TRIDON Radiator Cap W/ Liver For Mitsubishi Starwagon SF - Carb. 2.4L 4G64 4 Cyl. Tridon is a major Australian owned auto parts manufacturer. Mitsubishi Starwagon SF - Carb. 2.4L 4Cyl. 4G64 8V SOHC, 10/86-08/90.
Besides the obvious safety factor that this cap offers, it is perfect for a cooling system that is being over pressurized from a leaky head gasket / crack.
If the excess pressure that leak produces, is not vented at the end of the drive, the coolant recovery system cannot work.
Careful (very careful) venting using the lever (and NOT cap removal) does this, and once everything has then cooled down naturally, the system works as it should; drawing the overflow coolant back into the radiator.
And, Yes. Use extreme Caution, always. Hot scalding water takes no prisoners. Don't remove the cap until the system is truly COLD.