Chery A15. Manual - part 246

1. Basic description 
The cylinder combustion pressure leakage test provides a proper way to judge the 
working conditions of the engine cylinder.  
What can be discovered by way of cylinder combustion pressure leakage test includes: 

•  Exhaust and intake valve leakage 

•  Water leakage into adjacent cylinder or water pipeline 
•  Any other troubles caused by combustion/under combustion pressure 

Caution: do not take off the pressure cover on the left of the engine when the system is 
heated up as hot water may cause severe scalds.  
2. Checking steps 

•  Start the engine until it reaches the normal working temperature and then stop the 

engine.  

•  Clean the spark plug hole with compressed air  
•  Take out the spark plug 

•  Take out engine oil filter cover 

•  Take out compressed air filter 
•  Compare the test records with the ex-works data 

•  The minimum and maximum compression pressure for maintenance shall be 483KPA 

(70PSI) and 1,379KPA (200PSI) respectively. 522KPA (80PSI) is recommended.  

•  Test each cylinder as per the instructions provided by the manufacturer. When any 

leakage of compressed air from the throttle, exhaust pipe and engine oil filler cap is 
heard, please check relevant system problem.  

The pressures shall be evenly distributed. No cylinder shall have more than 25% of air 
leaked.  
For example: if the cylinder is filled with a pressure of 552KPA (80PSI), then the 
cylinder pressure shall maintain a minimum pressure of 414KPA (60PSI).  
3. Troubleshooting – cylinder cover gasket 
There will be leakage in the cylinder cover gasket between adjacent cylinders or water 
pipes.  
The possible problems which may be caused by the leakage between cylinders include:  
Decreased engine power 
Engine flameout 
 
 
 
 
 
 
 
 
 
 
 
 
 
Higher fuel cost 

 

The problems which may be caused by leakage of cylinders and water pipes include: 
Overheated engine 
Reduced cooling water 
Too much steam (while smoke) in the exhaust system 
Air in the cooling water 
4. Sealing test of adjacent cylinders 
In order to identify the leakage between adjacent cylinders, a test may be carried out as 
per the cylinder combustion pressure. A pressure reduction of 50%-70% will take place 
in the case of leakage between adjacent cylinders.  
5. Leakage test of cylinders and water pipes 
Caution: pay attention to the way of taking off the cooling water cover 
When the engine is cooled, take off the cooling water cover, start the engine until the 
thermostat is turned on. If there is any reduction in compression pressure, there will be 
cooling water in the water pipeline.  
How to test the cooling system 
Caution: the pressure rises rapidly where the cooling system is measured. There will be 
overpressure with the engine operation. So the pressure must be relieved. The maximum 
allowable pressure is 138KPA (20PSI). 
Fix cooling system checker or other equivalent tool, start the engine and observe the 
measured value. If the values of a cylinder fluctuate, then there must be air leakage in that 
cylinder.  
Chemical test method 
Use a chemical equipment to check the cooling system. Please refer to the Instructions 
Manual for the testing procedure.  
 
 
Five. Troubleshooting on impact noise 
Similar noises may originate from different parts. So check the following items:  
(1) Over or under oil level 
(2) When reinstalling the cylinder cover, run the engine at low speed for about 1 hour, 
failing which noise may take place.  
(3) During this period, stop the engine for several minutes and restart the engine to heat 
up the engine to the normal working temperature. Repeat the above steps.  
 
 
 
 
 
 
 
 
 
 
 
 
(4) Under engine oil pressure 

 

(5) Cylinder gasket leakage 
(6) Air leakage into the engine oil will damage the engine oil pump vanes.  
(7) Overused valve conduit 
(8) Overused rocker arm shaft 
(9) Loosened rocker arm shaft 
(10) Tappet failure 
 
 
Six. Troubleshooting on engine oil leakage 
The steps are as follows:  
(1) Do not clean or remove the engine oil smears at this moment as it can temporarily 
stop the leakage caused by swollen rubber seals.  
(2) Increase the solubility of the engine oil (recommended by the manufacturer), run the 
engine for 15 minutes and check the engine oil with an oil dipstick. The engine oil must 
be bright yellow under illumination. Run for another 15 minutes and check again. The 
engine oil must be in a bright color.  
(3) Check the quantity of candle powder in the engine with a light, especially where 
leakage is suspected. If any oil leakage is discovered, repair immediately.  
(4) If no candle powder is detected, drive the car at different speeds for about 15 minutes 
and recheck. 
(5) If the source of leaked oil can not be found, continue to check for engine oil leakage 
as follows:  
Remove the PVC valve off the cylinder cover and block the PVC valve. Fix a vacuum 
gauge on the vacuum pipeline and adjust the engine oil dipstick.  
Note: do not test with a pressure bigger than 20.6kpa (3 PSI).  
Gradually increase the air pressure from 1 to 2.5 PSI. When checking the suspected 
leakage with soap water, adjust the air pressure as appropriate to achieve the ideal effect 
and find the tiny leakage source. Please refer to the Maintenance Manual if any leakage is 
discovered. If the leakage occurs around the rear oil seal of the crank shaft, please refer to 
the chapters regarding rear oil seal checking.  
(6) If no leakage is found, shut off the high-pressure air supply, remove the air chamber, 
plugs and covers and fix the PVC valve and new air chamber and follow the following 
steps:  
 
 
 
 
 
 
 
 
 
 
 
 

 

(7) Clean any suspected oil leakage with an appropriate solvent. Start the car for about 15 
minutes and check the oil leakage with an illuminating light.  
 
 
Seven. Checking rear oil seal leakage 
Sometimes more complicated checking is required when it is difficult to identify the 
source of engine oil leakage. The following steps may help to find tiny leakage sources.  
If the leakage is located around the rear oil seal of the crank shaft: 
(1) Disconnect the storage battery 
(2) Jack up the car 
(3) Unfix the clutch cover and check if the rear body suffers any leakage with an 
illuminating light.  
If any leakage is found around the rear oil seal, then unfix the gearbox and check more 
carefully.  
(A) Foggy engine oil keeps spraying out, which indicates damaged oil seal or crank shaft; 
(B) Decrease in leaked air indicates multiple holes in the cylinder body or reduced 
precision of the cylinder body surface.  
(4) If no leakage is found, then seal the crank case and check for any oil leakage.  
Note: the pressure shall not exceed 20.6kPa (3 psi). 
(5) If no leakage is discovered, slowly rotate the crank shaft and look for any leakage. 
When any leakage is discovered between the crank shaft and oil seal, 

the crank shaft oil 

seal may have been damaged.

  

Note: please carefully check the crank shaft surface and sealing flange.  
(6) Please disassemble the engine for overhaul and more detailed checking.  
(7) After the engine leakage source has been identified, replace the damaged component 
assembly if necessary.  
 
 
Eight. Troubleshooting on damaged or worn-out parts 
Maintenance methods for damaged or worn-out parts (excluding spark plugs and 
camshaft main bearing cover) 
Damage or worn-out parts may be repaired (not excluding spark plug and camshaft main 
bearing cover). Fix or unfix with special tools so that the original dimension may be 
achieved.  
Electrical tools can be used for easy installation.