A new Ford Mondeo 2.0AT car (model code CD391) runs high in engine coolant temperature. Fault diagnosis: the car is an accident car. During the maintenance process, the front safety rod, the inlet grille, the radiator and the condenser and other components are replaced. After the maintenance is completed, the road test is carried out. After a high speed for a period of time, the instrument shows that the temperature of the engine coolant is too high. IDS detection, no fault code storage; open the engine chamber cover inspection, found that the cooling liquid level in the expansion tank is normal, and the cooling fan is normal operation; hand touch the radiator and lower cooling liquid pipeline, are more hot, indicating that the temperature device is basically normal. Exhaust the air in the cooling system thoroughly, and the failure is still the same. Is there a slight "punching" phenomenon in cylinder block failure? Remove the cylinder spark plug, no sign of "whitening". Taking into account the smooth running of the engine and the expansion chamber without bubbles, exclude the possibility of cylinder pad damage. When the ignition switch is disconnected and then connected, it is found that the self checking action of the upper and lower intake grille is not synchronous. The intake grille is composed of two parts: the upper and the lower parts, and a connecting rod in the middle. The opening and closing of the intake grille are driven by the motor at the lower part of the intake grille. After removing the intake grille, it is found that the connecting rod of the upper and lower intake grille is not installed. Then why did the replacement grille not install the connecting rod? Communicating with the former maintenance personnel, when the maintenance personnel removed the intake grille from the warehouse, there was no connecting rod, so they thought there was no need to install it. When asked about the fittings, it was learned that the connecting rod of the intake grille is supplied separately, and is not provided with the intake grille. Troubleshooting: the correct installation of the ordered inlet grille connecting rod (the inlet grille connecting rod is installed in the rear of the front anti-collision steel beam, the reliability of the connection should be paid special attention to the installation), and the failure is ruled out.