Peugeot 308: Check : Pressure, engine end of compression - Measuring of the leak rate of the cylinders
ESSENTIAL : Observe the safety and cleanliness recommendations
.
ESSENTIAL : All personnel carrying out work on a vehicle fitted with traction batteries must have received specific electric vehicle training and be authorised to work on these vehicles (observe the regulations in force in the respective country).
1. Tooling
Workshop equipment :
- Compression tester for petrol engines
- plug spanner
| Tool | Reference | Description |
| [01100][EN-35667-A] | Leakage tester |
2. Measuring the pressures at the end of compression
CAUTION : Checking is carried out with the engine cold.
Deactivate the fuel pump ; Using the diagnostic tool.
Remove the spark plugs
.
Check that the engine’s speed of rotation, powered by the starter motor, is greater than 250 rpm.
Checks :
- Place the end of compression measurement unit on the base of the spark plug of cylinder No.1
- Keep pressure on the end of compression measurement unit
- Operate the starter
- Check that an end of compression measurement has been taken
- Note the value
- Reset the measurement unit
Proceed in the same way for the other cylinders.
N.B. : Compare the values obtained with those in the table
.
CAUTION : Look for the origin of the fault if there is an appreciable difference between the measured values.
Refit the sparking plugs
.
CAUTION : Observe the tightening torques.
Activate the fuel pump ; Using the diagnostic tool.
Read and clear the fault codes using the diagnostic equipment.
3. Measuring of the leak rate of the cylinders
3.1. Checking principle
After measuring the end of compression pressures, an additional examination is necessary to determine any sealing faults on one or more cylinders.
The cylinder is subjected to a compressed air pressure and the pressure gauge graduated from 0 to 100 % then indicates the rate of sealing of this cylinder.
3.2. Fitting the sealing checking equipment
Preparation before taking the measurement :
- Refer to the equipment’s instructions to check its calibration
- Remove the spark plugs
Disconnect connector of the cylinder (1) reference sensor
(Exhaust side ) (at "a").
Remove :
- The bolt (2)
- Cylinder reference sensor (1) (Exhaust side )
"A" : The piston of cylinder number 1 is at top dead centre : The valves are closed.
"B" : The piston of cylinder number 1 is at bottom dead centre : The valves are open.
Check position "b" or "c" of the target through the cylinder reference sensor (1) hole (Exhaust side ).
N.B. : The target of the cylinder reference sensor (1) is used to determine the opening or closing of the valves ; Position "c" of the target indicates that the camshaft is offset by 180°.
N.B. : Carry out a complete crankshaft revolution to bring the exhaust camshaft target into position (at "b") if the exhaust camshaft target is offset (at "c").
N.B. : The piston (3) of the cylinder number 1 being checked must be brought exactly to top dead centre and the end of compression (The position of the cams (4) indicates which cylinder is compressed).
Position "b" of the cylinder reference sensor (1) target, exhaust side, is used to determine the position of the cams (4).
Insert a metal rod (welding rod type) into the spark plug hole of cylinder number 1 (Coupling side).
Slowly rotate the crankshaft clockwise to position cylinder number 1 exactly at top dead centre.
N.B. : As soon as top dead centre is exceeded, even very slightly, slightly turn the crankshaft in one direction and then in the other direction to accurately determine top dead centre.
3.3. Measuring of the leak rate of the cylinders
Tighten the hose union of the tool [01100 / EN-35667-A] in the hole of spark plug number 1 (Flywheel side).
Assemble the hose on the tool [01100 / EN-35667-A].
Read the loss of compression shown as a percentage on the tool [01100 / EN-35667-A].
Turn the crankshaft by 240° using the bolt (5) and bring the piston of cylinder number 3 to top dead centre.
When the piston (6) of cylinder number 3 is at top dead centre, tighten the hose union of the tool [01100 / EN-35667-A] in the spark plug hole of cylinder number 3 (The position of the cams (7) indicates which cylinder is compressed).
Read the loss of compression shown as a percentage on the tool [01100 / EN-35667-A].
Turn the crankshaft by 240° using the bolt (5) and bring the piston of cylinder number 2 to top dead centre.
When the piston (8) of cylinder number 2 is at top dead centre, tighten the hose union of the tool [01100 / EN-35667-A] in the spark plug hole of cylinder number 2 (The position of the cams (9) indicates which cylinder is compressed).
Read the loss of compression shown as a percentage on the tool [01100 / EN-35667-A].
N.B. : Compare the values obtained with those in the table
.
4. Use of the results
4.1. Locations and causes
| Location of the origin of the noise | Possible causes |
| Air filterMotorised throttle housingIntake pipes | Inlet valve seats/inlet valves assembly cloggedDamage to the inlet valve seats |
| Exhaust manifold | Exhaust valve seats/exhaust valves assembly cloggedDamage to the exhaust valve seats |
| Oil filler cap on cylinder head coverOil gauge well | PistonPiston rings |
| Expansion tank | Cylinder head gasketCylinder head |
4.2. Piston ring leaks
Place a little engine oil in the cylinder via the spark plug well (Temporary elimination of piston/rings sealing faults).
If the loss of sealing is significantly less : The piston and the rings are not sealed.
N.B. : As the air pressure drives out the oil in a few moments, the leak detected previously returns to its initial value.
CAUTION : Identical values on the 3 cylinders checked and higher than those indicated are a sign of incomplete running in.
Peugeot 308 2021-2025 (P5) Service Manual
Actual pages
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