Audi A4, S4

since 2000 of release

Repair and car operation

Compression check in engine cylinders, identification of leaks

Compression check

The most admissible difference of pressure in separate cylinders can make 3.0 atm. (for diesel engines of 5.0 atm.).

Pressure of a compression grows in the serviceable engine very quickly. The low value shown after the first cycle, increasing with the subsequent cycles, indicates wear of piston rings. Low value after the first cycle, not increasing after the following, signals that or valves are not tight, or laying of a head of the block (the crack in a head can be the reason also) is punched. To decrease in a compression can lead deposit existence on plates of valves.

It is necessary to mean that because of different speed of rotation of a starter on different models the results received as a result of measurements can differ. The results received at measurement of a compression, should be approximately identical to all cylinders.

If pressure is in any cylinder at level minimum admissible and even below, for clarification of the reason execute to a trace yushchy actions. Pour in in the cylinder through an opening for a candle a teaspoon of impellent oil and repeat compression measurement.

If oil addition temporarily improved a compression, the reason of its decrease, most likely, is wear of the piston, rings or the cylinder. If the increase in a compression did not occur, it is possible to assume that the reason — in a leakage of valves or the punched laying of a head of the block.

Low compression in two next cylinders almost for certain — a consequence of breakdown of laying of a head. Availability of cooling liquid in chambers of combustion or in a case of the engine will confirm this assumption.

If the compression in one of cylinders approximately for 20 % is lower, than in the others, besides turns of idling are unstable, the reason, probably, excessive wear of a cam of a cam-shaft.

After completion of check establish to the place of a spark plug (address to Head the Current leaving and service, put on them tips of high-voltage wires, attach the socket to the ignition coil. Establish into place a plastic cover of the engine and a safety lock of the fuel pump.

Values of pressure of a compression for various engines are given in Specifications.

Petrol engine

PERFORMANCE ORDER

Switch off ignition. Engine of 1.6 l: Disunite the socket of a target step of the coil of ignition. The target step is in one case with ignition coils on the engine. Take out a safety lock No. 28 of the fuel pump. Engine of 1.8 l: Disunite sockets of coils of ignition and injectors. L engines 2.0, 2.4 and 3.0: Remove ignition coils. Disunite the socket of injectors. Remove all spark plugs, address to the Section Check and replacement of spark plugs. Check of a condition of high-voltage wires. At a provorachivaniye of the engine be not declined over the engine. There is a danger of a travmirovaniye owing to emission of particles of soot. Turn the engine a starter to remove a deposit and soot. Establish a check point in neutral situation and tighten the parking brake. Screw компрессиометр according to the guide of the manufacturer in an opening for a candle. Ask the assistant to press a pedal of gas and during check to hold her foot. Turn the engine approximately on 8 turns so that on компрессиометре any more there were no pressure throws. Consistently check all cylinders and compare the received values of pressure to the set. Establish to the place of a spark plug and fix them the moment 30Нм, address to the Section Check and replacement of spark plugs. Check of a condition of high-voltage wires. Again join all disunited sockets, if necessary, insert into place a safety lock.

At a rassoyedineniye of sockets in the control unit of the engine data on malfunctions register. It is recommended to remove as soon as possible the written-down data on HUNDRED AUDIS.

Diesel engines

PERFORMANCE ORDER

Engine of 1.9 l: Disunite the central tip of the engine. For this purpose turn to the left the screw with a notch. Disunite the socket of spark plugs. Engine of 2.5 l: Disunite the TNVD socket. Remove all glow plugs, address to the Section Removal and installation of candles of an incandescence. Screw компрессиометр with flexible accession instead of incandescence candles. The values of a compression specified in Specifications correspond to measurement with the help компрессометра to V.A.G. In case of use of other measuring devices deviations are possible. In this case it will be possible to measure only disorder of pressure on separate cylinders. Turn the engine approximately on 8 turns so that on компрессиометре any more there were no pressure throws. Establish to the place of a glow plug and fix them the moment 15Нм. Attach a wire. Join and fix all sockets.

At a rassoyedineniye of sockets in the control unit the engine data on malfunctions register. It is recommended to consider and remove the written-down data as soon as possible.

Check on leaks

During this check are defined speed of an exit from cylinders of the compressed air pumped in them and directly a place of leaks. This check is alternative to compression check. Moreover, from many points of view it is much more effective as visually to reveal a source of leak simpler, than to comprehend results of measurement of a compression.

The equipment, necessary dlyaproverka on leaks, does not belong to public therefore performance of this check should be entrusted specialists of the service center.