Some small concrete mixer drivers reported that the same mixer they bought at the same time with their friends will have engine problems after using their vehicles for a period of time, but their friends' vehicle engines are all right. What's the matter? Let's have a look.
1. Improper application of maintenance data of mixer truck
The failure to scientifically select maintenance data in the maintenance of mixer truck is an important reason for the early damage of mechanical parts. For example, the width of the contact surface between the valve and the valve seat is specified as 1-2.2mm for the inlet valve and 1.5-2.5mm for the exhaust valve.
However, in actual maintenance, many people think that it is better to be a little wider than a little narrower, and they are used to choosing the upper limit or close to the upper limit, because the width of the valve working surface just repaired is close to the limit of use. Another example is the valve foot clearance, which is generally specified as 0.2-0.25mm for vehicles, but it is also considered that a larger clearance is better than a smaller clearance in maintenance and adjustment. Therefore, if it is used beyond the upper limit, in fact, the clearance is too large, which will not only reduce the engine power, but also cause knocking and early damage.
2. Smooth grinding of valve
In the maintenance of mixer truck, if the valve appears ablation, pitting and depression, it should be polished, usually on the grinder. Four problems should be paid attention to during operation: first, ensure that the valve head is concentric with the rod, otherwise it should be straightened first; Second, on the premise that the smooth grinding vehicle can grind a complete cone, the smaller the better; Third, try to improve the surface finish; Fourth, the depression at the end of the valve stem should be ground flat.
3. Hinge pin of valve guide
The fit clearance between the valve stem and the valve guide is the key to determine the service life of the valve guide. Therefore, when replacing the new valve guide, the fit clearance should be strictly controlled when hinge pin is used. The lower limit of the clearance specified by each mixer model can effectively prolong the service life.
4. Grinding of valve
The grinding of valves can be divided into two cases: first, there are only slight pits between valves and valve seats, and there is no need for light grinding and grinding when pinning; Second, the valve and valve seat are polished and ground after hinge pin. The former is first ground with full gold steel sand, then the pitting is removed, then ground with fine emery, and then coated with engine oil until the sealing meets the requirements and the width meets the regulations. The latter can only be grinded when the sealing performance fails to meet the requirements, but it must be noted during operation that excessive force is not allowed, and it is strictly forbidden to knock the valve up and down, otherwise concave sand marks will appear, affecting the maintenance quality.
It's not terrible that the mixer truck engine breaks down. The terrible thing is that the maintenance is not correct, and the performance of the engine will only get worse and worse. Therefore, the existing problems should be dealt with in time, and more content can be found on the website Consult.