IsItAGoodCar
Reliability Guide

Common Problems with the
2018 BMW i8 (I12)

The 2018 update brought the Roadster, a larger 11.6kWh battery and a 143PS motor. Electric range rose to about 34 miles, and the Roadster's two-seat roof mechanism replaced the rear seats.

What changed for 2018

  • •i8 Roadster launched in May 2018 with an electric two-piece folding roof
  • •Battery grows from 7.1kWh to 11.6kWh; electric motor rises to 143PS
  • •Combined output up to 374PS and official EV range up to 34 miles
  • •Coupé and Roadster both continue to the end of production in June 2020

Common MOT watch-outs

  • !Roof seals and drains on the Roadster leaking into the cabin
  • !Air conditioning failure, which also cools the high-voltage battery
  • !Tyre sidewall damage on the narrow 20-inch eco tyres
3
Known Issues
0
Serious
3
Moderate
0
Minor

All Known Issues

Door Strut Failure

ModerateBodywork & Rust

The lightweight carbon-fibre and aluminium dihedral butterfly doors rely on high-pressure gas damper struts hidden within the front wings. Over time, gas pressure escapes, causing the doors to drop unexpectedly or feel excessively heavy to lift.

Est. Repair Cost: £200–£400
Warning Signs:

Door drops shut or fails to stay locked at its highest open detent, Noticeably heavy effort required to lift door upwards, Creaking or groaning sound from wing strut cavity during door movement

What to Inspect:
  • Open both doors on level ground and confirm they remain fully upright without sagging
  • Check gas struts inside front wing aperture for oil misting or leakage
Verified by IsItAGoodCar Research Team

REx Fuel Pressure Sensor

ModerateFuel System

The petrol fuel tank is pressurized and sealed to prevent petrol vapour emissions during pure EV driving. The electronic fuel tank pressure relief sensor or tank vent solenoid valve can fail, causing the iDrive system to lock the fuel filler flap closed.

Est. Repair Cost: £300–£600
Warning Signs:

"Preparing for refuelling: please wait" message hangs continuously on dash, Fuel filler flap remains locked and will not pop open at petrol stations, Check engine warning light with EVAP fuel tank pressure sensor fault codes

What to Inspect:
  • Press fuel flap release button next to driver footwell and verify flap pops open within 5 seconds
  • Check boot emergency pull cord release mechanism for fuel flap
Verified by IsItAGoodCar Research Team

Steering Rack Knock

ModerateSteering

The lightweight electromechanical steering rack mounted to the front carbon-aluminium subframe develops internal clearance play between the steering rack bar and thrust piece, producing hollow metallic knocking over minor road imperfections.

Est. Repair Cost: £1,000–£2,000
Warning Signs:

Rattling or clunking feedback felt through steering wheel over cobbles and low-speed road ruts, Vague or loose on-centre steering response, Metallic knocking when rocking steering wheel side to side with engine off

What to Inspect:
  • Test drive over speed bumps and coarse asphalt listening for front-end hollow knocking
  • Inspect front steering tie rods and check if revised steering rack thrust piece bush has been fitted
Verified by IsItAGoodCar Research Team

Buying Tips for 2018 BMW i8 (I12)

  • On a Roadster, cycle the roof and check the boot and rear bulkhead for damp
  • Test the air conditioning for at least ten minutes and check for cold air
  • Scan for high-voltage and battery management fault codes
2015–20172019–2020
Check a 2018 BMW i8 (I12) by Registration