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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