Subaru Legacy BN/BS (2015-2019) Service Manual: Engine noise inspection

Subaru Legacy BN/BS (2015-2019) Service Manual / Mechanical(h6do) / Engine noise inspection

Type of sound	Condition	Possible cause
Regular clicking sound	Sound increases as engine speed increases.	• Valve mechanism is defective • Incorrect valve clearance • Worn camshaft • Broken valve spring • Trouble of valve lifter
Heavy and dull clank	Oil pressure is low.	• Worn camshaft main bearing • Worn connecting rod bearing (large end)
Heavy and dull clank	Oil pressure is normal.	Damaged front mount
High-pitched clank	Sound is noticeable when accelerating with an overload condition.	• Ignition timing advanced • Accumulation of carbon inside combustion chamber • Wrong heat range of spark plug • Improper octane value gasoline
Clank noise when engine speed is between 1,000 and 2,000 r/min	Noise is reduced when fuel injector connector of noisy cylinder is disconnected. *	• Worn crankshaft main bearing • Worn connecting rod bearing (large end)
Knocking sound when engine is operating under idling speed and engine is warm	Noise is reduced when fuel injector connector of noisy cylinder is disconnected. *	• Worn cylinder liner and piston ring • Broken or stuck piston ring • Worn piston pin and hole at piston end of connecting rod
	Sound is not reduced if each fuel injector connector is disconnected in turn.*	• Unusually worn valve lifter • Worn cam gear • Worn camshaft journal bore in cylinder head
Squeaky sound	—	Insufficient generator lubrication
Rubbing sound	—	Poor contact of generator brush and rotor
Gear scream when starting engine	—	• Defective ignition starter switch • Worn gear and starter pinion
Sound like polishing glass with a dry cloth	—	• V-belt • Defective water pump shaft
Hissing sound	—	• Insufficient compression • Air leakage in air intake system, hose, connection or manifold
Timing chain noise	—	• Loose timing chain • Timing chain contacting with adjacent part
Valve lifter noise	—	Incorrect valve clearance

* When disconnecting the fuel injector connector, the malfunction indicator light illuminates and DTC is stored in ECM memory. Therefore, perform the Clear Memory Mode Clear Memory Mode > OPERATION and Inspection Mode Inspection Mode > PROCEDURE after connecting the fuel injector connector.

Crankshaft specification

Refer to “Cylinder Block” for removal and installation procedures of the crankshaft. Cylinder Block > REMOVAL Cylinder Block > INSTALLATION ...

Engine oil pressure inspection

1. Disconnect the ground terminal from battery sensor. NOTE2. Remove the oil pressure switch from the oil pan upper. Oil Pressure Switch > REMOVAL3. Attach the oil pressure gauge to the oil pan uppe ...

Other materials:

Inspection
1. Check the identification (a) of the VDC control module & hydraulic control unit (VDCCM&H/U).NOTE:For the identification, refer to “SPECIFICATION” in “General Description”. General Description > SPECIFICATION2. Check the condition of connection and settlement of connector, ...