Honda CR-V, which runs about 10 thousand km. The temperature of the car's daily coolant is normal. When driving at 120km/h speed on high speed, the coolant temperature is normal. When the temperature of the coolant is running at the speed of 130km/h, the temperature of the coolant begins to rise slowly. The owner is worried about the problem of the vehicle, and then goes down to the store to check it. This fault feels strange, test car found really so, in general case, if the driving engine is open, then when the original acceleration can also open the pot, in the original idle, medium speed, high speed test, cooling liquid temperature has been normal. At this point, someone asked whether there was any malfunction in the vehicle. If driving at 130krn/h speed, will the coolant temperature increase, or will it not increase at a certain temperature? To verify whether the car was in trouble, a test drive was found and a test was on the road. As a result of the speed of 130km/h, no matter how long it was, the temperature of the coolant remained constant. The examination result shows that the cooling system of the vehicle is defective. Remove the pump and check it. After inspection, the thermostat is normal, the fan works well, the water pipe is not abnormal, the radiator cap is normal, the radiator is removed and the cleaning is not clogged, and the failure phenomenon still exists. At the same time, it is doubtful whether the coolant fan does not turn in the running process, so the fan is short connected to make it work all the time. On the road trial run, the fault still exists. The maintenance work is in a stalemate for a while. Is it a cylinder pad? There are 2 reasons for this phenomenon. First, the engine runs smoothly; second, there is no sign of water intake from the spark plug. However, the parts that have been inspected have no problem, and the cylinder head inspection is decided immediately. When the valve and cylinder head are removed, when the cylinder head bolts are removed, it is found that the 2 cylinder head bolts of the 2 cylinder and the 3 cylinder have insufficient torque. Remove cylinder head and check cylinder gasket, cylinder head and cylinder. It is possible to analyze the loosening of the cylinder pad bolts. When the engine is loaded, the combustion gas in the cylinder enters the cooling system in the intake stroke, causing the high temperature of the coolant. To analyze this step, we replace the cylinder gasket, tighten the cylinder head bolts according to the prescribed torque, and check after the trial run, troubleshooting. Summary: the maintenance of the problem of excessive water temperature of the vehicle should be checked from simple to difficult, and a reasonable way of inquiry can be adopted to find the cause of the failure faster.