Brand New G4KJ 2.4L GDI Petrol Long Engine for Hyundai Sonata LF 2015-2020

About this engine

Between 2015 and 2020 the Hyundai Sonata LF offered Australian drivers a lot of car for the money: a quiet cabin, generous equipment and a G4KJ 2.4-litre GDI petrol engine doing the work up front. These sedans routinely rack up big highway kilometres, and it is usually the engine, not the body or interior, that ends their service life. Rather than sending a straight, well-kept Sonata to auction, fitting a brand-new long engine returns it to dependable daily duty for years.

Engine Zone supplies this G4KJ as a new unit, never reconditioned, built to OEM fitment specification throughout. Every engine is run through hot and cold testing after assembly, ships freight-free to any point in Australia, and is backed by a parts warranty of 12 months or 50,000 km, whichever occurs first. A free VIN check before purchase confirms it suits your exact car; call 1300 200 320.

G4KJ 2.4 GDI: design, history and common issues

Hyundai introduced the Theta four-cylinder in the mid-2000s and developed it into the Theta II, which went on to power an enormous number of Hyundai and Kia sedans and SUVs around the world. Within that family, the G4KJ is the 2.4-litre member with gasoline direct injection. Its port-injected sibling is the G4KE, the G4KG serves commercial applications, and the G4KH adds a turbocharger to a smaller-capacity version of the same architecture.

The design is thoroughly conventional in the best sense: aluminium block and head, twin overhead cams, four valves per cylinder and chain-driven timing with no belt service interval. What set the G4KJ apart in the Sonata LF was its injection system, which delivers fuel directly into each cylinder at high pressure. That allows a higher compression ratio than the port-injected engine and translates into stronger mid-range response and better economy at cruise.

The family's weakness is equally well documented. Connecting-rod bearing wear in high-kilometre Theta II engines became the subject of major manufacturer recalls and extended warranty programs in several markets. Once a bottom-end knock develops, the crankshaft and bearings are already damaged, and honest workshops will tell you that machining, parts and labour for a rebuild frequently add up to more than a new long engine. That economic reality, more than anything else, is why replacement has become the standard fix for a worn G4KJ. The replacement supplied here does not repeat the original's mistakes: it holds OEM fitment specification, but the internals are upgraded where the factory design showed documented weaknesses, using a higher-grade crankshaft, connecting rods, bearings and other stronger internal parts.

Fitment for Hyundai Sonata LF 2015-2020

This engine is intended for the Hyundai Sonata LF generation sold new in Australia from 2015 to 2020, in variants originally powered by the G4KJ 2.4 GDI. The Sonata line-up included more than one engine over that period, so we never assume fitment from the year and badge alone. Your VIN tells us exactly which driveline your car was built with, and we check it at no cost before dispatch on every single order, without exception.

Finding the VIN takes seconds: it is printed on your registration certificate and stamped on a plate visible through the lower corner of the windscreen. Send it through with your enquiry and our team will confirm the match, flag anything unusual about your build, and answer questions about the changeover. If you would rather talk it through first, 1300 200 320 reaches our team directly.

The swap itself is a like-for-like exchange for a competent workshop. All external hardware, from manifolds and the fuel rail to the alternator, compressor and engine wiring, unbolts from the tired engine and refits to the new one. Sensible workshops take the opportunity to renew the water pump, thermostat, belts, hoses and mounts while access is easy, and to clean any transferred intake components so the new engine is not breathing through old carbon deposits. Budget for fresh coolant and the correct grade of oil as part of commissioning; both matter to warranty compliance and to how long the new engine ultimately lasts in service.

Long engine inclusions and next steps

A long engine, as supplied here, means the complete rotating and reciprocating assembly inside a new block, topped with a new assembled cylinder head. Crankshaft, bearings, pistons, rings, rods, camshafts, valves and springs are all installed and set to factory tolerances. What it deliberately excludes are the bolt-ons your existing engine already has: intake and exhaust manifolds, injectors, throttle body and accessory drive components.

Every unit is hot and cold tested after assembly, which verifies oil pressure, compression and noise levels before the engine is signed off and crated. A heat tab is attached during the build; it is a one-way indicator that records overheating, and heat-related damage sits outside warranty cover because it points to a cooling-system or installation problem rather than a defect in the engine itself.

Warranty on parts runs 12 months or 50,000 km from purchase, whichever arrives first, conditional on installation by a qualified mechanic. Freight anywhere in Australia is part of the price, and we deliver to workshops, depots or homes. From your side the sequence is simple: VIN check, order, delivery, installation, then a normal gentle run-in period while the rings seat. An early oil and filter change after run-in is cheap insurance. Questions at any stage go to 1300 200 320.