In automobile maintenance operations, we often encounter a variety of problems, such as engine high temperature, gearbox shift stop, vehicle running deviation, pneumatic chassis lifting and so on. However, some failures are not the fault of the parts themselves, but related to the maintenance habits of the maintenance personnel.
Today I will share a case of Porsche Cayenne assembly failure, the cause of which is related to the torque of assembly fixing screws. In the assembly of other parts of the automobile, fixed screws have specified torque and Angle
The material and installation position of the parts are different, and the torque of the parts fixed by screws with the same specifications will be different. But to be clear, the tightening of the bolt is not the greater the torque, the better.
In this case, the air-reduction model is fitted to the 2010-2017 Porsche Cayenne and the new Touareg (2011-2018) models of GM and Volkswagen
According to the customer's report, the original factory left front wheel gas reduction inspection to determine the leakage, replace the new shock absorption loading, the car parked for a period of time, the left front wheel obviously sank, after replacing the new distribution valve and air pump, the fault is still not solved.
It indicates that there is a fault in the new shock absorber. Remove the left front air damper for pumping leakage test, and it is found that bubbles emerge at the position of the pressure retaining valve, as shown in the figure below:
The factory will be unified quality inspection before leaving the factory, there will be no pressure valve leakage failure. Therefore, other aspects need to be analyzed
The reasons for pressure retaining valve leakage can be roughly divided into three categories:
1. The rubber ring of the pressure retaining valve is damaged
2. the pressure retaining valve is not fixed in place
3. Failure to operate according to assembly specifications
Try to remove the pressure retaining valve, it is found that the twisting shape of the pressure retaining valve is abnormal and it cannot be removed smoothly. After forcibly removing the valve, it is found that the thread of the pressure retaining valve and the thread of the end of the air bag appear slip-wire, as shown in the figure below:
Normal pressure retaining valve diagram:
This situation may be caused by the failure to operate in accordance with the specifications. Normally fastened bolts will not damage the thread. It should be that maintenance personnel use too much force when assembling the gas pipe, leading to the rotation of the pressure retaining valve at the bottom, causing the thread damage; It is also possible that the thread was not aligned during assembly
Correct installation specification: When assembling the gas pipe, the bolts should be tightened according to the torque requirements of the main engine factory, and the thread alignment should be checked.
Conclusion: When fastening bolts, it is not better to use more force, but should refer to the maintenance manual and the requirements of the main engine factory. Excessive fastening bolts will lead to abnormal damage of parts and components.
