Audi 80/Avant (B4)

Too low pressure of compression

In regular intervals low pressure of compression not necessarily is a disturbing sign; the reason can be and measuring admissions of various control devices. However it is necessary to reflect, if between separate indicators of cylinders differences more than 2-3 bar are measured. It can mean:

• Deterioration of pistons and piston rings.
• Закоксовывание piston rings because of formation of adjournment.
• Development (эллипсность) in cylinders as consequence of jamming of pistons.
• Adjournment on cores or saddles of valves because of the combustion or oil rests.
• The burnt down valves. In most cases leaky adjoining valves are at the bottom of insufficient pressure of compression and, thereby, the lowered capacity of the engine. To help a trouble it is possible only major repairs of a head of the block of cylinders.

Search of malfunctions

More precisely to define malfunction at low pressure of compression (a low compression), it is necessary to apply the following cunning: to drip in an aperture for a spark plug it is a little oil from a butterdish and once again to measure pressure.

• If indicators still low, the reason – valves.
• If you have received higher indicators the reason are piston rings or, probably, as well cylinders. The added oil has created for short time the best consolidation between pistons and walls of cylinders so the compressed gas could not disappear therefrom almost.

The test of system for tightness

More exact results can be received after system check on tightness which some workshops can spend. For this purpose compressed air direct to the combustion chamber through apertures of spark plugs.

If the checked chamber of combustion loses pressure, it can be seen on a scale of the control device. Rather big place of leak can be distinguished listening:

• Blares near a branch pipe of an exhaust pipe specify in the leaky final valve.
• If air leaves the case of the air filter, means, the inlet valve is faulty.
• In case of a defective lining of the block of cylinders or a crack in a head of the block of cylinders the compressed air comes to light from the next aperture of a spark plug or from an open broad tank with a cooling liquid.
• The worn out walls of cylinders, mirrors of cylinders or piston rings pass air in картер, whence it leaves through open branch pipes for наливания oils or on directing tube oil probeа.