Daihatsu Rocky: Lower Body Sill and Wheel Arch Seam Corrosion

The A200S Rocky's lower sill pinch welds and the rear wheel arch lip seam are factory-seamed rather than continuously welded, creating moisture traps where road film accumulates. Australia and coastal AU environments accelerate corrosion at these joints, with rust propagating under factory underbody coating. First generation Rocky (2019-2021) units with thin anti-corrosion wax application are disproportionately affected. Documented roadworthy inspection refusal records and owner community photographic evidence. Corrosion in advanced form compromises the structural sill which is a safety-critical load path in a side-impact.

• Bubbling or lifting paint along the lower door sill, often starting at the front-door step edge
• Visible rust or brown staining at the rear wheel arch seam above the tyre
• Soft or perforated metal detected by probing at pinch weld seams
• Roadworthy refusal citing corrosion in structural sill area

1. 1

   Use a magnet along the lower sill to detect filler.

2. 2

   Lift floor mats and inspect sill inner faces for rust staining.

3. 3

   Probe the rear wheel arch lip with a blunt pick for soft metal.

4. 4

   Inspect underneath with a torch at the pinch weld seam along the full length of both sills.

5. 5

   Check for bubbling in the factory underbody coating as an early indicator.

Parts involved: Body corrosion.

≈A$640 to ≈A$3,220 at independent workshop rates, shown as an approximate guide in Australian dollars. That is for this job on its own, not for the car.

An estimate, converted to Australian dollars, 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 the underbody or sills been treated with rust protection, and when was it last done?”
• “Has the car been used in a coastal environment or regularly driven on unsealed roads?”

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.