Generally, the normal engine water temperature should be about 90 ℃. Once it is too high or too low, it will rise or fall rapidly. There's something wrong with the car's cooling system.
 If the water temperature alarm light is on, it may be caused by the following reasons. You can refer to it when troubleshooting.
 1 Insufficient coolant
 Coolant leakage will cause its temperature to rise. At this time, check whether the coolant leaks! If so, repair the leaking pipes as soon as possible. If not, add coolant of the same brand in time! It is not recommended to add water, especially in winter. Even if there is no fault, it will dilute the coolant!
 2. There is a problem with the cooling fan
 Heat dispersal
 Fan
 It will cause that the heat generated during the high-speed operation of the vehicle cannot be transferred to the antifreeze in time, which will affect the
 dissipate heat
 Then, the temperature of antifreeze will rise, causing problems such as boiling! If this happens, reduce the speed first during driving. Check whether it is a fan problem. If it is, repair it in time. Don't wait for the boiler to open!
 3 Circulating water pump problem
 Water pump
 Once the condition occurs, the water circulation on the heat conduction side of the engine cannot be carried out normally. As a result, the engine cooling system fails, and the "boiling" phenomenon will occur! We must find out and solve the problem in advance. Generally, the water pump has a problem, which may be the bearing is locked or the louver is damaged!
 Bearing
 It is unlikely to lock. If the shutter is broken, just replace it!
 If the water temperature indicator is on, how to deal with it:
 1. The best water temperature when driving is about 90 degrees.
 If it is overheated, it may boil, which is commonly known as "boiling". After the water temperature alarm light on the instrument panel lights up, it is not suitable to continue driving. You can stop to check the car cooling system. If the problem is not serious, you can drive to the maintenance station for inspection and maintenance after the water temperature drops.
 2. When the water temperature alarm light is on and the water temperature alarm is too high, slow down and stop first
 Then drive the car to the side of the road. Don't rush to turn off the engine because
 Water temperature is too high
 The temperature of piston, steel wall, cylinder, crankshaft, etc. will be too high, the oil will become thin, and the lubrication function will be lost. If the engine is shut down at this time, the parts are in expansion state, and the clearance between the parts is very small. Some soft metals fall off after shutdown, and some even cause cylinder sticking. Therefore, do not turn off the ignition immediately after the boiler is opened, but temporarily keep idling and try to cool down.
 3. When cooling down, do not pour cold water on the engine. This may cause the engine block to burst due to sudden cooling.
 The correct way is to wear gloves, add a piece of folded wet cloth on the water tank cover, gently unscrew the water tank cover by a small seam, and replenish cold water or antifreeze after the water vapor slowly discharges and the water tank pressure drops.
 Mercedes Benz glk300 reports that the coolant temperature is too high
 The reasons are: 1. Insufficient coolant: the long time water circulation of the engine will cause the loss of coolant from the engine cooling system, resulting in water shortage in the water tank 2. Water tank leakage: the water tank connecting pipe is broken or loosely connected, which will cause water leakage and hinder the water circulation
 3. Cooling fan failure: the cooling fan is damaged or short circuited, causing the fan to work or the cooling fan to rotate slowly. The water temperature of the car reflects the working condition of the car cooling system, and the engine must run at a suitable high temperature. When the engine coolant temperature is about 90 degrees, the engine will reach a good operating state. At this temperature, the temperature of the combustion chamber is enough to make the fuel completely evaporate, so the fuel can be burned better and the gas emissions can be reduced.