4.2.13. Survey of assembly of pistons with rods


1. Before survey process assembly has to be cleared, and piston rings have to be removed.

2. Carefully remove old rings at the top of the piston. For prevention of sticking of rings in flutes it is possible to use old edges of shchupovy measuring instruments. Be careful, do not scratch the surface of the piston the ends of rings. Rings are made of very fragile material and at too strong expansion can break.

3. Besides about rings it is easy to be cut. Take care of protection of your hands and fingers. Pay attention that the 3rd piston ring has a dilator. Always remove rings only at the top of the piston. You store each set of rings together with the piston in case the set is repeatedly established.

4. Scratch out traces of a coal deposit from the top part of the piston. After removal of the main layer of a deposit it is possible to use a manual wire brush (or a piece of a thin emery paper).
5. By means of a fragment of an old piston ring remove a coal deposit from piston flutes. Be careful - you watch scratching out only coal deposits and not to scratch out metal of which the piston is manufactured. Also try not to scratch and not to form notches on side surfaces of glossy flutes.
6. After removal of coal deposits smooth out assembly of the piston with a rod by means of kerosene or other suitable solvent and carefully dry it. Make sure that maslovozvratny openings in ring flutes of the piston are well cleaned.
7. If pistons and mirrors of cylinders are not damaged and not strongly worn-out and if the block of cylinders does not demand a pro-point, then old pistons can be installed into place. Normal wear of the piston is usually visible as equal vertical strips on the persistent surfaces of the piston. At the same time there is a small weak point of the top piston ring in its flute.
8. Carefully examine each piston regarding detection of cracks around openings of a piston finger, and also on the surfaces of the piston between flutes.
9. Check whether there are no scratches and a protertost on a skirt of the piston, openings in the bottom of the piston and areas of a progar at the edges of the bottom. In the presence of zadir and wear of a skirt of the piston it is possible to assume that the engine often was exposed to an overheat and/or the wrong combustion was the reason of the excessive engine of high working temperatures. It is necessary to check carefully lubrication systems and coolings of the engine. Overheat traces on the side surfaces of pistons specify on being available for gases along a piston wall. Openings in the bottom of the piston or area of a progar at the edges of the bottom indicate that the wrong combustion (premature ignition or a detonation) took place. At detection above the specified problems it is necessary to define their reasons and to correct a situation, otherwise damages will arise again. Incorrectly exposed corner of an advancing of ignition and/or the wrong composition of air-fuel mix can appear the reasons.
10. Formation of pointed corrosion on the surface of the piston indicates a cooler leakage in the combustion chamber and/or in a case. The cause has to be besides removed, otherwise the problem will arise on the restored engine again.
11. If replacement of pistons is necessary, new pistons have to be bought in representative office of SAAB.
12. Carefully examine each rod regarding detection of signs of damage, such as scratches around the lower head and the top head of a rod. Make sure that the rod is not bent and is not twisted. Damages such are very little probable unless before there was a jamming or a strong overheat of the engine. Detailed check of assembly of rods can be made only in representative office of SAAB or in a workshop on repair of engines which have the necessary equipment at the order.
13. In pistons of this model of the car the piston fingers of floating type fixed on the places by means of two ring clips are established. Pistons and rods can be divided as follows.

14. By means of the small screw-driver with a flat sting remove ring clips.
15. Push out a piston finger. For removal of a piston finger will be pressing of a hand enough. Mark pistons, piston fingers and rods for the subsequent their assembly in former structure.
16. Examine piston fingers and bearings of the top head of a rod regarding detection of wear or damage. With wear is subject to replacement, both a finger, and the plug. However replacement of the plug is the procedure which has to be done by experts - existence of a press and extreme accuracy in work for this purpose is required.
17. Rods do not need replacement unless there were jammings or other strong mechanical damage. Visually examine whether rods are bent, in case of detection of a bend it is necessary to provide a rod for survey to specialists in capital repairs of the engine for more detailed check.
18. Make sure available all components of assemblies of pistons with rods, including also SAAB which are again acquired in representation. In case new pistons were bought, then they have to be sold complete with piston fingers and ring clips. Ring clips can be also acquired separately.
19. Install the piston so that the notch on the edge of the bottom was turned towards a distributive chain on the engine. And figures on rods and covers of bearings of the lower heads of rods were turned into the final party of the block of cylinders. If to hold pistons with a hand so that the notch was turned to the left, then number on a rod has to be turned to you. Oil a piston finger pure motive. Pass a finger through the piston and the top head of a rod. Make sure that the finger is in the piston and a rod an easy fit, then fix it by ring clips. Make sure that each ring clip correctly sat down in the flute.
20. Measure diameters of pistons and make sure that they correspond to diameters of the corresponding cylinders. In case the gap between the piston and a mirror of the cylinder is too big, the block has to be subjected to boring and in it new pistons and new piston rings have to be installed.
21. Check whether the interfaced surfaces of covers of the lower heads of a rod were exposed to processing by a file in wrong attempt to correct wear of bearings. Holding such procedure is extremely undesirable, and at detection of its traces rods and covers of bearings of the lower heads of rods have to be replaced.