Component Tests and General Diagnostics
PRESSURE CAP TESTINGCAUTION: Vehicles equipped with (2.0L/2.4L) engines use a different pressure cap than vehicles equipped with 2.7L engines. The pressure caps are NOT interchangeable. Verify proper pressure cap part number.
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 Cooling System Tester 7700. 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.
CAUTION: 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.
Fig. 20:
If the pressure cap tests properly while positioned on Cooling System Tester (Fig. 20), but will not hold pressure or vacuum when positioned on the filler neck. Inspect the filler neck and cap top gasket for irregularities that may prevent the cap from sealing properly.
COOLING SYSTEM PRESSURE RELIEF TESTING
WARNING: 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.
CAUTION: Vehicles equipped with (2.0L/2.4L) engines use a different pressure cap than vehicles equipped with 2.7L engines. The pressure caps are NOT interchangeable. Verify proper pressure cap part number.
Fig. 21:
The pressure cap upper gasket to filler neck seal can be checked by removing the overflow hose at the filler neck overflow nipple (Fig. 21). Attach the radiator pressure tester to the filler neck overflow nipple, and pump air into the system. The pressure cap upper gasket should relieve pressure at 69 - 124 kPa (10 - 18 psi), and hold pressure at 55 kPa (8 psi) minimum.
There is no need to remove the pressure cap at any time except for the following purposes:
^ Check and adjust coolant freeze point
^ Refill system with new coolant
^ Conducting service procedures
^ Checking for leaks
WARNING: If vehicle has been run recently, wait 15 minutes before removing cap. Place a shop towel over the cap, and without pushing down, rotate it counterclockwise to the first stop. Allow fluids to escape through the overflow tube. When the system stops pushing coolant and steam into the coolant recovery tank and pressure drops, push down on the cap and remove it completely. Squeezing the radiator inlet hose with a shop towel (to check pressure) before and after turning to the first stop is recommended.