Coolant Bottle Pressure Cap
WARNING:
The warning words "DO NOT OPEN HOT" on coolant bottle pressure cap is a safety precaution. When hot, pressure builds up in cooling system. To prevent scalding or injury, coolant bottle pressure cap should not be removed while system is hot and/or under pressure.
CAUTION:
If vehicle has been run recently, wait 15 minutes before removing cap. Then place a shop towel over cap and without pushing down rotate it counterclockwise to first stop. Allow fluids to escape through overflow tube and when system stops pushing out coolant and steam and pressure drops, remove cap completely. Squeezing radiator inlet hose with a shop towel (to check pressure) before and after turning to first stop is recommended.
The pressure cap upper gasket (seal) pressure relief can be checked by removing cap. Attach Radiator Pressure Tool to cap and pump air into cap. Pressure cap upper gasket should relieve at 18 psi (124 kPa) and hold pressure at 16 psi (110 kPa) minimum.
Remove pressure tester and hold cap in hand, right side up. See Figure . The vent valve at bottom of cap should not open. If rubber gasket has swollen and prevents valve from closing, replace cap.
Hold cleaned cap in hand upside down. If any light can be seen between vent valve and rubber gasket, replace cap.
There is no need to remove pressure cap at any time except for the following purposes:
- Checking and adjusting antifreeze freeze point.
- Refilling system with new coolant.
- Conducting service procedures.
- Checking for vacuum leaks.