Hyundai Sonata

The Theta II 2.4 GDi is also covered by the worldwide Hyundai recall. 3.9 million vehicles affected. Warranty extended to 15 years / 150,000 miles for connecting rod bearings.

Symptoms: Knocking from the engine, oil pressure drop, sudden engine stall, fire risk from metal swarf.

The G4KJ 2.4L GDi is part of the Hyundai Theta-II recall series. Metal swarf from crankshaft machining blocks oil galleries and causes connecting rod bearing failures. Affected models include various Sonata, Santa Fe and ix35 model years.

Symptoms: Metallic knocking, engine warning, oil pressure drop, engine stall

Like all Theta-II engines, the G4KJ is prone to timing chain stretch when oil changes are neglected. A jumped chain contacts valves against pistons. Workshop repair involves a complete chain kit and often cylinder head reconditioning.

Symptoms: Chain rattle on cold start, power drop, engine misfires

Like all GDi direct-injection engines, the G4KJ accumulates deposits on the intake valves. Regular engine flush or walnut-blasting every 60,000–80,000 km recommended.

Symptoms: Rough idle, acceleration stumble, P030x misfire codes, power loss.

The G4KJ tends toward measurably elevated oil consumption above 100,000 miles due to piston ring and seal wear. The class-action lawsuit against Hyundai for excessive oil consumption explicitly included the Theta engine.

Symptoms: Rising oil consumption to 0.5–1 L/1,000 km, oil pressure warning, blue smoke

The Mitsubishi F4A42 automatic transmission in the Sonata NF is known for reverse gear failures. Clutch packs and solenoids wear, requiring a full transmission overhaul. Cost: 2,500–3,000 euros.

Electrical short circuit in the ABS/VDC control unit can cause an engine compartment fire even when the vehicle is switched off. RAPEX notification A12/0367/18 from March 2018.

Insufficient corrosion protection on the rear axle crossmembers leads to perforation. Can suddenly alter rear wheel alignment and impair handling. RAPEX notification A12/0243/15.

Rear axle control arms can detach and suddenly alter rear wheel alignment, leading to dangerous handling. Recall for affected vehicles.

Faulty ABS wheel speed sensors trigger permanent ABS and ESC warning lights. Fault codes point to individual wheel sensors. Repair is straightforward and inexpensive.

The Sonata NF is now 15–20 years old — radiator, thermostat and coolant hoses should be treated as consumable items. On an 8-year-old example in 2013, cavity sealing was discussed in owner communities as an urgent topic.

On the Sonata NF, cavity protection is strongly recommended once the vehicle is 8+ years old. Without treatment underbody panels and cavities rust significantly — especially in salt-belt regions.

The Sonata NF alternator is a weak point at high mileages. Early signs are battery warning light and low charge state on night drives.

Trunk and underbody rust significantly with inadequate maintenance. Cavity wax treatment is strongly recommended as a preventive measure. Particularly imported vehicles are affected.