The lower radiator pipe may be cold due to various reasons, particularly the following:

1. radiator soiling;
2. thermostat jamming;
3. ingress of air into the system;
4. malfunction of the water pump.

In order to define a defect cause, apply for help to specialists. Remember: the radiator lower pipe not always should be hot. At low environmental temperature, when the engine is not warmed up and cooling liquid circulates through the small circle, it will stay cold. It is normal.

Usually, air ingresses into the cooling system by many reasons. One of them – failure of the expansion tank cap. If its thread is worn, air intake occurs. It accumulates in the expansion tank or other elements of the cooling system, and at the engine rpm increase, this air may force out the coolant.If the cap valve, designed for excessive pressure blow, is jammed, hoses, pipes and the radiator will break down due to time. This will lead to appearance of airlocks. According to their location, cooling system or accessory units and assemblies, such as heating radiator, may work improperly.

Also poor-quality priming of the cooling system after antifreeze refill may also cause an appearance of airlocks. Sometimes exhaust gases ingress into the cooling system. Usually it is caused by crack in the cylinder head or its gasket wear-out.

According to designation, automotive radiators can perform various functions. The engine radiator maintains the temperature optimal for its operation and it is very important element of the cooling system. It is mounted in the front part of vehicle and is protected from mechanical damages with the special grill.

Liquid inside of the radiator moves through pipes of different cross-section, plates or corrugated band, speeding up its cooling, are molded to it. Fans, blowing to the radiator with cold air, and diffusers which regulate air flow direction are used for higher efficiency of heat-exchange processes. Excessive pressure release is performed by the radiator cap, equipped with inlet and drain valves.

Heating radiators serve for cabin heating. They are constructed in the same way, but in their construction there are swirlers in order to improve heat-exchange. The oil radiator, usually is used as auxiliary, serve for oil cooling in the lubrication system of the engine, transmission, liquid in the steering control, and also sometimes for oil in the reductor.