WM, 101802 Checking Pressure Loss Of Cylinders: Information
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- The test does not show any meaningful result on a new engine (i.e. one that hasn't been run in).
- A difference in pressure loss between the individual cylinders of approx. 5% is not significant.
- If the test shows an excessive loss of pressure (> 30%), a few drops of oil can be sprayed into the combustion chamber. Then repeat the test. If the loss in pressure is now significantly less, the seal between the piston and cylinder is damaged.
- The air that is escaping causes hissing noises, which indicate the component that is responsible for the loss of pressure.
If the limit values are exceeded, the engine must be started and the test repeated.
| Potentially faulty component | Location of noise |
|---|---|
| Pistons, piston rings, cylinder liner | Oil filler neck, positive crankcase ventilation |
| Cylinder-head gasket, cylinder head | Coolant reservoir |
| Outlet valve | Exhaust system |
| Intake valve | Intake system |