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If an abnormal noise (knocking)
that seems to be coming from the lash adjuster is heard
after starting the engine and dose not stop, carry out the
following check.
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2.Check that the noise
occurs immediately after the engine is started, and that the
noise changes in accordance with changes in the engine
speed. If the noise dose not occur immediately after the
engine is started, or if it dose not
change in accordance with the engine speed, the problem is
not being caused by the lash adjusters,
so check for some other cause of the problem. Moreover, if
the noise dose not change in accordance
with the engine speed, the cause of the problem is probably
not with the engine (In these cases,
the lash adjusters are normal).
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3.While the engine is
idling, check that the noise level doses not change when the
engine
load is varied (for example, by shifting from N to D). If
the noise level changes, the cause of the noise is probably
parts striking because
of worn crankshaft bearings or connecting rod bearings (In
such cases, the lash adjusters are
normal).
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4.After the engine has
warmed up, run it at idle and check if any noise can be
heard. If the noise has become smaller or disappeared,
oil sludge could make the lash adjusters
stick. Clean the lash adjusters (Refer to GROUP 11D -
Rocker Arms and Camshaft - Rocker
Arms and Camshaft Inspection ). If not
improved, go to
step 5.
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5.Bleed air from the lash
adjusters (Refer to ).
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6.If the noise has not
disappeared even after the air bleeding, clean the lash
adjusters
(Refer to, GROUP 11D - Rocker Arms and Camshaft
- Rocker Arms and Camshaft
Inspection ).
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1.Check the engine oil and
replenish or replace the oil if necessary.
note |
- If there is an only small amount of oil,
air will be drawn in through the oil
screen
and will get into the oil
passage.
- If the amount of oil is greater than
normal, then the oil will being mixed by
the
crankshaft and a large amount of air may
get mixed into the oil.
- If the oil is degenerated, air and oil
will not separate easily in oil, and the
amount of air mixed into the oil will
increase.
- If the air which has been mixed in with
the oil due to any of the above reasons
gets into the high pressure chamber of
the lash adjuster, the air inside the
high pressure chamber
will be compressed when the valve is
open and the lash adjuster will
over-compress, resulting in
abnormal noise when the valve close.
This is the same effect as if the valve
clearance is adjusted
to be too large by mistake. If the air
inside the lash adjusters is then
released, the operation
of the lash adjusters will return to
normal.
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2.Run the engine at idle for
1 - 3 minutes to let it warm up. 3.With no
load on the engine, repeat the drive pattern shown in the
illustration at
left and check if the abnormal noise disappears (The noise
should normally disappear after 10 - 30
repetitions, but if there is no change in the noise level
after 30 repetitions or more, the
problem is probably not due to air inside the lash
adjusters). 4.After the noise has disappeared,
repeat the drive pattern shown in the illustration
at left a further 5 times. 5.Run the engine at
idle for 1 - 3 minutes and check that the noise has
disappeared.
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