Copyright by Goodheart-Willcox Co., Inc.
Chapter 23 Front End Service 505
Figure 23-10. Make sure the oil slinger is installed in the
correct orientation.
Double-check
that key is
in place
Inspect the rubbing
block for wear
Tensioner spring
assembly
Timing chain
Figure 23-9. Inspect the chain tensioner closely before
installation. The fiber rubbing block can wear. Refer to wear
specifications. (Ford)
Caution: On some overhead camshaft
engines, do not use the starter motor to
turn the crankshaft with the timing chain or
belt removed. It is possible, in some designs, for the
pistons to hit the valves. The valves could be bent.
On these engines, turn the camshaft and crankshaft
very slowly by hand to avoid part damage.
Installing a Chain Tensioner
A chain tensioner is used in most OHC timing chain
mechanisms. Inspect it closely, Figure 23-9. The fiber
rubbing block can wear off. Replace it if needed.
Fit the tensioner onto the engine. Then, pull on the
chain to make sure the tensioner moves properly. Some
plunger-type tensioners can bind if worn and extended
too much.
Installing an Oil Slinger
The oil slinger fits in front of the crankshaft sprocket.
Look at Figure 23-10. It slings oil out of the chain and also
prevents front seal leakage. This is usually a trouble-free
part. However, if bent or damaged, it should be straight-
ened or replaced.
Make sure the slinger faces the correct direction. If
installed backward, it can rub on the front cover. This
mistake would require front cover removal, a time-
consuming procedure. Then, slide the slinger over the
crankshaft snout.
Timing Belt Service
Many OHC engines use a synthetic rubber timing belt
to operate the engine camshaft. The cogged (square-toothed)
belt provides an accurate, quiet, light, and dependable
means of turning the camshaft, Figure 23-11. Timing belt
service is very important. If the timing belt breaks or is
improperly installed, engine valves, pistons, and other
parts could be damaged.
Inspecting the Timing Belt Mechanism
Most manufacturers recommend belt replacement
about every 50,000 miles (80,500 km). The timing belts
on some late-model engines are designed to last the life of
the engine without adjustment or replacement. However,
the timing belt should be replaced if oil or coolant has
contaminated the belt. Refer to the owner’s manual or ser-
vice manual for belt service intervals if in doubt.
The timing belt is normally replaced during major
engine repairs. Since timing belt removal can be very time-
consuming, most technicians replace the belt whenever it
is removed, regardless of how long the belt has been in
service. Timing belts are relatively inexpensive.
During timing belt service, inspect not only the belt,
but the sprockets, tensioner, and other parts for problems.
Inspect the timing sprockets for rounded teeth or physical
damage. Spin the tensioner wheel by hand to check for
a bad bearing. See Figure 23-12. The wheel should spin
freely and quietly. Replace the tensioner bearing if you can
feel any roughness. Since timing belt tensioners are sealed,
many technicians like to replace a tensioner whenever
the front end is disassembled, especially on high-mileage
engines.
Look for oil leaks that will allow oil onto the timing
belt. These must be fixed. Oil will cause rapid failure of
the timing belt.