Cooling System Pressure Test Cost Estimate

To perform a cooling system pressure test, a technician will first make sure that the engine temperature has dropped so it is not hot to the touch. Opening a hot cooling system can cause serious injury. Then the radiator cap, or the cap to the expansion tank (overflow bottle), is removed and engine coolant is added until the system is full. Next, the technician will install a pressure tester (usually an air pump with a pressure gauge attached) in place of the cap, and pump air into the cooling system. The air compresses and shows a positive pressure reading on the gauge. The technician will observe whether the system can hold the pressure or not. If the pressure drops, a leak is present somewhere in the system.

A coolant leak can develop in any of several locations within the engine cooling system. A leak on the outside of the engine may spring from a weak spot or tear in a radiator hose, at the hose connections, from a hole in the radiator, from a bad seal at the water pump, in the heater core underneath the dashboard, and so on. Inside the engine, a bad intake manifold gasket or cylinder head gasket can cause coolant to leak; so can a crack in the cylinder head or the engine block.

RepairPal recommends that the cooling system be thoroughly inspected by a qualified technician at a trusted repair facility as soon as possible when signs of overheating appear.

An engine in a late model vehicle is designed to run somewhere between 195 and 220 degrees. But the fluid in the cooling system can rise well in excess of 220 degrees when the engine overheats. This produces steam that will cause severe injury from scalding if the system is opened when hot and under pressure. Burns are possible as the engine components are also at a high temperature. Extreme caution should be exercised when working on a hot engine, especially one that is overheated. If steam is seen coming from under the hood, the engine should be allowed to cool for at least a half hour before the hood is opened, and the radiator cap should not be removed until the engine is cool enough to touch with a bare hand.

Someone with intermediate DIY experience and the proper equipment can perform a basic engine coolant system test. But this procedure only shows whether or not there is a leak in the system. It does not reveal the location of the leak.