Mitsubishi L200 (Triton) 2.4 DI-D 4N15 (2016): Valve Train Check and Hydraulic Lash Adjuster Diagnosis

Part numbers are from the manufacturer's original catalogue. Check them against your VIN before ordering.

• socket set and ratchet
• torque wrench
• mechanic's stethoscope
• OBD scanner
• clean oil container
• shop rags

1. Identify the type of noise: ticking on a cold engine that goes away after 1-3 minutes of warm-up usually points to oil draining out of the hydraulic lash adjusters. Constant ticking on a warm engine points to a worn or stuck adjuster, or a worn cam lobe or rocker arm.
2. Check the oil level and condition. The level should be between the dipstick marks, and the oil should not be heavily diluted with fuel or overloaded with soot. Diluted or contaminated oil, as well as overfilling or underfilling, produces the same symptoms as faulty adjusters.
3. Check for fault codes and whether the oil pressure warning light comes on. Read the codes with an OBD scanner.
4. If the oil is old or does not meet the specification, replace the oil and oil filter and check the noise again after 200-300 km. This is often enough.
5. If the noise remains, listen with a stethoscope along the cylinder head cover, cylinder by cylinder, to tell the valve train apart from the injectors (DI-D injectors also click), the fuel pump, the timing chain and the accessories.
6. To inspect the valve train, remove the engine cover, disconnect the ventilation hoses and connectors that block removal of the valve cover, and loosen its bolts evenly, working from the edges to the center. Check the exact sequence and the list of parts to disconnect on the 4N15 against your specific trim and market (it differs depending on the market and emissions class).
7. Inspect the rocker arms, rollers, camshaft lobes and hydraulic lash adjusters. Look for scoring, pitting, roller wear and dark discoloration from overheating. Replace any part with obvious wear. You can test an adjuster by pressing on it: a good one should not "sink" under hand pressure, while a stuck or collapsed one either sinks or, conversely, stays rigid at zero clearance.
8. Before reassembly, clean the cylinder head and cover mating surfaces of old sealant and oil, and install a new valve cover gasket (if needed, apply sealant at the joints as recommended by the gasket manufacturer).
9. Tighten the valve cover bolts evenly, from the center to the edges, with a low torque. For bolts like these it is usually around 4-6 N·m (3-4 lb-ft); the exact value is in the manufacturer's manual. Do not overtighten: the cover is plastic or aluminum, deforms easily and will start to leak.
10. Reinstall the hoses and connectors, add oil if needed, start the engine and let it run. Check for leaks and whether the noise has returned. Cranking the engine with the starter without starting it until oil pressure builds is not required, but on a badly neglected engine the adjusters may take several minutes to "pump up".
11. If the ticking persists after the oil change and replacement of clearly worn parts, check the oil pressure with a gauge and inspect the oil pump and the oil pickup screen. This diagnosis is best left to a repair shop.

• Do not try to "adjust" the clearance by turning anything: the 4N15 has no such adjustment, and replacing the hydraulic lash adjusters without a reason will accomplish nothing
• If you hear a metallic knock under load, it may come from the timing chain or the connecting rod bearings
• With that kind of noise, it is best to stop driving the vehicle and take it to a repair shop, otherwise serious engine damage is possible