Chevrolet 70 1969 Series, Shop Manual

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G ASO LIN E ENGINES 6A-21
LOW ENGINE OIL PRESSURE
(When checked with engine at normal operating temperature)
POSSIBLE C A USES R E M E D Y
1. Defective oil gauge or sending unit. 1. Check pressure with master gauge. Replace oil
gauge or sending unit if defective.
2. Oil viscosity too low. 2. Fill crankcase with correct oil.
3. Oil diluted with gasoline. 3. Check for indications of choke malfunction or
carburetor flooding allowing gasoline to enter
crankcase. Make necessary correction.
4. Suction loss. 4. Check for loose intake pipe and screen in oil
pan. Also check for partially clogged inlet screen.
5. Weak or broken relief valve spring in oil pump. 5. Inspect spring and replace if necessary.
ENGINE
S Y M P T O M A - V A L V E M E C H A N IS M NOISE
POSSIBLE CAUSES
1. Sticking valves.
2. Incorrect valve lash.
3. Bent push rod(s).
4. Worn rocker arms and/or shaft.
5. Broken valve spring.
6. Damaged valve lifter and/or camshaft.
NOISE
R E M E D Y
1. Clean and lubricate valve stems.
2. Adjust valve lash.
3. Determine and correct cause of push rod bend­
ing. Install new push rod.
4. Replace worn parts and make sure oil is reach
ing valve rocker arms.
5. Replace spring.
6. Replace lifter and/or camshaft.
S Y M P T O M B - BEARING NOISE
POSSIBLE CAUSES
1. Insufficient oil supply.
2. Low oil pump pressure.
3. Thin or diluted oil.
4 Excessive bearing clearance.
5. Piston pins loose fit in connecting rod or piston.
6. Piston to cylinder bore clearance excessive
(piston slap).
R E M E D Y
1. Check oil level and add oil as required.
2. Remove and inspect oil pump and inlet screen.
Make necessary corrections.
3. Change oil. Use oil with proper viscosity.
4. Remove oil pan and make bearing replacement
or repairs.
5. Install new piston pins (oversize pins if req'd.).
6. Overhaul engine.
N O T E : When diagnosing engine noise problems, be careful that noises caused by
accessories such as air compressor and power take-off are not mistaken for
engine noises. Removal of accessory drive belts will eliminate any noises caused
by these units.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHO P M ANUAL