Audi Workshop Service and Repair Manuals > A4 Cabriolet Mk2 > Power unit | 4-cylinder TDI unit injector engine (1.9 ltr.; 2.0 ltr. 2-valve), mechanics | Engine cylinder head, valve gear | Cylinder head | Checking compression

Checking compression - engine codes AVB, AVF and AWX

Special tools and workshop equipment required

t	U/J extension and socket, 10 mm -3220-

t	Compression tester -V.A.G 1763-

t	Adapter -V.A.G 1381/12-

Test conditions

l	Engine oil temperature at least 30 °C.

l	Battery voltage at least 12.5 V

Test sequence

–	Pull dipstick -1- out of guide tube.

–	Unclip cover caps.

–	Unscrew nuts -arrows- and detach engine cover panel.

–	Remove insulation beneath cover panel (if fitted).

–	Re-insert dipstick in guide tube.

–	Unplug electrical connector -2-.

–	Loosen bolt -3-.

–	Pull fuel filter upwards out of bracket and lay it aside with fuel hoses connected.

–	Turn knurled nut -1- for main connector anti-clockwise and unplug main connector.

–	Detach electrical connectors at glow plugs.

–	Unscrew all glow plugs using U/J extension and socket, 10 mm -3220-.

–	Screw in adapter -V.A.G 1381/12- in place of the glow plug in each cylinder.

–	Test the compression pressure with the compression tester -V.A.G 1763-.

Note

Using the compression tester → operating instructions.

–	Have a 2nd mechanic operate starter until tester shows no further pressure increase.

Compression pressure	bar
When new	25 … 31
Wear limit	19
Difference between cylinders	5 (maximum)

Installation is carried out in the reverse order; note the following:

–	Install glow plugs → Rep. Gr.28.

–	Interrogate and erase the fault memory for engine control unit, as faults are stored when the connectors are unplugged → Vehicle diagnosis, testing and information system VAS 5051.

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