Daihatsu Sirion: Rear Sill and Door Bottom Edge Corrosion

M100 and M300 Sirion bodies corrode predictably at the rear sill ends where road water is thrown by the rear tyres, and along the bottom edges of all four doors where the hemmed seam traps moisture. The rear quarter panel above the rear wheel arch also blisters. NZ-imported M300 units often show this rust pattern earlier than Australian-delivered vehicles owing to higher rainfall and coastal salt exposure. Rust in the door bottoms is largely cosmetic but untreated sill rot can spread to the structural floor pan.

• Paint bubbling along the bottom edges of doors
• Rust staining or perforation on the rear sill ends behind the rear wheels
• Blistering paint on the rear quarter panels above the wheel arch
• Water ingress on interior carpet near the sills

1. 1

   Run a finger along the bottom hem of each door — bubbling paint indicates trapped moisture and rust behind the hem.

2. 2

   Probe the rear sill ends firmly with a screwdriver tip.

3. 3

   Inspect the rear quarter panel from inside the boot for blistering.

4. 4

   If a workshop inspection is possible: Lift the rear carpet to check whether sill rot has spread to the floor.

Parts involved: Body corrosion.

$400 to $2,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has any rust treatment, panel repair or repainting been done?”
• “Has the vehicle been stored outside near the coast?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.