Could be an airlock. try bleeding the system until the heaters are hot. If it keeps doing it the i would suspect cyl head gasket. Hope this helps
Bad head gasket? Bad thermostat? Defective radiator cap?
The overflow bottle may overflow if: 1. The car is overheating - this means after the coolant in the radiator gets heated up and expands it flows to the reserve bottle but the radiator doesn't cool down to suck back the coolant from the overflow bottle, but just keeps on sending coolant to the bottle. 2. You may have put excess coolant in the bottle - hence heated coolant from the radiator didn't get enough space.
If your 1997 Subaru Legacy is the same as My RS-B Twin Turbo?, the Radiator and Overflow bottle have to come out and the Thermostat is at the front of the Engine, down the bottom-just to the right of centre, (Thermostat is inside the bottom radiator hose), - My Thermostat just twisted/pulled out, let all old coolant flush out-put New Thermostat in its place, Radiator and Overflow bottle were put back in and radiator topped up with fresh coolant and water, Overflow was filled to second line as it should be, car was started with heater on full for 5 minutes to disperse any air in water - (note) after adding fresh coolant, add water in Radiator till it can't take anymore-to show its filled properly.
no antifreese
yes
Coolant is added to the overflow bottle instead of the radiator. The overflow bottle will allow fluid to fill over into the radiator.
An overflow tank is a bottle that holds coolant that expands and leaves the radiator under driving conditions. The Coolant will go back into the radiator as needed.
You add coolant to a C240 at the radiator overflow tank. This allows the radiator to suck in coolant as needed when hot.
Through the overflow tank. Open the bleeder valve on the thermostat housing, turn heat to high, and pour coolant in the overflow tank until it comes out the bleeder valve.
Blown head gasket?
You could have a bad water pump causing no coolant flow, inoperable radiator fans, a coolant leak,............
The thermostat.