Buick LeSabre 1965 Service Manual page 48

2 - 2 6 TROUBLE DIAGNOSIS
ENGINE
wearing surfaces. Replace faulty
parts.
(4) Valves and Seats Cut Down
Excessively. Noisy and improper
valve lifter operation may result
if a valve and its seat have been
refinished enough to raise the end
of the valve stem approximately
.050" above normal position. In
this case it will be necessary to
grind off end of valve stem or
replace parts.
The normal height of the valve
stem above the valve rocker arm
gasket surface of the cylinder
head is 1.540".
(5) Faulty H y d r a u l i c Valve
Lifters. If the preceding sug-
gestions do not reveal the cause
of noisy valve action, check op-
eration of the hydraulic valve
lifters as described in subpara-
graph c.
c. Checking Hydraulic Valve
Lifters
When checking hydraulic valve
l i f t e r s , remember that grit,
sludge, varnish or other foreign
matter will seriously affect op-
eration of these lifters. If any of
these f o r e i g n substances are
found in the lifters or anywhere
in the engine where they may be
circulated by the lubrication sys-
tem, a thorough cleaning job must
be done to avoid a repetition of
valve lifter trouble.
To guard against entrance of grit
into the lifters the engine oil must
be changed as recommended in
paragraph 1-1 and the oil filter
element must be changed as rec-
ommended in paragraph 1-2. The
engine oil must be the heavy duty
type (MS) to avoid detrimental
formation of sludge and varnish.
The car owner should be speci-
fically advised of these require-
ments when the car is delivered.
Faulty valve lifter operation usu-
ally appears under one of the
following conditions.
(1) Rapping Noise Only When En-
gine is Started. When engine is
stopped any lifter that is on a
camshaft lobe is under pressure
of the valve springs; therefore
leak-down or escape of oil from
lifter l o w e r chamber occurs.
When the engine is started a few
seconds may be required to fill
the lifter, particularly in cold
weather when oil is sluggish. If
noise occurs from this cause only
occasionally it may be considered
normal and requiring no cor-
rection. If noise occurs almost
daily, however, check for: (a) Oil
too heavy for prevailing temper-
atures (par. 1-1) (b) Excessive
varnish in lifter.
(2) Intermittent Rapping Noise.
An intermittent rapping noise that
Appears and disappears every few
seconds indicates leakage at check
ball seat due to foreign particles,
varnish, or defective surface of
check ball or seat. Recondition
noisy lifters (par. 2-15) checking
carefully for presence of grit or
metal particles, which would re-
quire a thorough cleaning to re-
move source of such material.
(3) Noise on Idle and Low Speed.
If one or more valve lifters are
noisy on idle and up to approxi-
mately 25 MPH but quiet at higher
speeds, it indicates excessive
leak-down rate or faulty check
ball seat on plunger. With engine
idling, lifters with excessively
fast leak-down may be spotted by
pressing down on each rocker
arm above the push rod with equal
pressure. Recondition noisy lift-
ers (par. 2-16).
(4) Generally Noisy at All Speeds.
Check for high oil level in crank-
c a s e . See subparagraph b (1)
above. With engine idling, strike
each rocker arm above push rod
several sharp blows with rawhide
hammer; if noise disappears it
indicates that foreign material
was keeping check ball from seat-
ing. Stop engine and place lifters
on camshaft base circle. If there
is lash clearance in any valve
linkage it indicates a stuck lifter
plunger, worn lifter body lower
end, or worn camshaft lobe. Re-
condition noisy lifter (par. 2-16).
(5) Loud Noise at Normal Operat-
ing Temperature Only. If a lifter
develops a loud noise when engine
is at normal operating tempera^
ture but is quiet when engine is
below normal temperature it in-
dicates an excessively fast leak-
down rate or score marks on
lifter plunger. Recondition lifter
(par. 2-16).
2-11 ENGINE VIBRATION
OR NOISE
If unusual vibration or noise de-
velops in the operation of a car,
test first to determine whether
the condition originates in the
engine or in other operating units.
Time w i l l often be saved by
checking the recent history of the
car to find out whether the vibra-
tion or noise developed gradually
or became noticeable following an
accident or installation of repair
parts.
Vibration or noise is usually most
pronounced when driving at a cer-
tain speed. If the engine is run at
the equivalent or critical speed
with car standing and transmis-
sion in neutral, the condition will
still exist if the engine or trans-
mission is at fault. If the condi-
tion does not exist with engine
running and car standing still re-
fer to Rear Axle Trouble Diagno-
sis and C h a s s i s Suspension
Trouble Diagnosis.
If vibration or noise exists with
engine running and car standing
still, the following items should
be investigated and corrected as
required.
a. Engine Tune-Care
An engine which is not properly
tuned will run rough and vibrate,