With malfunction in the cooling system at first check the level of cooling liquid in a broad tank, a tension of an auxiliary driving belt of the pump of cooling liquid and operability of the index of temperature.

If after start the engine gets warm very slowly, then perhaps the thermostat is in constantly open situation. It can be defined, having checked the branch pipe going from the thermostat to a radiator. If it grows warm right after start of the engine - the thermostat means it is open. In this case it needs to be replaced.

If the engine overheats, then a hand check temperature of the top hose of a radiator. If the index of temperature issues indications at which the thermostat has to open, and a hose cold, then, perhaps, the thermostat is in a closed position and does not pass cooling liquid to a radiator. In this case the thermostat is also subject to replacement.