Engine Noise Diagnosis. GMC Truck GMC K Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Pickup - 4WD 🢒 Engine 🢒 Engine Mechanical - 6.5L 🢒 Engine Noise Diagnosis

Table 1:	Engine Knock Noise (Fuel Knock)
Table 2:	Intermittent Noise on Idle Only, Disappearing When Engine Speed Is Increased
Table 3:	Noise at Slow Idle or With Hot Oil; Quiet at Higher Engine Speeds or With Cold Oil
Table 4:	Noise at High Vehicle Speeds, Quiet at Low Vehicle Speeds
Table 5:	Noise Regardless of Engine Speed
Table 6:	Valve Train Noise
Table 7:	Vibrating or Rattling from Exhaust System
Table 8:	Exhaust Leakage and/or Noise

Condition

Action

DEFINITION: A stuck fuel injection nozzle can cause a knocking noise similar to a damaged piston, rod, or rod bearing.

Leaking fuel injection nozzle

•	Use the cylinder balance diagnostic procedure to help locate the cylinder that is the source of the noise.

•	Exchange the fuel injection nozzle for one in an adjacent cylinder to see if the condition persists.

•	If the condition follows the fuel injection nozzle to the adjacent cylinder, and disappears from the original cylinder, the fuel injection nozzle is at fault.

Exchange or replace the fuel injection nozzle.

•	If the condition does not change, or you still cannot locate the cylinder that is the source of the noise, diagnose the engine for mechanical damage.

Condition	Action
DEFINITION: Contaminated or insufficient oil supply can cause intermittent noise from valve train components.
Dirt in the valve lifter	Replace all damaged components.
Pitting on the valve lifter check ball	Replace all damaged components.

Condition	Action
DEFINITION: Possible causes of the intermittent noise include the following conditions:
High valve lifter leak down rate	Repair or replace all damaged components.

Condition	Action
DEFINITION: Possible causes of the intermittent noise include the following conditions:
High engine oil level	An oil level above the FULL mark allows crankshaft counterweights to churn the oil into foam. When foam is pumped into the valve lifters, they will become noisy, as a solid column of oil is required for proper operation. Drain engine oil to the proper level.
Low engine oil level	An oil level that is below the ADD mark allows the oil pump to pump air at high speeds, which results in noisy valve lifters. Fill engine oil to the proper level.
Oil pan bent against the oil pump pickup tube or screen	Repair or replace all damaged components.
Oil pump pickup tube or screen bent or loose	Repair or replace all damaged components.

Condition	Action
DEFINITION: Possible causes of the noise include the following conditions:
Excessive valve lash	Check for valve lash by turning the engine so that the piston in that cylinder is on TDC of the firing stroke. If the valve lash is correct, the pushrod can be moved up and down a small amount with the valve rocker arm held against the valve.
Worn pushrod upper end ball	Repair or replace all damaged components.
Bent pushrod	Repair or replace all damaged components.
Improper lubrication of the pushrod	Repair or replace all damaged components.
Loose or damaged valve rocker arm	Repair or replace all damaged components.
Damaged or failed lifter	Repair or replace all damaged components.

Condition	Action
DEFINITION: The following conditions may cause valve train noise:
Low oil pressure	Repair or replace all damaged components.
Loose valve rocker arm attachments	Repair or replace all damaged components.
Worn valve rocker arm and/or pushrod	Repair or replace all damaged components.
Broken valve spring	Repair or replace all damaged components.
Sticking valve	Repair or replace all damaged components.
Worn, dirty or faulty valve lifter	Repair or replace all damaged components.
Worn or faulty camshaft	Repair or replace all damaged components.
Worn valve guide	Repair or replace all damaged components.

Condition

Action

DEFINITION: Vibration or rattling from the exhaust system may be caused by loose and/or misaligned exhaust components.

Vibration or rattle noise

•	Align and tighten all connections.

•	Repair or replace all damaged components.

Condition	Action
DEFINITION: Possible causes of the noise include the following conditions:
Leakage at one or more of the exhaust system joints and/or couplings	Repair or replace all damaged components.
Improperly installed or misaligned exhaust system	Repair or replace all damaged components.
Cracked or broken exhaust manifold	Repair or replace all damaged components.
Leak between the exhaust manifold and the cylinder head	Repair or replace all damaged components.
Burned, blown or rusted out exhaust pipe or muffler	Repair or replace all damaged components.