Mazda Miata NA (1990-97) and NB (1999-2005) buyer's checklist: rust, leaks, short-nose crank and recalls

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What should I check before buying an NA or NB Mazda Miata?

Short answer: It depends on the year. Run the VIN for open recalls first. On any NA or NB, look for rust in the rockers and floors (and the front side members on an NB) and check the soft-top drains. On a 1990 or early-1991 1.6, check for crank pulley wobble (the short-nose crank). On an NA, look for oil at the CAS O-ring; on a 1999-2000 NB, listen for a thrust-bearing rattle and check for coil-pack misfires.

Guide · 25 sources · Facts as of 2026-10-29

The checklist at a glance

Facts as of 2026-10-29. Each row summarizes a known-problem entry linked further down this page; the confidence tier of each entry is shown there. NA means the 1990-1997 car and NB the 1999-2005 car (US model years).

AreaLook or listen forWhich cars
Open recalls1991 ABS return lines, 1995 airbag sensor, Mazda accessory hardtop hoist; 1999 injector wiring and fuel filler valve; fog light bulb holderNA: 1991 with ABS, 1995, 1990-93 hoist. NB: 1999; 2001-03 with fog lights
Rust and drainsWet or smelly carpet; rusty rockers ahead of the rear wheel arches; rotten floors; NB front side membersNA and NB, especially East Coast NBs
Soft-top leaksWater behind the seats or in the footwells; blocked drains; cracked rain rail; drips at the side windowsNA and NB soft tops
Short-nose crankCrank pulley wobble; who did the last timing beltNA 1.6, 1990 and early 1991
Oil leaksNA: CAS O-ring and valve cover gasket, plus the heater hose under the CAS. NB: valve cover gasket, rear cam plug, front sealsNA and NB
Ignition and sensorsMisfires, hesitation or stalling (coil packs); stuttering or cutting out (crank and cam sensors)NB, coil packs on 1999-2000
Clutch and thrust bearingRattle with the clutch pedal down or when revving; shudder on engagementNB: rattle 1999-2000, chatter 2001-02
CoolingSeeping radiator end tanks; cracked reservoir or hoses; leaking front coolant elbowNA and NB; elbow on 1999-2000 NB
Rear differentialOpen, viscous, Torsen or Tochigi Fuji unit, and the 6-inch rear on early carsNA 1990-93 6-inch; Torsen optional from 1994; NB from 2003 Tochigi Fuji

1. Recalls: run the VIN first

NHTSA lists three NA recalls: about 300 1991 cars with ABS whose front brake return line was connected to a rear return, so front braking could be lost while the ABS works (91V-079); a 1995 airbag sensing unit that could read a sharp underbody hit as a crash (00V-004); and the buckles on Mazda's accessory hoist for storing the 1990-93 hardtop, which concerns the hoist, not the car (92V-159).

On the NB: on some 1999 cars the fuel injector harness can wear through against the intake manifold and stall the engine (98V-066); on 1999 cars the fuel filler non-return valve can stick (00V-032); and on 2001-03 cars with fog lights the bulb holder can come loose (03V-206). NHTSA lists no Takata airbag campaign for 1990-2005 Miatas. Coverage is by VIN, and most of these campaigns are decades old and likely done, but an open one is still free at a dealer.

2. Rust, drains and soft-top leaks

Hagerty says the NA's body drains plug up quickly and let water back up inside, which shows up as smelly or wet carpet, rusty rockers (notably just ahead of the rear wheel arches) and, at worst, blown-out floors. On the NB, Road & Track says to check East Coast cars for rust, and a forum owner reports the double-skin front side members rusting badly. Lift the carpet, look under the car, and walk away from structural rust unless the price allows a body shop.

Both generations drain the soft top the same way: water collects in a rain rail and leaves through a tube on each side, in the corner between the seatbelt tower and the body, under a carpet flap. Check both drains with water. On older cars the plastic rain rail can crack and leak onto the parcel shelf, and drips at the front corners usually come from shifted side-window weatherstrips or latches that no longer pull the top down tight. Owners warn that moldy carpet usually means rusting metal underneath.

3. Engine: short-nose crank, oil leaks and timing belt

Short-nose crank (1990 and early-1991 1.6): Hagerty says about 1% of these cars were affected: if the crank pulley key is reassembled badly during a timing-belt job, the pulley bolt can fail, which can end in a new crankshaft; Mazda changed the crank nose partway through 1991. When buying, look for crank pulley wobble, and have the timing belt done by someone who knows the early engine.

Oil leaks are normal on old Miatas but easy to trace. On an NA, the cam angle sensor (CAS) at the back of the valve cover seals with an O-ring that hardens and leaks, and the valve cover gasket is the other usual source. Oil from the CAS can drip onto the heater hose below and rot it, so check that hose. On an NB there is no CAS O-ring there: Mazda Motorsports' leak checklist names the valve cover gasket, the round cam plug at the back of the head, the cam and front crank seals and the rear main, and warns that oil running down the back of the engine is easily mistaken for a rear main leak. Owners disagree on how often the NB cam plug leaks.

Timing belt and plugs: Miata.net's used-car checklist tells buyers to ask for timing-belt and spark-plug records. Ask for receipts, or budget for the service at Mazda's interval.

4. NB ignition, sensors and idle

A forum problem list and a year-by-year page both say the 1999-2000 (NB1) ignition coil packs wear out, causing misfires, hesitation or stalling, and the year-by-year page says failing coils can damage the catalytic converter. A forum poster notes the NB2 uses a different ignition system without this issue. Replace coils, wires and plugs as a set.

The same two sources name the crankshaft position sensor, and cam angle sensor seal weaknesses, as a cause of stuttering or cutting out; sensor replacement is called an easy fix. The year-by-year page alone lists EGR codes 0401 and 0402 and idle dips on 1999-2000 cars, so treat that as a single report.

5. Cooling

Road & Track calls the NB cooling system relatively weak: the original plastic radiator end tanks go brittle, and bulky grille accessories or driving lights can block airflow. Look for seepage at the radiator and budget for an all-aluminum radiator.

A year-by-year problem page (which we could only read in excerpt) says reservoirs and hoses crack in hot, dry climates, and forum owners report the small pressed-in coolant elbow at the front of the 1999-2000 engine corroding and failing. On any car of this age, look for coolant crust at the hoses, reservoir and that elbow.

6. Drivetrain: thrust bearing, clutch and rear differential

Road & Track reports thrust-bearing failure in a few 1999-2000 NBs, also listed by a second source; most have probably been repaired, but listen for a rattle with the clutch pedal down or when revving. R&T also mentions clutch chatter (shudder on engagement) in 2001 and some 2002 cars, fixed only by a new clutch.

Know which rear end the car has. The 1990-93 1.6 uses a 6-inch differential that a drivetrain interchange guide calls not very strong; 1994 brought a larger 7-inch unit, and moving to it needs the matching housing, driveshaft and axles. Early NAs offered a viscous limited slip, a Torsen was optional from 1994, and R&T says NBs from 2003 use a Tochigi Fuji LSD instead of the Torsen. R&T says either limited slip beats an open differential, and Hagerty says any NA is one phone call away from having one.

Related known problems

FAQ

Which Miatas have the short-nose crank?

1990 and early-1991 cars with the 1.6. Mazda changed the crank nose partway through 1991. Hagerty says about 1% of those cars were affected, with failures linked to a badly reassembled crank pulley key after timing-belt work, so check the crank pulley for wobble.

Where do NA and NB Miatas rust?

On the NA, Hagerty names the rockers (just ahead of the rear wheel arches) and the floors, from body drains that clog. On the NB, check East Coast cars underneath, including the front side members. Clear the soft-top drains on either car.

What does a leaking CAS O-ring look like on an NA Miata?

Oil at the back of the valve cover, on the firewall or bellhousing, or a burning-oil smell. The oil can also rot the heater hose under the sensor. A new O-ring is a cheap DIY job; mark the CAS position first so timing stays put.

What recalls do NA and NB Miatas have?

NA: 1991 ABS return lines (about 300 cars), the 1995 airbag sensor and Mazda's 1990-93 hardtop hoist. NB: 1999 injector wiring and fuel filler valve, and 2001-03 fog light bulb holders. Check the VIN with NHTSA.

Keep exploring

Sources

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