Copyright by Goodheart-Willcox Co., Inc.
Chapter 23 Front End Service 513
Damper
driving tool
Figure 23-30. A special tool is required to install this press-fit
damper. (General Motors)
Holding
tool
Torque wrench
Crankshaft
snout bolt
Crankshaft
pulley
Figure 23-31. A special tool is recommended to hold the
vibration damper while torquing the crankshaft snout bolt.
and increase emissions. Check chain slack by turning the
crankshaft back and forth. If it can be turned excessively
without valve train movement, the chain is worn.
Timing sprockets with plastic gear teeth are a common
source of problems. The plastic teeth can wear or break off.
A bad chain tensioner can also cause excess chain slack.
To begin timing chain installation, check any keys
or dowel. Turn the crankshaft and camshaft to align the
timing marks. The timing marks on the sprockets must align.
Timing marks can be small dents, circles, or other figures
on the sprockets. The service manual will usually illustrate
them. Fit the chain and sprockets in place together.
Do not hammer on the outer edges of the sprockets
to force them into place. Use light blows in the center of
the sprockets.
Do not crank an engine with the starter motor with
the timing chain, belt, or gears removed. The pistons could
slide up and bend the valves.
An oil slinger fits in front of the crankshaft sprocket
to prevent oil leakage and to lubricate the timing chain or
gears. Make sure it is not installed backwards.
Inspect a timing belt for signs of deterioration. Most
manufacturers recommend timing belt replacement every
50,000 miles or 80,500 km. However, most mechanics
replace the belt whenever it is removed for service.
Install the timing belt as you would a timing chain.
Align the timing marks. The number one piston should usu-
ally be at TDC on the compression stroke when the marks
align. If the belt is reused, it should be installed to rotate in
the same direction as before.
Adjust timing belt tension to prevent belt breakage
or looseness. Special belt tension gauges are available.
However, you can adjust the belt until moderate finger
pressure is needed to twist the belt about one-quarter turn.
Timing gears are very dependable. However, gear
teeth can break and wear after extended service. During
timing gear service, measure gear backlash and runout
with a dial indicator.
When installing a new front oil seal, drive out the old
seal without damaging the front cover. Coat the outside
diameter of the new seal with nonhardening sealer. Wipe
engine oil on the inside of the seal. Drive the new seal in
squarely.
An engine front cover can be installed using a
conventional gasket, chemical sealants, or both. Use
extra silicone where two seals come together. Torque all
fasteners to specifications.
Review Questions—Chapter 23
Answer the following questions using the information
provided in this chapter.
1. Generally, if you can deflect a timing chain more than
_____ the chain should be replaced.
2. How can you check timing chain wear on an OHV
engine without removing the timing cover?
3. _____ must align to time the camshaft and valves with
the crankshaft and pistons.
4. Explain how to fit the timing chain and sprockets onto
the engine.
5. Which part of a chain tensioner should be inspected
for wear?
6. Why should you never crank an engine with the start-
ing motor when the timing chain or belt is removed?
7. This part keeps oil from spraying out the front seal and
helps lubricate the timing chain or gears.
(A) Tensioner.
(B) Shroud.
(C) Slinger.
(D) Front cover.
8. A timing belt is normally replaced at least every _____
miles.
9. If you do not have a belt tension gauge, how can you
adjust belt tension properly?