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.