Mazda Roadster NB (1998 to 2005): buying guide, problems and NZ numbers
The Mazda Roadster NB was built from 1998 to 2005 as a convertible or coupe, with a manual or automatic gearbox, rear wheel drive and petrol power. Chassis codes: NB6C and NB8C. Redline has a curated guide to its 7 most reported weak points, from owner club and specialist sources.
Key facts
- Years
- 1998 to 2005
- Chassis codes
- NB6C, NB8C
- Body types
- Convertible, Coupe
- Gearboxes
- Manual, Automatic
- Drive
- RWD (rear wheel drive)
- Fuel
- Petrol
On NZ roads
Counting every one on the NZ register. The first look can take up to 15 seconds.
Known weak points
Curated by Redline from owner club and specialist sources Commonly reported by owners and specialists for the Mazda MX-5 NB (1998 to 2005). Not every car has these; check this one.
Front chassis rails
The front chassis legs are double skinned and can rot from the inside. Specialists describe rot here as often terminal.
- Where to look
- Under the front of the car with the undertray off: the two chassis legs running back from the front crossmember, and where they meet the floor behind the front wheels
- How to test
- Touch and press the chassis legs with a torch in hand. If metal flakes off or there is fresh underseal or patching, walk away or get a hoist inspection first.
- Cost if it needs fixing
- High cost structural welding; can write the car off
Sources: insurance.goodwood.com (opens in a new tab), sps-motorsportshop.com (opens in a new tab)
Rear sills and sill to arch joins
Rust in the rear sills and where they join the rear arches is widely reported, and many cars already have patch repairs.
- Where to look
- The rear end of each sill and the join with the rear wheel arch, inside and out
- How to test
- Use a magnet and probe gently to judge any repair. A patch welded over rusty metal keeps rusting underneath.
- Cost if it needs fixing
- High cost new sill sections and paint
Sources: insurance.goodwood.com (opens in a new tab), sps-motorsportshop.com (opens in a new tab)
Rear wheel arches
Rear arches rust from the inside out, so visible bubbling is usually only part of it. Blocked drains make it worse.
- Where to look
- Inside the lip of each rear wheel arch
- How to test
- Run a finger inside the arch lip and look with a torch for flaking metal or filler.
- Cost if it needs fixing
- Medium cost panel repair and paint
Sources: insurance.goodwood.com (opens in a new tab), sps-motorsportshop.com (opens in a new tab)
Hood drains and roof leaks
Leaking roofs and blocked drain holes are commonly reported. The fabric also tends to tear at the fold above the side windows.
- Where to look
- The drain holes behind the seats, the carpets under the seats, and the hood fabric above each side window
- How to test
- Lift the carpet and feel for damp. Raise and lower the hood by hand during the viewing and check it closes tight. The front latches should not open without pressing the safety button.
- Cost if it needs fixing
- Medium cost a new hood, or floor repairs if water has sat for years
Sources: insurance.goodwood.com (opens in a new tab), sps-motorsportshop.com (opens in a new tab)
Rear main seal and sump gasket
Oil leaks at the gearbox bellhousing are reported, and in most cases come from the rear crankshaft seal or the sump gasket.
- Where to look
- The join between the engine and gearbox, and the sump edge, from underneath
- How to test
- Look for wet oil and caked dirt where the engine meets the gearbox and around the sump.
- Cost if it needs fixing
- Medium cost the gearbox has to come off for the rear main seal
Radiator and cooling system
Cooling system neglect and radiator wear are commonly reported. A radiator whose plastic has faded from black to light grey is near the end.
- Where to look
- The plastic end tanks of the radiator and the coolant expansion tank
- How to test
- With the engine cold, look at the radiator plastic colour and for crust at the seams. Check under the oil filler cap for mayonnaise.
- Cost if it needs fixing
- Low cost aftermarket radiators are cheap
Sources: insurance.goodwood.com (opens in a new tab), sps-motorsportshop.com (opens in a new tab)
Suspension bushes and rear calipers
Tired bushes, worn dampers and seized brake calipers are listed as common problems.
- Where to look
- The wishbone bushes at each corner and the rear calipers
- How to test
- Look for cracked bushes. On the test drive listen for knocks and check the car brakes in a straight line.
- Cost if it needs fixing
- Medium cost bushes are fiddly to replace and need an alignment after
Sources: insurance.goodwood.com (opens in a new tab), sps-motorsportshop.com (opens in a new tab)
General guidance from owner and specialist sources. Check the specific car with an independent inspection. Researched 1 November 2026.
What the cost bands mean
- Low: a small job. Typically a few hundred dollars or less at an NZ workshop, often a DIY fix.
- Medium: a proper workshop job. Typically several hundred to a couple of thousand dollars.
- High: a major job. Typically several thousand dollars or more, enough to change what the car is worth.
Service items
- Cambelt and water pump: every 5 years if there is no record of a recent change (Goodwood checklist); about 100,000 km on the UK schedule. The BP is driven by a belt; budget for it at the first service. (insurance.goodwood.com (opens in a new tab))
- Hood drains: clear every year. Prevents sill and floor rust. (insurance.goodwood.com (opens in a new tab))
- Wheel alignment: after any bush or suspension work. The geometry is adjustable and sets the handling. (sps-motorsportshop.com (opens in a new tab))
Questions to ask the seller
- Has the car been on a hoist recently, and has anyone looked at the front chassis legs?
- Has any rust repair been done on the sills or arches, and are there photos from before the underseal?
- When were the cambelt and water pump last done, and at what km?
- Is it a 5 speed or 6 speed, and does it have the LSD?
- Has the hood been replaced, and has the carpet ever been wet?
New Zealand notes
- Many NZ cars are Japanese import Roadsters. Compare the odometer on the export certificate with the dash.
- The NB hood is a manual soft top with a glass rear window on most cars. There is no hood motor to check.
An NB suits a driver who wants a light, simple roadster and is ready to check the structure properly before buying.
US recalls
Looking up US recall data.
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