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Autopapyrus · Hyundai Sonata 2.4 GDI G4KJ (2018)
https://autopapyrus.com/guides/hyundai/sonata/camshaft-and-hydraulic-lash-adjuster-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Hyundai Sonata 2.4 GDI G4KJ (2018): Camshaft and Hydraulic Lash Adjuster Replacement

The G4KJ (Theta II 2.4 GDI) is an engine with a chain-driven valve train, two camshafts, and CVVT phasers on both camshafts. Accessing the camshafts requires removing the chain from the sprockets and precisely aligning the timing marks during reassembly. This job is suitable for an experienced mechanic. Check the exact torque values and the bolt tightening sequence for this engine against the factory service manual; the values below are for reference only.

Difficulty: Hard Time: 8-14 hours (including timing chain removal and installation and valve timing verification) Steps: 19 Tools: Socket set and ratchet, torque wrench (5-60 N·m range), camshaft sprocket/pulley holding tool, paint marker or paint, valve keeper removal tool set and tweezers, magnetic pickup tool, clean container with oil for soaking the lash adjusters, sealant where specified by the service manual, new valve cover gasket, timing chain consumables as needed.

Part

  • 🔩 Intake camshaft and exhaust camshaft (each sold separately), hydraulic valve lash adjusters (one per valve, set for 16 valves), and, if worn, rocker arms with rollers. Additionally: valve cover gasket, spark plug well seals, engine oil and oil filter
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Chilton and 5 more. See manuals →

Step by step

19 steps
  1. Let the engine cool down and disconnect the negative battery terminal. Remove the engine cover and drain the oil if you plan to change it (recommended after the job).
  2. Relieve the pressure in the fuel rail: on a GDI engine the rail holds high pressure. Shut the engine off and let it cool, and do not loosen the high-pressure fuel lines while they are under pressure. Disconnect the connectors of the injectors, ignition coils, and the sensors on the valve cover, and carefully move the wiring harnesses out of the way.
  3. Remove the ignition coils and, if necessary, the spark plugs. Remove the air intake duct and any related intake components that block access to the valve cover.
  4. Remove the vacuum hoses and crankcase ventilation hoses, then remove the valve cover: loosen the bolts in a spiral pattern from the edges toward the center, and pry the cover off carefully without prying at the sealing surface with a screwdriver.
  5. Set the engine to TDC on the compression stroke of cylinder 1 using the marks on the camshaft sprockets and the crankshaft pulley. Paint-mark the chain and the camshaft sprockets so you can check alignment during reassembly.
  6. On a GDI engine, the high-pressure fuel pump is driven by a camshaft lobe. If the pump is in the way, remove it per the service manual (this engine's pump delivers fuel at very high pressure, so make sure the pressure has been relieved before disconnecting the lines, and replace the pump's lines and seals with new ones if the service manual says so).
  7. Remove the timing chain tensioner (or lock it per the procedure if it stays in place) to slacken the chain. Open up access to the camshaft sprockets.
  8. Loosen the camshaft sprocket (CVVT) bolts while holding the camshafts so they cannot turn. Do not disassemble the phasers. Remove the sprockets from the camshafts and tie the chain up with wire so it does not fall into the engine.
  9. Loosen the camshaft bearing cap bolts evenly in several passes, working from the edges toward the center (or in the reverse of the service manual tightening sequence). Remove the bearing caps, note their positions (they are marked), and remove the camshafts.
  10. Remove the hydraulic lash adjusters and rocker arms (if your design has them), laying them out in order (by cylinder) so you can check for wear. Inspect the rocker arm rollers and contact surfaces for wear, chipping, and scoring.
  11. Clean the mating surfaces, oil passages, and seats. Before installation, soak the new hydraulic lash adjusters in clean oil as the manufacturer recommends so they fill up, otherwise you will hear ticking after startup.
  12. Lubricate the camshaft journals and bearing seats with engine oil (assembly lube is acceptable). Install the rocker arms and lash adjusters, then the camshafts with their marks in the position specified by the service manual, and the bearing caps according to their marks.
  13. Tighten the bearing cap bolts in 2-3 passes from the center toward the edges. Torque values for this engine family are low, usually around 10-20 N·m (7-15 lb-ft) for the camshaft caps; use the exact value from the service manual.
  14. Install the sprockets and chain according to the paint and timing marks, and tighten the CVVT sprocket bolts with a torque wrench (the torque is high, approximately 50-80 N·m (37-59 lb-ft); use the exact value from the service manual, and always hold the camshaft against turning). Reinstall the chain tensioner.
  15. Turn the crankshaft by hand through 2 revolutions and check that the timing marks line up. The camshafts should return to their original position without binding. If you have any doubts, redo the timing setup.
  16. Install the high-pressure pump (if removed) and the valve cover with a new gasket (apply sealant at the half-moon plug joints as specified by the service manual), and tighten the cover in a spiral pattern from the center toward the edges with low torque (about 8-12 N·m (6-9 lb-ft); confirm with the service manual).
  17. Reinstall all removed parts, add fresh oil, and install a new filter. Connect the battery.
  18. Before starting, check for leaks by cranking the engine with the starter without starting it (you can disable the fuel pump by pulling its fuse) until oil pressure appears. Start the engine and let it warm up. Lash adjuster ticking may occur for the first few minutes until they fill with oil. If it does not go away within 5-10 minutes, shut the engine off and check the assembly.
  19. Read and clear the fault codes (especially those for valve timing and camshaft/crankshaft correlation), take a test drive, and do a final check for oil leaks.

Common mistakes and warnings

  • Starting an engine with incorrectly set timing marks, without first turning it over by hand, can cause the pistons to collide with the valves and lead to expensive repairs. The GDI fuel system operates at very high pressure, so do not loosen the high-pressure lines on a hot engine or without relieving the pressure. If you have no experience with chain-driven valve trains and torque wrenches, leave the job to a repair shop. Camshaft and lash adjuster wear is often caused by the oil: before reassembly, check the condition of the oil passages and use oil of the correct viscosity grade.