3.12. There were extraneous knocks

Fig. 3.1. Zones of listening of knocks in the engine: 1 – radical bearings; 2 – connecting rod bearings; 3 – piston fingers; 4 – pistons; 5 – valves

If it seemed to you that at engine work there were sounds which was not earlier, be immediately convinced, whether all is perfectly in order with the engine. More often knocks in the engine are connected with serious malfunctions, for diagnosing and which elimination it is necessary to assort the engine in the conditions of service or garage. However it is possible to try to define independently the reason of knocks to decide – to go on car-care centre under the own steam or on a tow.

THE PREVENTION If you have the slightest doubts in independent diagnostics, get a towing cable. Serious repair of the damaged engine will cost more expensive, than tower services.

Knock of radical bearings – very dangerous; the motor to stop immediately, on car-care centre or it is necessary to go to garage on a tow. Knock of low tone. It is listened in the bottom part crankcase, considerably amplifies under loading and at increase in frequency of rotation. Its occurrence is frequent is accompanied by oil pressure drop (the lamp of pressure drop of oil burns almost constantly).

Knock шатунных bearings – very dangerous; the motor to stop immediately, on car-care centre or to garage to go on a tow. A sound rhythmical, sonorous, metal, average tone. Considerably increases at increase in loading and completely vanishes at spark plug switching-off.

Knock of piston fingers – dangerous; without loading the engine, it is possible to reach on car-care centre or in garage independently. Rhythmical, a high-pitch tone with a sharp metal shade, it is audible on all power setting and amplifies at increase in loading at the engine. Completely vanishes at spark plug switching-off.

Knock of the worn out pistons and cylinders – harmless; without loading strongly the engine, it is possible to reach on car-care centre or in garage independently. A sound reminding knock of pottery. It is especially well audible on not heated-up engine, in process of warming up decreases or disappears.

– harmless, it is possible to reach knock of valves on car-care centre or in garage independently. Metal knock against the general deaf noise. It is well listened on small and average frequency of rotation of a cranked shaft from outside heads of cylinders over the locations of valves. Knock of valves usually appears at failure of hydrojacks with which in this case it is necessary to replace.

Detonation knocks – dangerous, but, as a rule, are eliminated by replacement of the gauge of a detonation. Without loading strongly the engine, it is possible to reach on car-care centre or in garage independently. The sonorous metal knocks arising, as a rule, at dispersal of the car. The reason – refusal of the gauge of a detonation, application low-octane fuel, an engine overload at too early inclusion of the raised transfer, considerable carbonization in combustion chambers. It is necessary to replace the detonation gauge (section 9 "Electric equipment" see) and to apply a special additive to fuel to deposit removal on valves and in combustion chambers.

At occurrence of extraneous knocks in a suspension bracket of the moving car it is necessary to establish at once their source irrespective of, constant it is knock or appears only at journey of roughnesses.

THE PREVENTION Malfunctions in a suspension bracket and a car steering can lead to serious failure!

GOOD ADVICE To check a condition of a suspension bracket it is better, having put the car on a platform, a viewing ditch or the lift and if such possibility is not present, it is possible to do this work and on a free equal platform, though and with smaller conveniences. In any case the assistant is required to you.

Begin check with attentive survey of a condition of details of a suspension bracket.

1. Check up a condition резинометаллических hinges bottom...	2.... And the top levers of a forward suspension bracket...

3.... Rubber plugs of a bar of the stabilizer and reliability of their fastening скоб.	4. Attentively examine suspension bracket levers. Cracks and mechanical damages of levers, especially in places of fastening of spherical hinges, are inadmissible.

5. Check up reliability of fastening and a condition of the top pillow and...	6.... The bottom fastening of lobbies and...

7.... Back shock-absorbers. Replace pillows and plugs with the rubber torn, cracked or squeezed out on the one hand.	8. Check up deterioration of spherical hinges...

9.... And support of a forward suspension bracket.

10. For check of hinges raise a forward wheel a jack (or will hang out the car on the lift, having established under the bottom lever a support and having lowered the car a little to unload hinges).

11. Shake a wheel in a vertical plane, and the assistant should press a brake pedal to exclude possible люфт in nave bearings. If it is felt люфт (the top external edge brake скобы moves more than on 0,5 mm; it is possible to measure this distance, for example, by means of the indicator), means, hinges are worn out, at journey of roughnesses they can publish knock and it is necessary to replace them.

12. Shake a wheel in a vertical plane, undertaken one hand top, and another for a wheel bottom at the released pedal of a brake. The raised knock from outside the central part of a wheel testifies to the big backlash in the nave bearing.

13. At check of a back suspension bracket will pay attention to a condition of bearings of naves, shock-absorbers, springs, longitudinal and cross-section bars and fastenings of rods of shock-absorbers to a body. Attentively examine an arm of a cross-section bar of the back bridge on a body.

GOOD ADVICE After replacement of separate details of a forward suspension bracket it is necessary to check up and adjust corners of installation of forward wheels necessarily. This operation needs to be spent at the special stand in the conditions of car-care centre as wrong installation of wheels leads to the raised deterioration of tyres, increase in the expense of fuel and deterioration of stability and controllability of the car. Pay attention to system of release of the fulfilled gases. Very often owing to application of non-standard elements or breakage of elements of a suspension bracket of the muffler it can be a source of strong knock, especially at перегазовках. For check stop the engine, examine attentively release system, check up reliability of fastening and a suspension bracket of the muffler. Undertaken the end of an exhaust pipe, shake the muffler upwards-downwards and here and there – knocks should not be.

To diagnose serviceability карданной transfers on noise published by it it is difficult enough. If you did not manage to define precisely a noise source, address to the qualified expert.

To diagnose serviceability of the back bridge on noise published by it it is difficult enough. If you did not manage to define precisely a noise source, address to the qualified expert.

To diagnose serviceability of the forward bridge on noise published by it it is difficult enough. If you did not manage to define precisely a noise source, address to the qualified expert.

Malfunctions not only suspension brackets, but also a car steering can be the reason of knocks from below.

THE PREVENTION The steering condition substantially influences not only convenience of driving, but also on traffic safety.

Preliminary estimate a steering condition on a free wheeling of a steering wheel which should be no more than 5 ° (17 mm on a steering wheel rim).

The bad condition of spherical hinges of steering draughts, the pendular lever and the steering mechanism, condition of wheels and spherical hinges of a forward suspension bracket can be the reason of knocks and vibrations on a steering wheel. For steering check put the car on a horizontal platform and do following operations.

1. Sharply turning a steering wheel in both directions (it the assistant should do), check up visually and on hearing fastening of the pendular lever...	2.... And the steering mechanism (movings on bolts of fastening and knocks are not supposed)...

THE PREVENTION If the case of the steering mechanism and the pendular lever move here and there, it is necessary to tighten their fastening to a frame.

3.... Axial люфт in hinges of tips of steering draughts...

THE PREVENTION Tip of steering draught with the damaged cover of the hinge or the raised backlash in the hinge necessarily replace new. At replacement of tips of steering draughts probably infringement of corners of a convergence of wheels.

4.... Reliability of an inhaling and latching of nuts of fingers of spherical hinges.	5. Under the panel of devices check up reliability of an inhaling of a nut of a coupling bolt of fastening of the hinge of an intermediate shaft of a steering column to a shaft of the steering mechanism.

6. Attentively examine tyres of forward wheels. Strong blows from a road surface, especially at hit in hollows, can cause stratification of threads of a cord in a skeleton of the tyre and occurrence of camber ("hernia") or a tyre warp.

GOOD ADVICE The disbalance of forward wheels can be the possible reason of vibration and blows on a steering wheel at movement with a speed above 70–80 km/h. Address on car-care centre or point of mounting for check of balancing of forward wheels. If blows and vibration on a steering wheel appear at the moment of pressing a brake pedal, replacement brake колодок, repair or replacement of forward brake disks (section 8 «Brake system» see) is necessary.