1: When starting the car from cold, the engine compartment makes a chirping sound.
This may be because the belt is sliding on the generator and the strong friction and vibration between the belt and pulley produces a certain sound frequency. The main cause of belt slippage is belt loosening or aging. Factors that can cause belt play are incorrect belt tensioner adjustment or insufficient tensioner elasticity. First you need to adjust the tension of the belt tensioner. If it has no effect, replace it. the tensioner wheel. Belt aging mainly means that the belt gradually hardens, loses elasticity and reduces friction with the pulley during long-term use. How to confirm if the generator belt is making abnormal noise: Before starting, pour water on the generator belt, turn it on and the gasoil disappears. Within 1 or 2 minutes the water vapor dissipated and the scream reappeared. Pour a little more water and the abnormal sound disappears again. In this case, only the generator belt can be replaced.
Two: Abnormal noise when turning the steering wheel
If the steering wheel makes an abnormal noise after turning, first check whether the steering oil is normal and whether the Steering oil is too low. Too low a level will cause the steering pump to fail. Operates normally (except electric assistance), but emits an abnormal noise when adjusting the steering. Second, we know that this abnormal noise may be related to the shock absorber pressure bearing. Damage to the pressure bearing is closely linked to the working method. In the future, on the road, do not turn the steering wheel on the spot, try to turn after the vehicle has moved. If the vehicle is stopped, turn the steering wheel toward the center to ensure that the ssuspension and tires do not support the load. When it is necessary to turn around on the spot, some car owners often like to bump the steering wheel and always want to pass in a hurry. In fact, it is the most damaging to car parts. When the flat bearing is broken, it is easy to hear the squealing sound when turning the steering. Seriously affects people's mood while driving.
Three: There is a cracking sound coming from the chassis
When the car drives on uneven roads, the tires will swing up and down. That is to say, the A-arm swings, the tire is installed on the axle, and the axle head is connected to the A-arm through the ball joint. The A-arm is actually a universal joint. During active or passive steering, the vibrator compresses. The tripod is connected to the subframe via the hinge sleeve of the front connection point of the subframe set ithis. pass through The hinge sleeve of the front connection point of the subframe is transferred to the body, and the hinge sleeve of the front connection point of the subframe is likely to become a part prone to cracking, that is- i.e. the hinge sleeve position of the front connection point of the subframe in the event of an “off-axle” accident. Also known as the lower limb rubber sleeve, it is made of hard rubber connected to the chassis A-arm and plays a buffering role when crossing uneven roads. If broken, the tripod will impact the frame. Must be replaced. Remember that you can usually go to a 4S store to replace it separately, there is no need to replace the whole thing.
1. The relationship between abnormal noise and engine speed
The existence of the most common abnormal noises in engines depends on the speed conditionengine.
1. Abnormal noise only exists at idle or low speeds. The reasons for the noise are: the gap between the piston and the cylinder wall is too large; the piston pin is too tight or the connecting rod bearing is too tight; The gap between the tappet and its guide hole is too large; the profile of the valve cam is worn; sometimes the starter pawl is loose and the pulley makes noise (obviously when changing gears).
2. The sound is chaotic when maintaining a certain speed, and short-term sounds occur one after another during rapid deceleration. The reasons for the noise are: the camshaft timing gear is cracked or its fixing nut is loose; the crankshaft is broken; the piston pin bushing is loose; The camshaft axial play is too large or its bushing is loose.
3. Abnormal noise occurs when the engine accelerates quickly, and the son always exists when the engine is running at high speed. The reasons for the noise are: the connecting rod bearing is loose, the bushing is burned, or the size does not match and rotates; the crankshaft bearing is loose or the bushing is burned; broken.
2. The relationship between abnormal noise and load
Many abnormal noises on the motor are obviously linked to their load. During diagnosis, the method of unloading cylinders one by one can be changed. used for testing. Usually, the single or double cylinder ignition method relieves the load on one or two cylinders to identify the relationship between abnormal noise and load.
1. The fire in a certain cylinder is cut off and the abnormal noise disappears or is reduced. The reasons for this noise are: knocking of the piston on the cylinder; loose connecting rod bearing; leaking broken piston pin;
2. If the fire in a certain cylinder is cut off, the sound increasesera or there will be no sound at that time. The reasons for the noise are: the copper sleeve of the piston pin is loose; the conicity of the piston skirt is too great; the connecting rod bearing cover mounting bolts are too loose; or the connecting rod bearing is too loose; the alloy melted; The steering wheel mounting bolts are too loose.
3. The abnormal noise of two adjacent cylinders cutting the fire is reduced or disappears. The reasons for the noise are: a loose crankshaft bearing.
3. The relationship between abnormal sound and temperature
1. It makes noise at low temperature, when the temperature increases, the sound decreases or even disappears. The reasons for the noise are: the gap between the piston and the cylinder wall is too large; the piston is out of alignment due to the depth and width of the main bearing oil groove; the engine oil pressure is low and the llubrication is poor; .
2. There is a sound when the temperature increases, and the sound decreases or disappears when the temperature drops. Reasons for noise include: premature ignition caused by overheating; the long and short axes of the piston skirt ellipse are in opposite directions; the ovality of the piston is small and the gap between the piston and the cylinder wall is too small; is distorted; the gaps between the piston rings are too small.
4. The relationship between abnormal noise and engine duty cycle
Engine abnormal noise failures are often obviously related to the motor duty cycle, especially the crank rod mechanism and the crank mechanism. valve. the noises are all related to the work cycle. For a four-stroke engine, any noise caused by the crank rod mechanism is emitted twice once when the engine is operating; all sounds caused bythe valve mechanism are issued once when the engine is running;
1. Causes of abnormal noise caused by the crank-connecting rod mechanism include: the piston knocks against the cylinder wall; knocking noise from the piston pin and cylinder head; the bearing is too loose; the piston ring is leaking.
2. Causes of abnormal noise caused by the valve mechanism include: excessive valve clearance; excessive clearance between the lifter and its guide hole; broken valve spring; radially cracked camshaft timing gear; Valve seat ring loose and unable to close.
3. If the abnormal sound has nothing to do with the duty cycle, you need to pay attention to the area where it makes the sound. Usually, the noise caused by the gap which has nothing to do with the duty cycle is mainly a fault in the engine accessories; if there is a metallic friction noise continu coming from parts of the machine which has nothing to do with the work cycle, this can be considered that some rotating parts are defective.
5. The relationship between abnormal noise and engine parts
When the engine emits abnormal noise, it will inevitably produce a certain degree of vibration depending on the characteristics and location of the vibration. , it can help diagnose the cause of abnormal noise.