Chery S11 / Chery QQ. Manual — part 241

Chery QQ Maintenance Manual 465 Engine Mechanical System

The following 4 factors shall be considered when you make diagnosis of engine noise:
● Classification of noise
● Conditions for noise to happen
● Frequency for noise to happen
● Position for noise to happen in the engine
Noise of engine is usually synchronous with engine speed or half of engine speed.You
should try to make sure frequency of the noise.
1 Main bearing noise
Noise results from main bearing damage or wear is just like the sound of knocking, it
happens once every circle that the engine rotate,the noise comes to maximum when the
engine works with heavy load,knock of interval knoking sound which is much more piercing
than the main bearing wear noise,shows that axial clearance of crankshafts is too big.
The following conditions can lead to main bearig noise:
● The pressure of oil pump is too low.

The oil is too thin or/and the oil filter is too dirty.
The clearance of main bearing is too big.
The end clearance of crankshaft is too big.
The shaft journal of crankshaft is out of round.
Belt tension is too high.
Crankshaft pulley is not tight enough.
Main bearing cover is not tight enough.
Driving belt pills.

2 Connecting rod bearing noise
Sound of knocking is generated at all speed under the condition of connecting rod bearing
being damaged or wear ,connecting rod noise and knocking sound of piston or looseness of
piston pin may be confused together easily in early stage of connecting rod bearing
damage,knocking sound of connecting rod will become louder along with engine speeding
up,this noise comes to maximum while decelerating.
The following circumstances can be the cause of noise:

Bearing clearance is too big.
Crankshaft connecting rod journal wear
The oil is too thin or/and oil filter is too dirty
Oil pressure is too low
The shaft journal of crankshaft connecting rod is out of round.
Connecting rod malposition
Connecting rod nut fixed torque is not correct
Bearing halfshell is not correct or bearing halfshell is malposition

3 Piston noise
It is hard to distinguish the noise generated by piston pin ,piston and connecting rod,loose
piston pin may result in sharp double knocking sound,usually,it can be heard when the
engine is idling or the engine speeds up suddenly then slow down;the piston pin will be
ticking slightly if the piston is installed not properly, the noise becomes more obvious if the
engine works without heavy load;too much clearance between piston and cylinder liner will
result in sound of knocking the cylinder from inside,this kind of noise is similar to metal

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Chery QQ Maintenance Manual 465 Engine Mechanical System

knocking sound,just like the piston slap the cylinder shell from inside during the process of
stroke. Engine noise slowing down after warming up is a sign for piston to slap
cylinder,there is too much clearance between piston and cylinder liner when the engine is
cold,sound of slaping is much louder.
The following circumstance can lead to piston noise:

Piston pin wear or looseness
Piston pin is installed not properly.
There are too much clearance between piston and cylinder liner.
Lubrication is not enough.
The carbon deposit at piston crown knocks cylinder head.
Piston ring groove wear or fracture
Piston fracture
Connecting rod malposition
Piston ring wear or damage
The clearance of piston ring groove is too big.
The clearance of piston ring ends is not enough.
Piston malposition is at a angle of 180 degree
The shape of piston skirt is not correct.

4 Flywheel noise
Check whether or not the flywheel is loose or fractural according to the following steps:
4.1 Drive the vehicle at the speed o f 32 km/h.
4.2 Turn off the engine
The flywheel may be loosened or damaged if you hear the kind of pinging sound,this kind of
pinging sound comes to maximum while decelerating.Bearing knocking sound can result
from looseness of bolts.It depends on stability of idling to generated how much slapping
sound when the engine is idling at high speed,the noise can be made or can not be made if
transmission drive put into gear.Check the connecting bolts between transmission and
flywheel, crankshaft and flywheel first,before make sure whether or not there is some
relationship between the knock and bearing.
5 Valve device noise
Valve device malfunction can be shown by means of slight slapping sound of any frequency
or frequency is equal to half of engine speed,the noise will go up along with acceleration of
the engine.
First,warm up the engine before judging the valve device noise,so as to make the engine
parts expand to normal state.Listen to engine noise under the circumstance of engine cover
being shut.
Remove the rocker arm head ,make sure the parts of valve device which result in noise with
stethoscope,if the noise of valve device is abnormal.The cause of noise are introduced as
follows:

Valve spring fracture, resiliency of valve spring is not enough.
Valve is blocked or curved
Rocker is curved
The cam of camshaft is damaged or poor performance.

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Chery QQ Maintenance Manual 465 Engine Mechanical System

Lubrication of valve device is not good or oil pressure is too low.
The clearance of valve stem and valve guide pipe is too big.
Valve guide pipe wear
Push rod wear
Valve rocker wear
Bolt of valve rocker fracture
Auxiliary parts of valve rocker is too loose or damaged.

3 Diagnosis of engine noise

1 Exhaust device

Symptom

Cause of malfunction/ Troubleshooting

Vibriation or quack
noise of exhaust
system

Looseness or malposition of exhaust parts,you can carry out the
following procedures:
1 Align the joints.
2 Fasten the joints.
3 Check to see whether or not exhaust lifting hook , mounting
bracket and clamp are damaged.

Waste gas leak or

noise

The following conditions can result in waste gas leak or noise:

Exhaust parts joints or connection leak.
Tighten clip or connecting parts to regulated torque.
Installation of exhaust system is not correct or malposition.
Align and tighten the clip.
There are some cracks on the exhaust manifold.
Leakage between exhaust manifolds or between the

cylinder heads.

Fasten the exhaust manifold on the cylinder head according

to the regulation

Tighten or replace exhaust manifold washer.
Exhaust expansion connection parts damage or wear.
Replace parts if necessary.
Exhaust pipe is burned or rusty.
Replace the exhaust pipe if necessary.
Sliencer is damaged or burned.
Replace the silencer assembly.
Exhaust clip and/or bracket are damaged or loosened.
Replace the parts if necessary.

2 Valve device

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Chery QQ Maintenance Manual 465 Engine Mechanical System

Symptom

Cause of malfunction/Troubleshooting

There is some noise while
idling,the noise becomes
lounder when the rotational
speed is much higher.

This kind of noise has nothing to do with malfunction
of tappet,it is becomes more obvious under low gear
speed of 10-15 km/h,this kind of noise sounds just
like ticktack,the following condition can result in this
kind of noise:

Valve end or Valve rocker gasket wear

Clearance of valve stem and valve guide is too
big.

Radil run-out of valve seat is too remarkable.

Radil run-out of valve working surface is too
remardable.

Malposition of valve spring

1 Rock the engine until the nosing valve depart from
the valve seat.
2 Rotate valve spring and valve
3 If the noise is corrected ,check the valve spring to
see whether or not it is in malposition. If the
malposition exceeds the limit,replace the valve spring.

Driving at high-speed ,there is
some noise,while driving at
low-speed,the noise disappear.

High-speed driving noise may result from the
following condition:
Oil level is too high.If oil level is higher than FULL
(full mark),crankshaft balancer will stir the oil into
foams,when the foam is pumped into the tappet,the
tappet will make noise.Make the oil being put in
correct oil level.
Oil level is too low.
If oil level is lower than ADD(add mark),the
atmosphere will be pumped in by oil pump,it will
result in tappet noise,add oil if necessary.

Oil pump filter screen is bent or too loosened.

Noise which has nothing to do
with engine speed.

Check the following circumstances:

Lubricating system of rocker.

Rocder ball wear.

Rocker is bent or damaged.

Valve rocker is too loosened or damaged.

3 Abnormal noise diagnosis of engine

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