Checking Pressure Loss On The Engine

Information 

• The check for loss of pressure can be used to assess the mechanical condition of a combustion engine. 
• pressure loss test is more meaningful than the compression pressure check. 
• The percentage leakage quantity can be used to determine whether the leaks in the combustion chamber in question are so large that the combustion chamber must be repaired. 
• The worn components (e.g. piston rings) can be identified by the compressed air that is escaping. 

Information 

The piston must be exactly at the upper return point when checking pressure loss. Do not touch any components of the belt drive and do not put any tools on the crankshaft pulley while performing the check.

Information 

The pictures shown in this document may differ from the original.

Information 

Read the work steps and tips in the attached operating instructions before starting the pressure loss test. The device described here is used as an example for all suitable pressure loss testers. Details of calibration and use can be found in the relevant operating instructions.

1. Get the tester ready. NEW  : > VAS 522 001 - Pressure loss tester  /OLD:  > VAS 522 001 - Pressure loss tester 
2. Screw the test hose into the spark plug thread of cylinder 1 by hand (compression TDC) and tighten hand-tight.

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   Test hose 

3. Connect the pressure loss tester to the compressed air system.
4. Adjust the scale. To do this, insert the test nozzle at the front into the device.

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   Adjusting scale 

5. Turn the adjusting wheel until the scale pointer is at the "cal." marking or "23%". The pressure is then equal in the two test chambers of the tool.

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   Adjusting wheel 

6. Remove test nozzle and check that the pointer falls back. Then connect the test hose. The value that is displayed should not be greater than 25%. If the pressure loss is greater, it is safe to assume that the engine needs an overhaul.

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   Pressure loss test 

7. Interrupt the compressed air supply and unscrew the test hose.
8. Check the next cylinder by turning the crankshaft through another 90° and check the next cylinder in the firing order following the instructions provided.

   V6 firing order: 1 - 4 - 3 - 6 - 2 - 5 

   V8 firing order: 1 - 3 - 7 - 2 - 6 - 5 - 4 - 8