Water in the footwell is one of the most common NC MX-5 (and JDM NCEC Roadster) problems. Left alone it rots the carpet, rusts the floor and can get into the electrics, so it's worth fixing early. The good news: the usual causes are cheap to fix.
Where's the water coming from?
1. Passenger footwell, behind the glovebox: scuttle grommets
This is the leak owners report most. At each end of the plastic cowl (scuttle) panel under the windscreen wipers there's a screw that goes into a threaded plastic grommet, sealed by a thin foam gasket. Over time the foam perishes and water runs down a brace behind the glovebox and into the footwell, sometimes onto the fuse box.
Signs: wet carpet on the passenger side after rain or a car wash, rust under the glovebox, worse when the car is parked facing uphill.
2. Behind the seats: blocked soft-top drains
The soft top has drains in the tray behind the seats that run down to exit near the rear wheels. Leaves and dirt block them, the tray fills, and water overflows into the cabin. Mazda issued a service bulletin (TSB 09-046/10) for this on 2006–09 soft-top cars, adding filters and updated drain valves.
Signs: water behind the seats or in both footwells, water sitting in the drain tray when you lower the roof.
3. Front of the roof (early 2006 cars)
Some early 2006 cars leaked at the front of the soft top past the header weatherstrip. Mazda's fix was a foam pad, part number NEY1-R1-433.
How to fix it
Scuttle grommets
- Pop the oval caps at each end of the cowl panel and undo the screws.
- Lift the cowl panel enough to reach the grommets.
- Replace the grommets, or clean them and bed them in a little silicone underneath (not just around the edge).
- Refit and test with a hose.
Soft-top drains
- Lower the roof partway so you can reach the drain holes in the tray.
- Push a flexible drain brush (or a trombone cleaner) down from the top and pull it out underneath. Don't pull it back up, as this can knock the one-way flap out of place.
- Pour water into the tray and check it comes out under the car near the rear wheels.
- If the valves or filters are damaged, replace them with the updated genuine parts below.
Retractable hardtop (RHT) cars have drain grilles just above the door shut line instead. Open the roof until the rear window starts to retract, remove the mesh grille and brush through from top to bottom.
Genuine Mazda parts (from Mazda's service bulletins)
| Part | Mazda part number | Qty |
|---|---|---|
| Drain filter, RH | NEY1-R1-782 | 1 |
| Drain filter, LH | NEY1-R1-792 | 1 |
| Foam drain cover filter | NH18-R1-782 | 2 |
| Drain valves (upper and lower) | NE51-R1-784E and NE51-R1-789E | 2 of each |
| Roof front foam pad (early 2006 cars) | NEY1-R1-433 | As needed |
Parts and fitment vary by build date and roof type, so send us your chassis number to confirm before ordering. We can source genuine Mazda parts in Japan through our import service, or check our JDM parts range for ready-made kits.
While you're in there
If your NC 6-speed has a vague shift, the same genuine-parts approach works: see our NC sloppy shifter fix and the NC 6-speed shifter repair kit.
FAQ
Is this the same on the ND?
No, the ND uses a different body and drain layout.
How do I dry the carpet?
Fix the leak first, then lift the carpet and dry the underlay properly. A wet underlay holds water for weeks and causes rust and smells.
Do I need a mechanic?
No. Both jobs are DIY with basic tools, a trim tool and a drain brush.