Valve Train Diagnosis General Diagnosis
| Table 1: | Momentary Noise On Engine Startup |
| Table 2: | Intermittent Noise on Idle Only |
| Table 3: | Noise at Slow Idle |
| Table 4: | Lifter Noise at High Vehicle Speeds |
| Table 5: | Noise at Idle, Becomes Louder at High Engine Speed |
| Table 6: | Valve Noise Regardless of Engine Speed |
A light tapping at one-half engine speed, or any varying frequency, can indicate a valve train problem.
These tapping noises increase with engine speed.
Before attempting to judge the valve train noises thoroughly warm up the engine. By doing this you will bring all engine components to a normal state of expansion. Also, run the engine at various speeds and listen for engine noise with the hood closed while sitting in the driver's seat. The causes of the valve train noise include the following conditions:
| • | Incorrectly adjusted valve lash |
| • | Low oil pressure |
| • | Loose valve rocker arm attachments |
| • | Worn valve rocker arm and/or pushrod |
| • | Broken valve spring |
| • | Sticking valves |
| • | Lifters worn, dirty or faulty |
| • | Camshaft lobes worn |
| • | Worn valve guides |
| • | Worn or damaged valve keys |
| • | Bent pushrods |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: Valve train noise disappears after 1 to 2 minutes | ||||
1 | This condition is normal. Oil drains from the lifters which hold the valves open when the engine is not running. The valve lifter needs a few seconds to fill with oil after you start the engine. Did you allow the valve lifters to fill? | -- | No correction is needed | -- |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: Intermittent noisy on idle only, disappears when engine speed increases | ||||
1 |
Are the valve lifters dirty? Are the valve lifters damaged? | -- | System OK | |
2 | Replace the valve lifters. Did you replace the valve lifters? | -- | System OK | -- |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: Noisy at slow idle or with hot oil; quiet at higher engine speeds or with cold oil | ||||
1 | Inspect the valve lifter for high lay down rate. Does the valve lifter have a high leakdown rate? | -- | Replace the faulty valve lifter | No correction is needed |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: Valve lifters noisy at high vehicle speeds, quiet at low speeds | ||||
1 | Check for a high engine oil level. An oil level above the FULL mark allows the crankshaft counterweights to churn the engine oil into foam. When foam is pumped into the valve lifters, the valve lifters become noisy since a solid column of oil ensures proper operation. Is the engine oil level too high? | -- | Drain the engine oil to the proper level | |
2 | Check for a low engine oil level. Oil level below the ADD mark allows the oil pump to pump air at high speeds. This causes noisy valve lifters. Is the engine oil level too low? | -- | Add engine oil as required | |
3 | Check the oil pan. Is the oil pan bent against the oil pump pickup? | -- | Repair as required | |
4 | Check the oil pump screen. Is the oil pump screen bent or loose? | -- | Repair as required | System OK |
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
DEFINITION: Noisy at idle, becoming louder as engine speed increases to 1,500 RPM | ||||||||||||||
1 | This noise is not connected with valve lifter malfunction. The noise becomes noticeable in the vehicle at speeds of 10-15 mph in L (Low) range, or speeds of 30-35 mph in D (Drive) range. The noise is described as a ticking sound. At slow idle, the sound may be entirely gone or appear as a light ticking noise in one more valves. This noise is caused by one or more of the following:
Are any components damaged or worn excessively? | -- | Repair as necessary | |||||||||||
2 | The noise may be an off-square valve spring. You can eliminate this noise by rotating the valve spring and valve.
Is the valve spring off-square? | -- | -- | |||||||||||
3 | If the valve spring is more than 1.6 mm (1/16 in) off-square, replace the valve spring. Did you complete the valve spring replacement? | -- | System OK | -- | ||||||||||
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
DEFINITION: Valve lifter noise louder as engine speed increase hot or cold engine. | ||||||||
1 |
Is the valve pushrod upper end ball worn? | -- | Replace the valve pushrod and valve rocker arm | |||||
2 | Check for a bent valve pushrod. Is the valve pushrod bent? | -- | Replace the valve pushrod | |||||
3 | Check the lubrication system feed to the valve pushrod and check to see if the valve pushrod is properly lubricated. Is the valve pushrod and feed system properly lubricated? | -- | Replace the valve pushrod and valve rocker arm | |||||
4 | Check for a loose or damaged valve rocker arm. Is the valve rocker arm loose or damaged? | -- | Replace the valve rocker arm | |||||
5 | If you do not need to replace the valve pushrod or the valve rocker arm, this indicates trouble in the valve lifter or camshaft. Is the camshaft worn or damaged? | -- | Replace the camshaft and valve lifters | Replace the valve lifter(s) as necessary | ||||
