I just replaced thermostat and water pump on 98 5.2 grand cherokee. Filled the radiator up and car boiled over. My question is the coolant in the radiator did not go down. How is that possible?
There is air trapped in the upper part of the engine.. Once the engine cools off ... take the radiator cap off and slowly squeeze the upper hose... you should see the level go down in the radiator. Refill and do it again until it stabilizes (some engines have an air bleed screw). Be sure to inspect the sealing ring on the cap for a tight fit before replacing
FYI ... A radiator must hold a minimum of 5 lbs pressure when the engine is hot or it will probably boil out. Low pressure is essential in a radiator to keep it from boiling