General Information
| • | A light tapping 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. Also, while sitting in the drivers seat, run the engine at various speeds and listen for abnormal noise. |
| The causes of the valve train noise may include the following conditions: |
| • | Low engine oil pressure |
| • | Refer to Oil Pressure Diagnosis and Testing . |
| • | Worn or faulty oil pump |
| • | A loose or plugged oil pump screen |
| • | Loose valve rocker arm attachments (causing excessive valve lash) |
| • | Worn of 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 valve lifter 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 |
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? | -- | System OK | |
2 | Check for a high engine oil level. A 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 | |
3 | Check for a low engine oil level. A 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 | |
4 | Check for proper engine oil pressure. Refer to Engine Mechanical Specifications and Oil Pressure Diagnosis and Testing . Is the engine oil pressure within specifications? | -- | ||
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 | |
6 | Check for a damaged oil pump or loose mounting bolts Refer to Oil Pump Clean and Inspect Is the oil pump damaged or are the fasteners loose? | -- | Repair as required. System OK | |
7 | Remove and inspect the valve lifters, rocker arms, and pushrods. Refer to Valve Train Components Clean and Inspect (Rocker Arms and Pushrods) and Valve Train Components Clean and Inspect (Valve Lifters and Guides) . Are components worn or damaged? | -- | Replace the components as required. System OK | |
8 | Perform a camshaft lobe lift test. Refer to Camshaft and Bearings Clean and Inspect Is the test within Engine Mechanical Specifications | -- | Camshaft is OK | Replace the camshaft and valve lifters. System OK |
9 | Remove the engine front cover and inspect the timing chain and sprockets for for excessive wear or damage. Refer to Valve Train Components Clean and Inspect (Sprockets and Chain) Are the components worn or damaged? | -- | Replace the components as required. System OK | |
10 | Perform a complete disassembly of the engine and inspect all components. | -- | -- | -- |
