Troubleshooting: Remove the left front wheel cylinder for inspection. The floating pin is free from bending and dryness, and no abnormality is found in other parts. After replacing the left front wheel brake cylinder, the fault no longer appears, indicating that the piston of the left front wheel brake cylinder is stuck when the stroke reaches the maximum in the case of emergency braking. Lead to the above failure phenomenon. Step on the brake a few more times, and the piston will return to the normal position, and the fault will be eliminated.
The air conditioner does not cool.
Fault phenomenon: the air conditioner of Lefeng new car has no refrigeration function.
Fault detection and analysis: found in trial operation. After pressing the AC switch and the internal circulation switch of the air conditioner, the switch indicator light does not light up, the air conditioner does not work, and the blower works normally. Check the circuit diagram and find out the answer. After the air conditioning switch of the air conditioner is turned on, the air conditioning request signal is sent to the engine control module. After that, ECM judges whether the air conditioning working conditions are met according to other signals, and then controls whether the compressor works through the air conditioning compressor relay. However, the power supply and grounding of the air conditioner internal circulation actuator are provided by the air conditioner control switch.
Using TECH2 to check the air conditioning request signal in the engine data sheet, it is found that the engine still cannot receive the air conditioning request signal after pressing the air conditioning switch. Possible reasons are: (1) air conditioning control switch failure; (2) The power of the air conditioning control switch is turned on.
After the air conditioner control switch was removed, it was checked with a multimeter. It was found that the grounding of the control switch was normal, but the power supply of plugs A 1 and A 10 was dead. These two power supplies are provided by the instrument panel fuse box. Check whether the wiring is normal, and the analysis is likely to be an internal fault of the instrument panel fuse box.
Troubleshooting: Troubleshoot after replacing the instrument panel fuse box.
Abnormal sound
Fault symptom: Chevrolet Lefeng mileage is 3 198km. When turning to the right and driving with the air valve, the front will make a creaking sound similar to belt slipping.
Fault detection and analysis: during trial operation, it was found that the original position and direction did not ring, and neither did the hoist. Check whether there are interference points between the engine and the gear train and power train at the front of the car body. Replacing the drive belt and tensioner is invalid.
So as to completely eliminate the possibility of abnormal noise generated by the power steering system. We removed the drive belt. Abnormal sound still appears in the test results. Let another technician lie prone on the powertrain, listen carefully while driving, and find that the abnormal noise comes from the transmission part. Because the abnormal noise only appears when driving to the right, it is likely to be caused by the friction between the differential or the differential and the axle shaft, but the axle shafts on both sides should be removed and carefully checked. No signs of abnormal wear were found, so it is invalid to replace the half shafts on both sides.
So I decided to disassemble the transmission and check the differential, and found nothing unusual. Because the sound comes from between the engine and the transmission, when checking the starter, it is found that the transmission mechanism of the starter is very loose, and the overspeed clutch and pinion can move freely on the shaft (see figure), resulting in centrifugal force when turning right. Overdrive clutch and pinion are thrown at the flywheel. The pinion interferes with the flywheel gear ring, causing abnormal sound. Then it bounces back, and so on, making a "squeak" sound similar to belt slipping.
Troubleshooting: After replacing the starter. Troubleshooting.
Chevrolet new scenery engine is noisy.
Fault symptoms: a Chevrolet new scenery with a mileage of 27052km, the customer complained that the engine was noisy.
Detection and analysis: during the test run, it was found that the whole body was shaking and ears were numb when the engine speed dropped, but there was no abnormal sound when listening carefully to the engine. According to the empirical analysis, the high-frequency vibration of the engine may be transmitted to the car body, and the possible reasons are as follows: (1) The added engine lower protective steel plate is deformed and stuck to the engine exhaust pipe. The vibration of the engine is transmitted to the engine through the exhaust pipe; (2) The damping capacity of the feet connected between the engine and the vehicle body is invalid.
Troubleshooting: Replace the feet on the engine side and conduct trial operation. Troubleshooting.
The engine temperature of Chevrolet Cruze is high when driving.
Fault symptom: The mileage of a Cruze is 356km, and the engine temperature is too high when driving.
Fault detection and analysis: It is found that there is no antifreeze in the antifreeze storage tank. After adding antifreeze, the car was hit, and no leakage point was found in the external cooling system of the engine. The radiator fan was normal at low speed. However, after running for a period of time, it was found that the liquid level of antifreeze dropped again, and the oil level and oil quality of engine oil and automatic transmission lubricating oil were normal, which ruled out the possibility that antifreeze entered the lubricating system in series through the lubricating oil cooler. There are two possibilities for analysis: (1) water leakage in the heater water tank (see figure); (2) There are sand holes or cylinder pads in the engine. Causes antifreeze to leak into the combustion chamber and be discharged out of the car through the exhaust system.
After opening the driver's pedal pad, I found that there was a lot of red antifreeze in it, and the heater tank was above the center console. After removing the center console trim panel, it was found that the heater tank leaked near the pipe joint.
Troubleshooting: replace the warm air water tank and add antifreeze to troubleshoot.
It's noisy in the Chevrolet copaci.
Fault symptom: A copaci, with mileage of 1805 1km, was complained by the customer that the noise inside the car was high.
Detection and analysis: During the test run, it was found that the noise of "buzzing ……" could be heard in the car when the engine was running. Put your ear to the car and listen carefully. It is found that the noise near the taillight is the loudest, and it is suspected that it may be the abnormal noise generated by the fuel pump. Copaci oil tank adopts high-density polyethylene, because the center passes through the transmission shaft and exhaust pipe, and the oil tank can only be designed as a saddle, so there are two oil pumps inside the oil tank, one is the electric main oil pump on the left. One is the mechanical auxiliary oil pump on the right (pictured).
In order to determine which oil pump produced abnormal noise, the ignition switch was turned on after the flameout, and the electric fuel pump worked for 2 s, resulting in little noise, indicating that it was not the abnormal noise produced by the electric fuel pump. After hitting the car, lift the car and listen with a stethoscope. After comparison, it is determined that the abnormal sound is generated by the right auxiliary oil pump. The analysis may be the liquid flow noise generated when the auxiliary oil pump pumps fuel.
Troubleshooting: After replacing the new auxiliary oil pump, the noise disappears and the fault is eliminated.