Tune-Up Information; Use Of Rtv Sealer And Anaerobic Gasket Eliminator; Replacing Engine Gaskets - GMC G Service Manual

6A-2 ENGINE. PBIVEABILITY AND DIAGNOSIS
understood that proper cleaning and protection of
machined surfaces and friction areas is part of the
repair procedure. This is considered standard shop
practice even if not specifically stated.
• On diesel engines, whenever the fuel injection pump
or lines are removed or disconnected, care must be
taken to prevent the entry of dirt into the pump, lines,
and injectors. The entry of even small amount of dirt
or other foreign material into the fuel injection system
may cause serious damage.
• It should be kept in mind, while working on the
engine, that the 12-volt electrical system is capable of
violent and damaging short circuits. When performing
any work where electrical terminals could possibly be
grounded, the ground cable of the battery should be
disconnected at the battery.
• Battery cables should be disconnected before any
major work is performed on the engine. Failure to
disconnect cables may result in damage to wire har­
ness or other electrical parts.
• Cover or otherwise protect exposed electrical con­
nections to prevent damage from oil and fuel.
• When raising or supporting the engine for any reason,
do not use a jack under the oil pan. Due to the small
clearance between the oil pan and the oil pump
screen, jacking against the oil pan may cause it to be
bent against the pump screen resulting in a damaged
oil pickup unit.

TUNE-UP INFORMATION

All information required to tune up the vehicle's engine is
given in the Engine Emission Control Label. This label is
located in the engine compartment.
Information that can be found on the label includes:
• Spark plug type and gap.
• Ignition timing.
• Valve lash (if applicable).
• Idle, fast idle, and solenoid screw speeds, as
applicable.
• The proper sequence for making the adjustments.
• Emission hose routing diagram (sometimes on a sep­
arate label).
USE OF RTV SEALER AND
ANAEROBIC GASKET ELIMINATOR
Two types of sealer are commonly used in engines cov­
ered by this manual. These are RTV sealer and anaerobic
"gasket eliminator" sealer.
It is important that these sealers be applied properly and
in the proper place to prevent oil leaks. THE TWO TYPES
OF SEALER ARE NOT INTERCHANGEABLE. Use the
sealer recommended in the procedure.
• RTV (room temperature vulcanizing) sealer is used
where a non-rigid part is assembled to a rigid part.
Common examples are oil pans and rocker arm
covers.
• Anaerobic gasket eliminator hardens in the absence
of air. This sealer is used where two rigid parts (such
as castings) are assembled together. When two rigid
parts are disassembled and no sealer or gasket is
readily noticeable, the parts were probably assem­
bled using gasket eliminator.
USING RTV SEALER
1. Don't use RTV when extreme temperatures are
expected, such as exhaust manifold, head gasket or
where gasket eliminator is specified.
2. When separating components sealed with RTV, use
a rubber mallet and "bump" the part sideways to
shear the RTV sealer. "Bumping" should be done at
bends or reinforced areas to prevent distortion of
parts. RTV is weaker in shear (lateral) strength than
in tensile (vertical) strength.
Attempting to pry or pull components apart may
result in damage to the part.
3. Surfaces to be resealed must be clean and dry.
Remove all traces of oil and RTV. Clean with a chlori­
nated solvent such as carburetor spray cleaner. Don't
use petroleum cleaners such as mineral spirits; they
leave a film onto which RTV won't stick.
4. Apply RTV to one of the clean surfaces. Use a bead
size as specified in the procedure. Run the bead to
the inside of any bolt holes. Do not allow the sealer in
any blind threaded holes, as it may prevent the bolt
from seating properly or cause damage when the bolt
is tightened.
5. Assemble while RTV is still wet (within 3 minutes).
Don't wait for RTV to skin over.
6. Torque bolts to specifications. Don't over-torque.
USING ANAEROBIC GASKET ELIMINATOR
1. Clean surfaces to be resealed with a chlorinated sol­
vent to remove all oil, grease and old material.
2. Apply a continuous bead of gasket eliminator to one
flange.
3. Spread bead evenly with your finger to get a uniform
coating on the complete flange.
4. Assemble parts in the normal manner and torque to
specifications.

REPLACING ENGINE GASKETS

CAUTION: Composite type gaskets are used in
some areas of the engine assembly. These gas­
kets have a thin metal core. Use caution when
removing or handling composite gaskets to help
avoid personal injury.