Mistakes in the use of grease
1 Grease filling of universal joint cross shaft
It is clearly stipulated in the general vehicle maintenance manual that the key teeth and intermediate bearings of the telescopic shaft sleeve are lubricated with calcium base, the needle roller bearings of the cross axle and the intermediate bearings of the rear axle drive vehicle are lubricated with gear oil. But in the actual work, because there is no filling equipment, some repairmen mistakenly lubricate the cross axle needle roller bearing with calcium base grease for convenience, resulting in a large number of cross axle bearing premature damage. Due to the universal joint of the cross shaft gear oil nozzle is a very common grease nozzle, often give people a misunderstanding, the fact that the grease is not filling needle roller bearing. Because of the high viscosity of the grease, when the grease gun through the nozzle to the internal cavity of the cross shaft grease, grease into the narrow oil channel resistance is very large, at this time the grease by pressure will be opened on the opposite side of the nozzle pressure relief valve and overflow, when the repairman mistakenly have to fill the bearing with oil. Therefore, gear oil pressure gun should be used to fill the gear oil.
2Apply grease to installation of cylinder cushions
Some repairmen like to put a layer of butter on the cylinder liner when they install it, thinking that this will increase the engine seal. But it is not helpful, it is harmful. The cylinder pad is an important sealing element between the engine cylinder block and the cylinder head. It not only must strictly seal the high temperature and high pressure gas in the cylinder, but also seal the cooling water and oil through the cylinder head and the cylinder block. If grease is applied to the cylinder head, part of the grease will be squeezed into the cylinder channel or oil channel when the cylinder head bolt is tightened. Under the influence of high temperature, some of the grease left on the cylinder liner will flow into the cylinder and burn off, while the other part will burn up into carbon deposit on the joint surface of the cylinder block and cylinder head, causing engine leakage. Therefore, do not apply grease when installing cylinder pads.
3Apply grease to tire bolts or nuts
In order to tighten the nuts easily and prevent corrosion, many repairmen apply grease to the tire bolts and nuts. Actually, this is the wrong way to do it. According to the mechanical principle, the screw thread has the characteristic of self-locking after the nut is tightened. This is because the screw Angle of the screw thread is smaller than the equivalent friction Angle between the threads. In the set bolt connection, the helix Angle is a certain value, while the equivalent friction Angle varies with the friction state between threads. Obviously, the equivalent friction Angle between threads decreases after oiling, and the self-locking performance of the bolt connection deteriorates. Therefore, do not apply grease to the bolts and nuts of the tire to prevent looseness of the coupling and loss of the tire.
4 Make the grease thin by adding lubricating oil
When some repairmen use grease in winter, they prefer to dilute it by adding lubricating oil. This is wrong. As the structure of grease is a colloidal structure system composed of thickeners and base oils, the thickeners form a structural network, and the base oils (generally ordinary lubricating oils) are absorbed into the network to form a stable structural system, ensuring that the thickeners and base oils will not separate. If the grease is added later, although it is stirred, it cannot be evenly dispersed and included in the network, so it is easy to be separated and lost in use, which is not conducive to lubrication. If you need grease with low consistency in winter, you can use no. 1 or No. 2 calcium base grease with small size.