Testing Cylinders For Leaks

NOTE: Numbers in parentheses ( ) indicate a component or tool in the associated illustration.

1. Warm up engine up to normal operating temperature (about 80oC)

WARNING
^ Risk of scalding as a result of hot coolant spraying out
^ Do not open the cap of the expansion reservoir or radiator unless the coolant temperature is below 90°C.
^ Carefully turn cap to the first detent or slowly about 1/2 turn.
^ Wear protective clothing.

2. Open cap of expansion tank or radiator (2)
- Turn 2-state cap half a turn anti-clockwise to release pressure.
- Then, unscrew cap (2).
3. Remove injection nozzles (18), refer to Powertrain Management.
4. Position piston of cylinder to be tested to ignition TDC
5. Connect cylinder leakdown tester (04) as follows:





A. Cylinder head cover installed
1. Screw long connector (01) with the right-angled connection piece (02) into the prechamber of the cylinder to be tested.
2. Calibrate cylinder leakdown tester and screw connection hose (03) of the tester onto the connection piece (02).





B. Cylinder head cover or camshaft housing removed
1. Screw short connector (04) with the angled connection piece (02) into the prechamber of the cylinder to be tested.
2. Calibrate cylinder leakdown tester and screw connection hose (03) of the tester onto the connection piece (02).





6. Pressurize cylinder with compressed air and read off pressure loss on tester (04)
- Leakdown test permissible loss.
Total Loss: ≤25%
Loss at head gasket and valves: ≤10%
Loss at pistons and piston rings: ≤20%

NOTE: If crankshaft rotates, install retaining lock for crankshaft/ring gear, refer to Installing/Removing Crankshaft Retaining Lock.

- If excessive pressure loss is noted, determine cause as follows:
If a high pressure loss was found with the cylinder leakdown tester, check the engine by listening at the cylinder head gasket, air intake area, exhaust, oil filler opening and prechamber of the adjacent cylinder(s).

Check the coolant in the coolant expansion tank for the presence of vapor bubbles.

Possible causes for the pressure loss are in the case of:
a. Air outlet through the prechamber or spark plug hole of the adjacent cylinder(s), vapor bubbles in the coolant expansion tank:
Pressure loss at cylinder head gasket.
b. Air outlet through the air intake area:
Pressure loss at inlet valve(s)
c. Air outlet through the exhaust:
Pressure loss at exhaust valve(s)
d. Air outlet through oil filler opening:
Pressure loss through pistons and piston rings

NOTE:
^ It is possible to localize the pressure loss of the appropriate cylinder by spraying in engine oil. Engine oil briefly seals off the gap between piston and cylinder.
^ If a reduced pressure loss now briefly occurs, the cause is most likely to be at the pistons, piston rings or cylinder wall of the relevant cylinder.

Firing Order Of The Series 606.xxx Diesel Engine:

7. Perform the test of the other cylinders in the firing order of the engine
8. Install in the reverse order