Thermostat And Housing; Crankshaft And Bearings - GMC 1989 Light Duty Truck Repair Manual

Make sure that the keepers seat properly in
the groove.
Repeat the preceding steps on the remaining
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
improperly installed.
M easure
» 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 " Specifications," install valve spring seat
shims of sufficient thickness (between the
spring and cylinder head) to give the desired
measurement. Never shim the spring to give
an installed height under the specified figure.

THERMOSTAT AND HOUSING

The thermostat 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 predetermined temperature and
continues to open as the engine coolant temperature
increases. To assure proper cooling and engine warm-up
it is important that the correct therm ostat be used. Refer
to the proper Truck Service M anual for the correct
therm ostat application.
D isassem ble (Figure 3)
1. Bolts (8 and 9).
2. Water outlet (10).
3. Thermostat (12).
4. Gasket (11).
Inspect (Figure 3)
13
Water outlet (10) and housing (13) for cracks or
damage.
*
A ssem ble (Figure 3)
1. Thermostat (12).
2. Gasket (11).
3. Water outlet (10).
4. Bolts (8 and 9).
£
Tighten
Bolts (8 and 9) to 23 N m (17 ft. lbs.).
2.5 LITER L4 ENGINE 6A1-21

CRANKSHAFT AND BEARINGS

Clean (Figure 5)
— Crankshaft (88) with solvent.
— Do not scratch the bearing journals.
— Blow all sludge from the oil passages with
compressed air.
— Main bearing inserts. Wipe free of oil with a soft
cloth.
Inspect (Figure 5)
13
C rankshaft (88) for cracks. Use the m agnaflux
method, if available.
C ra n kp in s , m ain b e a rin g jo u rn a ls and th ru s t
surfaces for scoring, nicks, or damage caused by
lack of lubrication.
Main bearing inserts (86 and 72) for scoring or other
damage.
In general, the lower inserts (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.
Crankshaft gear (87) for chipped or damaged teeth.
M easure (Figures 37 and 38)
Main bearing and connecting rod journal diameters.
Compare with " Specifications" 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 ore th a n
crankshaft.
Crankshaft runout.
0 .0 0 0 5 -in c h , re p la c e th e