Radiator Pressure Tester
A hand pump tool equipped with pressure adapters used to pressurize the cooling system to diagnose leaks.
A radiator pressure tester is a diagnostic hand pump fitted with a pressure gauge and a series of threaded or bayonet adapters. The tool is attached to the radiator filler neck or the coolant expansion tank in place of the pressure cap. By pumping the handle, the mechanic manually introduces air pressure into the cooling system, simulating the pressure built up when the engine is hot.
Pressurizing the system when the engine is cold is a highly effective way to locate leaks. It allows the mechanic to safely inspect hoses, water pumps, radiators, and heater cores for dripping coolant without risking burns from hot coolant or moving engine parts. The system is typically pressurized to the rating stamped on the radiator cap (usually 12 to 16 psi) and monitored; if the gauge needle drops, a leak is present.
The pressure tester can also be fitted with an adapter to test the radiator cap itself. A cap that fails to hold its rated pressure will allow coolant to boil at a lower temperature and overflow into the reservoir, causing overheating. This tool is essential for diagnosing internal leaks like blown head gaskets, where coolant is forced into the cylinders.