Valve Train Diagnosis. GMC Truck Yukon

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Yukon - 2WD 🢒 Engine 🢒 Engine Mechanical - 4.8L, 5.3L, and 6.0L 🢒 Valve Train Diagnosis

General Information

Symptom

Cause

•	A light tapping noise at one-half engine speed, or any varying frequency, may indicate a valve train problem.

•	These tapping noises will typically increase with engine speed.

•	Before attempting to diagnose valve train noise, check for the proper oil level and thoroughly warm up the engine.

By doing this you will bring all engine components to a normal state of expansion.

•	While sitting in the drivers seat, run the engine at various speeds and listen for any abnormal engine noise.

•	Whenever Valve Lifter Diagnosis is necessary, always use a listening device such as an engine stethoscope, or listening ears J 39565. These tools will help to isolate any lifter noise and identify noises that could be mis-diagnosed as lifter noise.

A light tapping noise similar to valve train noise may be caused by the following components:

•	Fuel Injectors

•	Evaporative emission (EVAP) purge solenoid or damaged or missing isolator

•	Detonation

•	Loose heat shields

The Causes of Valve Train Noise May Include the Following Conditions:

•	Low engine oil pressure

•	Worn or faulty oil pump

•	A loose or plugged oil pump screen

•	Loose valve rocker arm attachments, causing excessive valve lash

•	Worn or damaged valve rocker arm bearings

•	Worn valve rocker arm and/or pushrod

•	Broken valve spring

•	Sticking valves

•	Valve lifters worn, dirty, or faulty

•	Broken valve lifter guide

•	Camshaft lobes worn

•	Worn valve guides or valve stems

•	Worn or damaged valve keys

•	Bent pushrods

•	Excessive play in the camshaft timing chain

•	Bent, broken, or damaged timing chain sprocket teeth

Diagnostic Table

Step	Action	Value(s)	Yes	No
DEFINITION: A light tapping noise at one half engine speed, or any varying frequency.
1	Is there valve train noise?	--	Go to Step 2	System OK
2	Check for a high engine oil level. An engine with the oil level above the FULL mark allows the crankshaft counterweights to churn the oil into foam. When foamy oil is pumped into the lifters, the lifters become noisy. A solid column of oil ensures proper lifter operation. Is the oil level too high?	--	Drain the oil to the proper level. System OK	Go to Step 3
3	Check for a low engine oil level. An engine with the oil level below the ADD mark may allow the oil pump to pump air at high engine RPM's. Is the oil level too low?	--	Add oil as required. System OK	Go to Step 4
4	Check for proper engine oil pressure. Refer to Oil Pressure Diagnosis and Testing and Engine Mechanical Specifications . Is the engine oil pressure within specifications?	--	Go to Step 7	Go to Step 5
5	Check the oil pump screen for damage or a loose fit to the oil pump. Inspect for a missing or damaged oil pump screen O-ring seal. Is the oil pump screen loose or is the screen or O-ring seal damaged?	--	Repair as required. System OK	Go to Step 6
6	Check for a damaged oil pump or loose mounting bolts Refer to Oil Pump, Screen and Crankshaft Oil Deflector Installation . Is the oil pump damaged or are the fasteners loose?	--	Repair as required. System OK	Go to Step 10
7	Remove and inspect the valve lifters, rocker arms, and pushrods. Refer to Valve Lifters and Guides Cleaning and Inspection and Valve Rocker Arm and Push Rod Cleaning and Inspection . Are components worn or damaged?	--	Replace the components as required. System OK	Go to Step 8
8	Perform a camshaft lobe lift test. Refer to Camshaft and Bearings Cleaning and Inspection and Engine Mechanical Specifications .	--	Camshaft is OK Go to Step 9	Replace the camshaft and valve lifters. System OK
9	Remove the engine front cover and inspect the timing chain and sprockets for excessive wear or damage. Refer to Camshaft Timing Chain and Sprocket Cleaning and Inspection . Are the components worn or damaged?	--	Replace the components as required. System OK	Go to Step 10
10	Perform a complete disassembly of the engine and inspect all components. Are the components worn or damaged?	--	Replace the components as required.	System OK