Determine loss of pressure at cylinder - AH01.00-N-1300-02A

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All engines

If an increased pressure loss was found with the cylinder leaktightness tester, inspect engine by listening at cylinder head gasket, air intake area, exhaust, oil filler opening and prechamber or spark plug bores of the adjacent cylinder or cylinders. Check the coolant in the coolant expansion reservoir for the formation of air bubbles.

Possible causes for the pressure loss are:

Outlet of air through prechamber or spark plug bore of adjacent cylinder or cylinders, air bubbles in coolant expansion reservoir:
pressure loss at cylinder head gasket
Outlet of air through air intake area: For inspecting by listening, open throttle valve pressure loss at inlet valve(s)
Outlet of air through exhaust:
pressure loss at exhaust valve(s)
Outlet of air through oil filler opening:
pressure loss through pistons and piston rings

It is possible to pinpoint the pressure loss of the relevant cylinder by spraying with engine oil. Engine oil seals off the gap between piston and cylinder briefly.

If a reduced pressure loss now occurs for a short time, the cause is very likely to be at the pistons, piston rings or cylinder contact surface of the relevant cylinder.

Determining the cause can be falsified by the position of the piston ring joints. If suspicion exists that the loss of pressure is caused by the piston ring joints being positioned directly one above the other, fit parts to engine and repeat test after running engine for a short time.