Crankshaft

Check the crankshaft journals for scoring. Any noticeable roughness indicates the need for regrinding or replacement of the crankshaft.

If the crankshaft has been reground, check for burrs around the holes for lubrication channels. Discovered needle files, remove burrs or scraper and thoroughly clean the holes and channels on the chip.

Micrometer, measure the diameter of the main and connecting rod crankshaft journals and compare the results with the technical data. Cervical measure at several points, both in diameter and length, it will reveal the roundness and taper.

Check the contact surface with sealing sleeves at both ends of the crankshaft to wear and other damage. If the cervix is in contact with the cuff has considerable wear may require replacement of the crankshaft.

Wear crankpins characterized metal knock arising while the engine is under load at low speed, and a decrease in oil pressure.

Worn crankshaft main journals characterized by a strong vibration motor and a hollow metallic thud, increases with increasing engine speed, as well as a decrease in oil pressure.

With overhaul of the engine, even if the main and connecting rod bearings to be replaced, they still need to be examined carefully. In their defects can be judged on the technical condition of the engine.

Bearings can fail due to lack of lubrication, dirt and foreign particles, motor overload or corrosion. Reasons caused by bearing failures, it is necessary to eliminate before the engine will be assembled again.

To inspect the bearings, remove and place them in the same order in which they were installed on the engine. This will determine the proper crankshaft and facilitate troubleshooting.

Foreign particles can get into the engine in different ways. The metallic particles appear in the engine oil as a result of engine wear. The fine particles together with the engine oil can get into the bearings and easily integrate into their soft metal. Larger particles entering into the bearing, can cause scratches on it or on the crankshaft. To prevent failure of the bearing for this reason, it is necessary to thoroughly clean all of the internal surfaces of the engine and keeping them clean during assembly. It is recommended to comply with the prescribed by the oil change intervals and oil filter.

Insufficient lubrication on the crankshaft journals can be caused by many factors: high oil temperature, motor overload, oil leakage, etc.

The manner of driving also affects the bearing life. At full throttle at low engine speed of the engine increases the load on the bearings and there is squeezing the oil film from the contact zone. High loads lead to cracks in the working part of the bearing, which in turn can cause separation of the antifriction layer of the steel substrate.

Short trips lead to corrosion of the bearings due to the fact that the engine reaches stable operating temperature at which water is removed from the crankcase vapors and gases corrosivity. Fumes and gases condense in the engine oil, acid and form a precipitate. Acid together with engine oil enters the bearings and cause corrosion.

Wrong choice of bearings in the engine assembly also causes the release of their failure. The bearings mounted with an interference fit, is not sufficient clearance to ensure proper lubrication of the rubbing surfaces.

When installing the crankshaft, consider the following.

Persistent half rings 11 and 14 (Fig. 3.4.36) installed only on the fourth main bearing and are used to adjust the axial clearance of the crankshaft.

Oil grooves persistent half rings must be directed outward.

The insert 12 without the oil groove is set by the bearing cap.

When assembling the bearing cap bolts must be replaced with new ones.

Bolts main bearing caps tighten in the sequence shown in Fig. 3.4.38 in five stages:

Stage 1 - 1-8 tighten bolts to 60 Nm;

Stage 2 - tighten bolts 1-8 at 90 ?�;

3rd stage - 9-16 tighten bolts to 60 Nm;

Step 4 - tighten the screws 9-16 at an angle of 90 ?�;

Stage 5 - tighten the bolts A to 28 Nm

Measurement of axial and radial clearance Crankshaft

Replace the engine block bracket with a dial indicator so that the measuring tip of the indicator rests on the counterweight of the crankshaft (Fig. 3.4.39).

Move along the axis of the crankshaft in one direction until it stops and place the arrow on the dial indicator to 0. Move along the axis of the crankshaft in the opposite direction up to the stop and fix the value shown indicator. The nominal value of the axial clearance of the crankshaft is 0,090-0,251 mm, the maximum allowable amount - 0.280 mm.

To measure the radial clearance in the bearings of the crankshaft using a calibrated plastic rod Plastigage.

Unscrew the bolts and remove the main bearing cap and insert the root. Clean the insert cover and the crankshaft.

Cut a piece of plastic calibrated rod length is equal to the width of the bearing and place it along the axis of the crankshaft main bearing on the neck.

Install the bearing cap with the insert and fix its bolts, having tightened their moment of 30 Nm. This does not turn the crankshaft.

Unscrew the screws and remove the back cover of the radical bearing. Compare the width of the deformed plastic core with a measuring scale on the packaging of the plastic rod. On a scale determine the radial clearance. The nominal value of the radial clearance Crankshaft 0,018-0,045 mm, the maximum allowable amount - 0.10 mm.