Mazda MX-5 1.8 NB
1998-2005Last updated: March 2026
1998-2005 · 1.8 BP (140-146 hp) 4-cylinder naturally aspirated petrol
The second-generation MX-5 refined the original's formula with a stiffer chassis, more power, and slightly better weather protection. The 1.8 BP engine is mechanically simple and long-lived, easily exceeding 300,000 km with regular oil changes and timing belt replacements. The NB2 facelift (2001-2005) added variable valve timing for 146 hp. Today, the biggest threat to any NB is not the engine but rust, particularly in the sills and front chassis rails.
Robust non-interference engine
Cheap parts, huge community support
Rust in sills and chassis rails
Soft top degrades with age and UV
Buy if: You want an affordable, engaging roadster and can find one with solid sills, clean chassis rails, and a documented timing belt history.
Avoid if: You live in a salt-heavy climate and the car has not been rust-proofed, or you cannot inspect the underside thoroughly before purchase.
Expected Annual Maintenance Costs
Known Issues most common first
Moisture trapped between double-skinned steel panels causes hidden rot from the inside out · more· less
Rust is the single biggest threat to any NB MX-5. Mazda used a double-layer steel construction for the sills and front chassis rails, and moisture gets trapped between the layers with no drainage. Corrosion starts invisibly inside and only shows as paint bubbling or bulging when it is already advanced. Sill repair costs approximately €450-500 per side if caught early (outer skin only). 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. Inspect carefully with the wheels at full lock and remove any undertrays. Cars from southern Europe or those that have been professionally rust-proofed are significantly better prospects.
Vinyl or fabric roof degrades with age and UV, leading to tears, leaks, and poor sealing · more· less
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. 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 cam angle sensor o-ring hardens and leaks oil down the back of the engine · more· less
The CAS (cam angle sensor) o-ring is the number one cause of oil leaks on the BP engine. The factory rubber o-ring hardens over time and begins seeping oil. On the 1.8, leaked oil drips onto the heater hose at the back of the engine, eventually degrading the hose. The o-ring itself costs under €5 and takes 20 minutes to replace, but the consequential damage (ruined heater hose, oil on exhaust) can make it seem worse than it is. A Viton o-ring is recommended as a permanent fix. If the leak has been left untreated, the heater hose and possibly the CAS sensor itself may need replacing, bringing total costs to €100-400 at a garage. Camshaft seals can also weep oil and cost approximately €200-350 to replace including labour.
Internal seals deteriorate, causing loss of clutch hydraulic pressure and inability to shift · more· less
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.
Coil-on-plug ignition coils fail causing misfires, rough running, and loss of power · more· less
The NB2 facelift models (2001-2005) use a coil-on-plug ignition system that is prone to failure. The coil packs degrade over time due to heat cycling. Symptoms include engine misfires, rough idle, and a check engine light with misfire codes. An OEM coil pack costs approximately €100-130, while aftermarket replacements are available from €50-70. Labour is minimal as the coils are easily accessible. Some owners report that cheap aftermarket coils fail quickly and recommend sticking with OEM Mazda or quality branded parts. Pre-facelift NB1 models (1998-2000) use a distributor-based system and do not have this issue.
Original plastic-topped radiator cracks with age, and coolant hoses deteriorate causing leaks · more· less
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.
Caliper pistons and slider pins seize from corrosion, especially on infrequently driven cars · more· less
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. Inspect brake discs for scoring and check for uneven pad wear during any viewing.
Mechanically robust, but rust is the real enemy
The BP 1.8 engine is one of the most durable four-cylinder engines Mazda ever produced. It uses a non-interference design, so even a snapped timing belt will not destroy the engine. With regular oil changes and timing belt replacements every 90,000 km, the engine routinely reaches 300,000 km and beyond. The gearbox is equally tough. The real threat is structural corrosion in the sills and chassis rails, which can make a car uneconomical to repair. Always prioritise body condition over mileage when shopping for an NB.
Pre-Purchase Inspection Checklist
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Service history
Verify regular oil changes (every 10,000-15,000 km) and timing belt replacement history. Look for stamped service book or receipts.
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Tires
Check tread depth, age (date codes), and uneven wear patterns. Standard size: 195/50R15 or 205/45R16.
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Cold start
Start the engine completely cold. Listen for tappet noise and check that idle settles smoothly within 30 seconds.
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Test drive
Drive for at least 20 minutes including varied speeds. Check gearbox shifts cleanly through all five or six gears.
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Inspect sills and chassis rails for rust
Remove undertrays and inspect with a torch. Check inner sills from wheel arches with wheels at full lock. Bubbling paint or bulging panels indicate advanced hidden corrosion. This is the most important check on any NB.
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Check for oil leaks at back of engine
Look at the rear of the cylinder head for oil residue dripping from the CAS o-ring or camshaft seals. Check the heater hose below for oil damage.
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Verify timing belt replacement date
The timing belt should be replaced every 90,000 km or 5 years, whichever comes first. If no evidence of replacement exists, budget for immediate replacement.
Recalls and Technical Service Bulletins
Front fog light socket holder detachment due to thermal expansion (selected NB models)
Verify completed
Takata airbag inflator (if applicable to production date and market)
Verify completed
The NB MX-5 had very few recalls. Contact a Mazda dealer with the VIN to verify whether any applicable recalls have been completed, including the Takata airbag recall which affects many vehicles from this era.
Warranty Status
Factory warranty (3 years / 100,000 km)
Expired on all NB models
Rust perforation warranty
Expired (originally 6 years)
Extended warranty
Not available for vehicles this age
All Mazda MX-5 NB models are well outside their original factory warranty. No extended warranty programs are available from Mazda for vehicles of this age. Third-party warranty providers may offer limited coverage but typically exclude pre-existing conditions and corrosion.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.