Chevrolet 1988 Light Duty Truck Repair Manual page 373

Make sure that the keepers seat properly in
the groove.
Repeat the preceding steps on the rem aining
valves.
Check each valve seal using J 22330. Wet the
suction cup portion of the tool lightly with
engine oil. Place the suction cup over the
valve stem cover and push the tool down to
create a vacuum. If the vacuum remains at the
tool, the seal is properly installed. If a vacuum
cannot be obtained, or if the seal will not hold
a vacuum , it may have been dam aged or
im properly installed.
M easu re
* Valve spring installed height.
— Use a narrow, thin scale. A cutaway scale may
be helpful.
— Measure from the valve shim or spring seat to
the top of the valve cap.
— If this measurement exceeds the figure given
in " S pecifications," install valve spring seat
shim s of su fficie n t th ickn e ss (between the
spring and cylinder head) to give the desired
m easurement. Never shim the spring to give
an installed height under the specified figure.
THERMOSTAT AND HOUSING
The therm ostat is located in a housing bolted to the
front of the cylinder head.
A therm ostat consists of a restriction valve controlled by
a therm ostatic element. The restriction valve cranks or
just starts to open at a predeterm ined tem perature and
continues to open as the engine coolant tem perature
increases. To assure proper cooling and engine warm-up
it is im portant that the correct therm ostat be used. Refer
to the p ro per Truck S ervice M anual for the correct
therm ostat application.
D isassem b le (F ig u re 3)
1. Bolts (8 and 9).
2. Water outlet (10).
3. Therm ostat (12).
4. Gasket (11).
In sp e ct (F ig u re 3)
Water outlet (10) and housing (13) for cracks or
damage.
*
A ssem b le (F ig u re 3)
1. Therm ostat (12).
2. Gasket (11).
3. W ater outlet (10).
4. Bolts (8 and 9).
&
T ig h te n
Bolts (8 and 9) to 23 N m (17 ft. lbs.).
2.5 LITER L4 ENGINE 6A1-21
CRANKSHAFT AND BEARINGS
C lean (F ig u re 5)
Crankshaft (88) with solvent.
— Do not scratch the bearing journals.
— Blow all sludge from the oil passages with
com pressed air.
Main bearinq inserts. W ipe free of oil with a soft
cloth.
i?
In sp ect (F ig u re 5)
C rankshaft (88) for cracks. Use the m ag naflux
method, if available.
C ra n k p in s , m ain b e a rin g jo u rn a ls and th ru s t
surfaces for scoring, nicks, or dam age caused by
lack of lubrication.
Main bearing inserts (86 and 72) for scoring or other
damage.
In g eneral, the lower inse rts (except the #1
bearing) show a greater wear and the most distress
from fatigue. If, upon inspection, the lower insert is
suitable for use, it can be assumed that the upper
insert is also satisfactory. If the lower insert shows
evidence of wear or damage, both upper and lower
inserts must be replaced.
C rankshaft gear (87) for chipped or damaged teeth.
M easu re (F ig u res 37 and 38)
Main bearing and connecting rod journal diameters.
Compare with " S pecifications" at the end of this
section.
Because the 2.5 L engine crankshaft is of the
rolled fillet type, the crankshaft cannot be reground.
If the measurements do not meet the specifications,
replace the crankshaft.
Main bearing and connecting rod journals for taper
and out of round. If the journals are tapered or out of
ro u n d m o re th a n 0 .0 0 0 5 -in c h ,
crankshaft.
C rankshaft runout.
re p la c e th e