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Autopapyrus · Kia Optima 2.4 GDI G4KJ (2019)
https://autopapyrus.com/guides/kia/optima/camshaft-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Kia Optima 2.4 GDI G4KJ (2019): Camshaft Replacement

The G4KJ 2.4 GDI engine is chain-driven, with variable valve timing on both camshafts and a high-pressure fuel pump driven by the camshaft. Camshaft replacement is usually needed because of scored journals, worn lobes, or after oil-related problems. The exact procedure for this model is not documented in publicly available service materials, so the general principle and work sequence are given below. Check tightening torques and tightening sequences against the manufacturer's service manual.

Difficulty: Hard Time: 6-10 hours (depending on experience and chain condition) Steps: 14 Tools: Socket set and ratchet, torque wrench (low range 5-60 N·m), Torx and E-type sockets, camshaft holding tool or wrench for holding the camshafts by their flats, hex keys, puller or pry tools, clamps or locking pins to secure the chain, container for oil and coolant, sealant for oil-contact surfaces, clean shop rags, marker or paint for alignment marks.

Parts

2
  • 🔩 Intake camshaft (assembly): catalog number for the Optima 2.4 is 241002GTB0
  • 🔩 exhaust camshaft: 242002GTA0. Verify the part numbers by VIN in the catalog before ordering, since the G4KJ comes in versions for different markets. Also: gasket and seal kit (valve cover gasket, spark plug well seals, oil seals), engine oil and oil filter, and, if needed, timing chain, tensioner, chain guides, CVVT phasers, and lifters or rocker arms. Check chain and phaser pricing with your supplier
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 4 more. See manuals →

Step by step

14 steps
  1. Disconnect the battery (negative terminal). Remove the engine cover, the air intake duct, and the air filter housing. Drain the coolant if you need access to the hoses, and drain the engine oil so it doesn't flood the chain and cylinder head.
  2. Remove the ignition coils and disconnect the sensor connectors on the valve cover. Disconnect the crankcase ventilation hoses. Be careful not to damage the plastic fittings and connectors, as they are brittle.
  3. Remove the fuel rail and the high-pressure pump. First relieve the fuel system pressure (pull the fuel pump fuse or relay and run the engine until it stalls to use up the remaining fuel). Disconnect the high-pressure line carefully and plug the open ports to keep dirt out. GDI injectors are very sensitive to contamination.
  4. Remove the valve cover: loosen the bolts in a spiral pattern from the edges toward the center, and clean the mating surfaces of old sealant. Do not pry the cover along its sealing surface with a screwdriver.
  5. Rotate the crankshaft in its normal direction of rotation until cylinder 1 is at TDC on the compression stroke. Align the marks on the pulley or damper and on the camshaft sprockets. Use paint to put reference marks on the chain and sprockets (chain relative to the sprockets) so you don't lose the timing.
  6. Secure the chain to keep the teeth from skipping (with wire, a zip tie, or a holding tool). If you need to take the chain off a camshaft, first release the tensioner as specified in the service manual: the hydraulic chain tensioner may have a locking pin. Do not turn the crankshaft with the camshafts removed and the chain slack.
  7. Remove the CVVT phaser bolts on the camshafts, holding each camshaft by its flats with a wrench. Remove the phasers carefully without striking them, and do not disassemble or rotate their internal mechanism. Keep dirt out of the CVVT oil passages.
  8. Loosen the camshaft bearing cap bolts evenly in 2-3 passes, from the center outward, following the pattern in the service manual. Remove the caps, noting their position and orientation (they are numbered or marked). Lift out the camshafts.
  9. Inspect the bearing seats in the cylinder head, the journals, and the lobes. If the seats are scored or worn, replace the camshaft and have the cylinder head checked as well. Measure the journal clearances (Plastigage or micrometer) and compare them with the service manual tolerances. Check the lifters or rocker arms for wear.
  10. Lubricate the journals and lobes of the new camshafts with engine oil or assembly lube. Lay the camshafts in so the marks match the TDC position, and install the caps in their original order and orientation. Tighten the cap bolts in 2-3 passes from the center outward. The tightening torque is low, around 10-20 N·m (7-15 lb-ft); use the exact value from the service manual.
  11. Install the phasers and sprockets according to the marks and tighten the bolts with a torque wrench to the specified value while holding the camshaft. Check the chain tension and that all marks line up, then turn the crankshaft by hand 2 full revolutions and check the TDC marks again. If the marks do not line up, do not start the engine; sort out the timing first.
  12. Install a new seal (if applicable) and a new valve cover gasket, and apply sealant at the locations specified in the service manual (the joints of the half-round plugs, and the corners). Tighten the valve cover bolts evenly from the center outward. The torque is low, around 8-12 N·m (6-9 lb-ft); use the exact value from the service manual.
  13. Install the high-pressure pump and the rail with new O-rings lubricated with engine oil. Tighten to the specified torque. Install the coils, hoses, air intake duct, and everything else you removed. Fill with the correct amount and viscosity of engine oil, and top off the coolant if needed.
  14. Reconnect the battery. Before starting, crank the engine with the starter for a few seconds with the fuel pump fuse removed to build oil pressure, then reinstall the fuse and start the engine. Let it run, and check for leaks, fault codes, and unusual chain noise. Read the codes for the valve timing system and, if necessary, reset the adaptations.

Common mistakes and warnings

  • Working on the chain drive and valve timing takes experience: if the marks are set incorrectly, the valves will hit the pistons and the engine will be damaged. If you lack experience, leave the job to a specialist repair shop. The GDI fuel system operates under high pressure (tens to hundreds of bar), so relieve the pressure before disassembly, avoid open flames, and protect your eyes. Take all tightening torques, the bearing cap tightening sequence, and clearance tolerances from the manufacturer's service manual for your engine, not from similar engines.