GMC chervolet camaro 1999 Service Manual page 806

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Engine Engine Mechanical - 3.8 L 6-23
• Dirty, stuck, or worn valve lifters • Worn push rods
• Damaged or improperly machined camshaft lobes • Worn valve rocker arms
• Broken valve rocker arm bolt • Insufficient or poor oil supply to the valve train
(low oil pressure)
• Loose or worn valve rocker arm attachments
• Excessive valve stem-to-guide clearance
• Worn valve guides
• Missing or improperly positioned lifter guides (roller
lifter engines)
Momentary Noise on Engine Startup
Step
Action Value(s) Yes
No
DEFINITION: Momentary noise when the engine is started, usually cold
This condition is normal. Oil drains from the valve lifters
which hold the valves open when the engine is not
1
running. The valve lifter needs a few seconds to fill with oil
-
after you start the engine.
Repair as No correction is
Does the noise continue after a few seconds? required needed
Intermittent Noise on Idle Only
Step Action Value(s) Yes
No
DEFINITION: Intermittent noise on idle that disappears when engine speed increases
1. Disassemble the valve lifters.
1
2. Check the valve lifters for any dirt. Check the valve
-
lifters for a pitted or damaged check ball.
Replace the
Are the valve lifters dirty or damaged? valve lifter System OK
Noise at Idle
Step
I
Action
I
Value(s)
I
Yes
I
No
DEFINITION: Noise at idle or with hot oil that quiets at higher engine speeds or with cold oil
1
I
Inspect the lifter for a high leakdown rate.
l I
Replace the
I
No correction is
-
Does the lifter have a high leakdown rate?
faulty lifter needed
Noise at High Vehicle Speeds
Step
Action Value(s)
Yes
No
DEFINITION: Noise at high RPM only
Check for a high engine oil level. An oil level above the
FULL mark allows the crankshaft counterweights to churn
1
the oil into a foam. When the foam is· pumped into the
-
lifters, the lifters become noisy since a solid column of oil
ensures the proper operation.
Drain the oil to
Is the oil level too high? the proper level Go to Step2
Check for
a
low engine oil level. An oil level below the
2
ADD mark all.ows the oil pump to pump air at .high speeds.
This causes noisy valve lifters.
-
Add oil as
Is the oil level too low? required
Go to Step 3
3
Check the oil pan.
Repair as
-
Is the oil pan bent against the oil pump pickup? required
Go to Step 4
4
Check the .oil pump screen.
-
. Repair as
Is the oil pump screen
bent
or loose? required System
OK