Engine Mechanical Diagnosis - Pontiac TRANS AM 1977 Service Manual

6A-2
1977 PONTIAC SERVICE MANUAL
ENGINE MECHANICAL DIAGNOSIS
CONDITION POSSIBLE CAUSE CORRECTION
Excessive Oil Loss a. External oil leaks. 1. Tighten bolts and/or replace
gaskets and seals as necessary.
b. Improper reading of 1. Check oil with car on a
dipstick. level surface and allow adequate
drain down time. NOTE: On 140
L-4 engines, oil check should
be made 30 minutes after hot
shut off.
c. Improper oil viscosity.
1. Use recommended S.A.E.
viscosity for prevailing
temperatures.
d. Continuous high speed 1. Continuous high speed
driving and/or severe operation and/or severe
usage such as trailer usage will normally cause
hauling.
,
decreased oil mileage.
e. P.C.V. system 1. Service as necessary.
malfunctioning.
f. Valve guides and/or 1. Ream guides and install
valve stem seals worn. oversize service valves
and/or new valve stem seals.
g. Piston rings not 1. Allow adequate time for
seated, broken or worn.
rings to seat.
2. Replace broken or worn
rings as necessary.
Low Oil Pressure
a. Incorrect or
malfunctioning
oil pressure switch.
b. Slow idle speed.
c. Improper oil viscosity
or diluted oil.
d. Oil pump worn
or dirty.
e. Plugged oil filter.
f. Oil pickup screen
loose or plugged.
g. Hole in oil pickup
tube.
h. Excessive bearing
clearance.
i. Cracked or porous
oil galleys.
j. Poor seal at timing
cover gasket (23 1
engine only).
1. Replace with proper switch.
1. Set idle speed to spec.
1. Install oil of proper
viscosity for expected
temperature.
2. Install new oil if diluted
with moisture or unburned
fuel mixtures.
1. Clean pump and replace
worn parts as necessary.
1. Replace filter and oil.
1. Clean or replace screen
as necessary.
1. Replace tube.
1. Replace as necessary.
1. Repair or replace block.
1. Replace gasket.