How to Pressure Test an Engine Coolant System

Automotive coolant, also called antifreeze, cools the engine when it gets too hot and keeps the engine from freezing at sub-zero temperatures. The temperature of an engine is controlled by the thermostat, because the thermostat opens and restricts the flow of the coolant in the engine. Engine cooling system parts can become weak or rotted over time. The weakening parts can in turn cause a drop in pressure if they start to leak. it should take about a half hour to testing the cooling system pressure.

Instructions

1

Open the hood, engine cover, or trunk deck lid on the vehicle. Locate and remove the radiator cap from the radiator, or pressurized radiator overflow bottle.

2

Install a fitting from the coolant pressure testing kit onto the hole from which you removed the radiator cap. There are several fittings in the kit. Try the fittings until you find one that best fits the radiator hole or pressure hole. When you find the correct fitting, place it onto the hose end of the pressure tester. Twist the fitting onto the tester hose until it locks.

3

Install the pressure tester hose and fitting onto the radiator hole, as you would the radiator cap.

4

Pump the pressure tester hand pump until the dial indicator is set at 16 pounds per square inch (psi). Read the dial indicator for no less than 10 seconds. Sixteen pounds is the regulatory pressure at which most vehicle engine cooling systems perform. Pumping the pressure to 16 psi lets you know if your cooling system is leaking at a normal pressure. If the dial indicator holds its pressure at 16 psi, then your cooling system is good a standard operating pressure.

5

Pump the pressure tester up to 25 psi. Watch the dial indicator for no less than 10 seconds. The test at 25 psi will tell you if the cooling system might lose pressure as a higher pressure level. If a thermostat is bad or stuck shut, the cooling system can apply a larger amount of pressure. If you hear any hissing or see any fluid leaking, stop this test immediately. If you notice no leaks, and the pressure tester dial stays at 25 psi, then your cooling system parts are good.