Cooling System Pressure Relief Testing

DIAGNOSIS AND TESTING - 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.





The pressure cap upper gasket to filler neck seal can be checked by removing the overflow hose at the filler neck overflow nipple. 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 CRS 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.

CLEANING
Use only a mild soap to clean the pressure cap.

INSPECTION

CROSS-SECTIONAL VIEW





TOP VIEW

Hold the cap in your hand, right side up.
The vent valve at the bottom of the cap should open with a slight pull. If the rubber gasket has swollen, preventing the valve from opening, replace the cap.
If any light can be seen between vent valve and the rubber gasket, replace the cap. Use only a replacement cap that has a spring to hold the vent shut.
A replacement cap must be of the type designed for coolant reserve systems. This design ensures system pressurization.