What’s wrong with the water temperature in the van not coming up?

Thermostat failure.

The engine temperature does not come up or heats up very slowly, and the warm air is not hot. Most of the time, the water temperature rises when there is a traffic jam or waiting for a red light, and the temperature drops rapidly when the car is running.

The main reason for this situation is a thermostat failure, which always remains in a large cycle state. This will be improved immediately after replacing the thermostat.

Solution:

You can change the thermostat, observe whether the thermostat is completely closed at room temperature, and then put the thermostat in hot water to see if it can be opened. The higher the water temperature, the greater the degree of opening, and there is basically no problem with the thermostat. Or cover part of the water tank and cover two-thirds of the front of the water tank with cardboard. Or the size of the cardboard can be adjusted flexibly depending on the water temperature. Very effective and affordable.

Extended information:

When designing the engine cooling system, engineers will give priority to engine heat dissipation, and then ensure the normal operation of the heater. When the coolant is insufficient, the coolant will be given priority to circulate in the engine. At this time, there is no "water" in the heater circulation pipe, and most of the heater water tank is air. At this time, the air conditioner heater is naturally not hot.

The position of the heater water tank can be seen from inside the engine compartment. In some models, the position of the heater water tank will be higher than the cylinder block, at the same level as or higher than the cylinder head. This ensures that when the coolant is insufficient In this case, priority is given to circulating the coolant in the cylinder block and cylinder head. After replenishing the coolant, the heater water tank will be filled with hot coolant, and the heater will naturally heat up.

The structure of the heater water tank is actually a reduced version of the engine water tank radiator. There are many small heat dissipation pipes inside, which are easily clogged like the water tank radiator. When the inside of the heater water tank is clogged, the coolant flowing through becomes slower, the flow becomes smaller, the heat is insufficient, and the air conditioner warm air is naturally not hot.