Galvanised Floor Crease and Structural Pull
A 2018 sedan has left-side impact damage. The left rocker panel is kinked at the midpoint, the floor pan has a 40 mm sharp crease under the rear seat, and bench measurements show the left front body mount is 8 mm rearward and the right rear body mount is 2 mm rearward. The OEM tolerance is ±3 mm. The insurer has authorised 6.0 hours to pull the structure. A technician proposes heating the floor pan to 400°C to relieve the crease, then pulling with a chain and porta-power. The vehicle has deployed side curtain airbags, the battery is disconnected, and the floor pan is galvanised on both sides. The workshop's bench has a pulling tower and electronic measuring system, but the left sill clamp is missing a pin.
1. Evaluate the technician's proposal to heat the floor pan to 400°C and pull with a chain and porta-power. State what you would authorise instead.
Read the worked answer
I would reject the proposal.
Heat
- The floor pan is galvanised. Heating to 400°C damages the zinc coating and produces zinc oxide fume, which is a health hazard without proper extraction. It also changes the properties of the steel and can create a corrosion site that is difficult to restore.
- A sharp 40 mm crease is a stress concentration. Heating and pulling it can tear the panel or leave a weakened area that is not visible after underseal.
Pulling method
- A chain and porta-power is not a controlled pull. It gives poor force direction and no gradual release, so the technician cannot measure spring-back accurately.
- The missing sill clamp pin means the vehicle is not restrained at the specified point. Pulling could move the vehicle on the bench and give false measurements.
What I would authorise
- Fit the correct sill clamp and pin first.
- Mount the vehicle on the bench at the OEM support points and measure all control points.
- Use the pulling tower with a controlled, multi-point pull and measure in stages. If the crease cannot be removed within OEM tolerances, replace the floor section per the OEM procedure.
- Address the deployed side curtain airbags and pretensioners as part of the repair, including diagnostics and replacement.
- Submit a supplement if the authorised 6.0 hours does not cover the correct method.
2. Set out the pull sequence and measurement checkpoints, including what you would do if the front body mount returns to within 2 mm but the door aperture is still 5 mm out.
Read the worked answer
Pull sequence
- Fit the correct clamps and pins. Mount the vehicle at the OEM support points.
- Record baseline measurements at all control points, including the front and rear body mounts, aperture diagonals, sill and floor reference points.
- Apply a low controlled pull in the direction of the impact. Pull in small increments rather than one long pull.
- Release the tension, re-measure the control points and check for spring-back and new kinks.
- Repeat until the primary dimensions are within tolerance or until the panel shows signs of tearing or over-stretch.
- Check door fit, aperture gaps and hinge condition before and after each pull.
If the front mount is within 2 mm but the aperture is 5 mm out
- Do not chase the aperture by pulling harder on the same anchor. The structure may be storing energy or there may be damage in the A-pillar, hinge pillar or sill that is not being addressed.
- Re-check the datum and clamp positions. Confirm the measurement is not being affected by a loose clamp or suspension movement.
- Inspect the aperture and hinge areas for kinks, cracks and weld damage. Measure the diagonals and compare both sides.
- If the damage is in the aperture rather than the front mount, a different pull direction or a section repair may be needed. I would stop, document the readings and submit a supplement rather than force the structure.
3. What final checks and records would you complete before releasing this vehicle, given the airbag deployment and structural repair?
Read the worked answer
Final checks
- Re-measure all control points after the vehicle is off the pulling rig and suspension is loaded.
- Check door, bonnet and boot alignment, aperture gaps and water sealing.
- Inspect all welds, seams and repaired areas for cracks, distortion or missing corrosion protection. Restore primer, seam sealer, cavity wax and underseal.
- Replace deployed side curtain airbags and pretensioners as specified. Carry out a diagnostic scan, clear codes only after the repair is verified, and confirm no airbag faults remain.
- Check the battery, seat belts, occupant sensors and related wiring. Carry out a road test if the OEM procedure requires it.
Records
- Before, during and after measurement printouts.
- Photographs of the damage, pull setup, welds and corrosion protection.
- The OEM procedure or technical note used for the pull and section repair.
- Supplementary authorisation for any additional hours or parts.
- Airbag diagnostic scan results and parts invoices.
- Final quality-control sign-off and customer handover notes.
I would not release the vehicle on the insurer's original 6.0 hours if the correct repair required more. The file must show that the structure and supplementary restraint system were restored to a safe condition.