Radiator Cap

RADIATOR PRESSURE CAP Special Tools: Dip the pressure cap (1) 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 Pressure Tester. 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. If the pressure cap tests properly while positioned on Pressure Tester (2), 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.

OPERATION The pressure cap allows the cooling system to operate at higher than atmospheric pressure which raises the coolant boiling point, thus allowing increased radiator cooling capacity. The pressure cap releases pressure at some point within a range of 110 kPa ± 14 kPa (16 psi ± 2 psi). A spring-loaded vent valve in the center of the cap allows the system to pressurize and depressurize without creating a vacuum. If the valve is stuck open, coolant will escape to the overflow hose. There is also a gasket in the cap to seal to the top of the filler neck.

RADIATOR PRESSURE CAP The cooling system's pressure cap is located on the radiator for 3.7L. The cap construction includes; stainless steel swivel top, rubber seals and retainer, main spring (1), and a spring loaded valve (5).

1 - MAIN SPRING 2 - GASKET RETAINER 3 - STAINLESS STEEL SWIVEL TOP 4 - RUBBER SEALS 5 - SPRING LOADED VALVE 6 - COOLANT PRESSURE BOTTLE 7 - FILLER NECK 8 - OVERFLOW NIPPLE

The cooling system cap is located on the coolant pressure bottle for 3.7L/2.8L The cap construction includes; stainless steel swivel top, rubber seals and retainer, main spring (1), and a spring loaded valve (5).

The pressure cap allows the cooling system to operate at higher than atmospheric pressure which raises the coolant boiling point, thus allowing increased radiator cooling capacity. The pressure cap releases pressure at some point within a range of 110 kPa ± 14 kPa (16 psi ± 2 psi).

A spring-loaded vent valve in the center of the cap allows the system to pressurize and depressurize without creating a vacuum. If the valve is stuck open, coolant will escape to the overflow hose. There is also a gasket in the cap to seal to the top of the filler neck.

CAUTION: Use only the pressure cap specified for this vehicle. Use of other pressure caps can lead to coolant loss and overheating.

1 - OVERFLOW NIPPLE 2 - MAIN SPRING 3 - GASKET RETAINER 4 - STAINLESS-STEEL SWIVEL TOP 5 - RUBBER SEALS 6 - VENT VALVE 7 - PRESSURE BOTTLE 8 - FILLER NECK

The pressure cap upper gasket (seal) pressure relief can be checked by removing the overflow hose at the radiator filler neck nipple. Attach the Pressure Tester 7700 to the filler neck nipple (1) and pump air into the radiator. Pressure cap upper gasket should relieve at 69-124 kPa (10-18 psi) and hold pressure at 55 kPa (8 psi) minimum.

WARNING: The warning words "do not open hot" on the radiator pressure cap is a safety precaution. When hot, pressure builds up in cooling system. To prevent scalding or injury, the radiator cap should not be removed while the system is hot or under pressure.

There is no need to remove the radiator cap at any time except for the following purposes:

  1.   Check and adjust coolant freeze point.
  2.   Refill system with new coolant.
  3.   Conducting service procedures.
  4.   Checking for vacuum leaks.

WARNING: If vehicle has been run recently, wait 15 minutes before removing cap. Then place a shop towel over the cap and without pushing down rotate counterclockwise to the first stop. Allow fluids to escape through the overflow tube and when the system stops pushing coolant and steam into the crs tank and pressure drops push down and remove the cap completely. Squeezing the radiator inlet hose with a shop towel (to check pressure) before and after turning to the first stop is recommended.

1 - PRESSURE CAP 2 - PRESSURE TESTER

Dip the pressure cap (1) in water. Clean any deposits off the vent valve or its seat and apply cap to end of the Pressure Cap Test Adapter that is included with the Pressure 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.

If the pressure cap tests properly while positioned on Pressure Tester (2), 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.

Clean the radiator pressure cap using a mild soap and water only.

Visually inspect the pressure valve gasket on the cap. Replace cap if the gasket is swollen, torn or worn. Inspect the area around radiator filler neck for white deposits that indicate a leaking cap.