Cooling System Pressure Cap Testing
| 1 - PRESSURE CAP |
| 2 - PRESSURE TESTER |
The warning words "DO NOT OPEN HOT" on the pressure cap is a safety precaution. When hot, the cooling system builds up pressure. To prevent scalding or other injury, the pressure cap should not be removed while the system is hot and/or under pressure.
Dip the pressure cap in water. Clean any deposits off the vent valve or its seat and apply cap to end of the Pressure Cap Test Adaptor that is included with the (special tool #7700, Tester, Cooling System). Working the plunger, bring the pressure to 104 kPa (15 psi) on the gauge. If the pressure cap fails to hold pressure of at least 97 kPa (14 psi), replace the pressure cap. Continue adding pressure to cap. The pressure cap should relieve at 144 kPa (21 psi) and hold pressure at 110 kPa (16 psi) minimum.
The Cooling System Tester Tool is very sensitive to small air leaks that will not cause cooling system problems. A pressure cap that does not have a history of coolant loss should not be replaced just because it leaks slowly when tested with this tool. Add water to the tool. Turn tool upside down and recheck pressure cap to confirm that cap is bad.
If the pressure cap tests properly while positioned on Cooling System Tester, but will not hold pressure or vacuum when positioned on the radiator. Inspect the coolant bottle filler neck and cap top gasket for irregularities that may prevent the cap from sealing properly.
There is no need to remove the pressure cap at any time except for the following purposes:
- Checking and adjust antifreeze freeze point.
- Refilling system with new coolant.
- Conducting service procedures.
- Checking for vacuum leaks.