FORD SCORPIO

1985-1994 of release

Repair and car operation

3.2.3.7. Check and restoration of pistons and piston rings

THE GENERAL DATA

Deterioration of pistons and piston rings can be found out at occurrence of signs of the raised expense of oil and a low compression that is sometimes connected with deterioration of cylinders.

Other sign of deterioration of the piston is the knock of the piston similar to noise from outside of a cranked shaft which needs to be distinguished from knock of bearings. It is possible to listen to it accurately on small turns of the engine in the absence of loading (for example, in an idling mode), and it is audible much less at increase of turns of the engine. Deterioration of the piston usually arises around a skirt or the bottom end face of the piston. Considerably also, where the thickness of a skirt differs from the normal.

Backlash check in the lock of a piston ring with the help щупа


For check of deterioration of piston rings to remove rings from the piston, to insert rings into cylinders from above, having pushed them downwards approximately on 40 mm by means of the piston (from which rings have been removed). Then to measure a backlash in locks of rings with the help щупа for measurement of backlashes. If the backlash exceeds the specified maximum, rings require replacement.

In due course flutes in which rings on the piston settle down, also can increase in sizes.

However seldom happens that the piston has worn out only in flutes of rings, and the requirement for replacement on one only to this reason hardly can arise. At any replacement of pistons the weight of four complete sets of pistons and rods should be identical to keep the general balancing of the engine.

PERFORMANCE ORDER

1. For removal of piston rings cautiously to shift them to the top part of the piston so that not to scratch an aluminium alloy; never to shift them to a piston skirt. Piston rings are easy for damaging if to remove them carelessly, therefore this operation is necessary for carrying out extremely cautiously. It is possible to take advantage old щупами. 2. To raise one of edges of a piston ring which is necessary for taking from a flute, and to insert under it щуп. 3. Slowly to lead round щуп round the piston and when the ring leaves the flute, to remove it upwards, and щуп will keep it from соскальзывания in an empty flute if that already is available. 4. Piston rings should be removed always at the top the piston. 5. To check up that flutes for piston the end the pure. 6. The most simple way of installation of rings is use щупа, and installation of rings is made on one, since bottom маслосъемного rings. Then щуп it is possible to move downwards over other flutes of piston rings until the necessary flute will be reached. Then the piston ring moves with щупа in the necessary flute. 7. Other method of installation of rings is their deduction big and index fingers. Such method demands strong hands and the big care as the ring can be opened too strongly and to break.