cracks at stress points, particularly around the rear window area and where the frame contacts the material when folded. The rain rail at the back can crack and allow water to pool in the rear deck and boot, which in turn causes rust in the body structure. A vinyl replacement top supplied and fitted costs approximately €500-700, while a mohair (fabric) top runs €700-1,200 fitted. The roof catches by the sun visors can also wear, preventing a proper seal. Most NBs available today will need a soft top replacement within the first few years of ownership if it has not been done recently.

The CAS (cam angle sensor) o-ring is the most common cause of oil leaks on the B6 engine. The factory rubber o-ring hardens over time and begins seeping oil, which drips onto the heater hose at the back of the engine. Left unchecked, the oil degrades the rubber heater hose, potentially causing a coolant leak as secondary damage. The o-ring itself costs under €5 and takes 20 minutes to replace. A Viton o-ring is recommended as a permanent fix. If the leak has been neglected, the heater hose and possibly the CAS sensor itself may also need replacing, bringing total costs to €100-400 at a garage. On some NB 1.6 cars, the CAS connector pins can also loosen from vibration, causing intermittent misfires or no-starts. Checking the connector is always the first diagnostic step.

The NB 1.6 uses a coil pack (wasted spark) ignition system rather than a distributor. The coil packs degrade over time due to heat cycling in the engine bay. Symptoms include engine misfires, rough idle, hesitation under load, and a check engine light with misfire codes. An OEM coil pack costs approximately €80-130, while aftermarket replacements are available from €40-70. Labour is minimal as the coils are accessible on top of the engine. Some owners report that very cheap aftermarket coils fail quickly. Quality branded replacements (NGK, Hitachi) are recommended. This is a common issue on high-mileage NB 1.6 models, typically appearing after 80,000-120,000 km.

The clutch slave cylinder is a known weak point on all MX-5s from 1990 to 2005. The internal seals deteriorate over time, causing the cylinder to leak fluid or fail to hold pressure. Symptoms include a soft or sinking clutch pedal, difficulty selecting gears, and eventually complete inability to disengage the clutch. The part costs approximately €30-60, and labour is around €100-150 at an independent garage. Many owners replace the clutch master cylinder at the same time for approximately €50-80 more in parts, as it is a similar age and likely to fail soon after. This is a straightforward repair that does not require gearbox removal.

At 20+ years old, the original radiator with its plastic top tank often develops cracks or seam leaks. Coolant expansion tanks also become brittle and crack. Overheating from a failed radiator can warp the aluminium cylinder head, turning a €200 radiator replacement into a €1,000+ head gasket repair. An aftermarket all-aluminium radiator costs approximately €100-200, with OEM-style replacements around €150-250. Fitting costs €100-200. All rubber coolant hoses should also be inspected and replaced preventively if they feel soft or swollen. Running correct coolant with corrosion inhibitor is essential to protect the aluminium head. Many NB owners consider an aluminium radiator upgrade a worthwhile preventive investment.

MX-5s that sit unused for extended periods or are stored without proper preparation are prone to sticking brake calipers. The rear calipers are particularly affected. Corroded pistons or seized slider pins cause uneven brake wear, pulling to one side, or in severe cases a locked wheel. A reconditioned caliper costs approximately €70-100 each, with new OEM calipers at approximately €120-150 each. Labour is around €50-100 per caliper. Regular driving and annual brake fluid changes help prevent this issue. Check for uneven pad wear and feel each wheel for excessive heat after a test drive.