Too much rust...... You better not pour in coolant.. Otherwise leak's may pop out. If you want to pour in coolant then change the metal pipes make sure your head gasket is ok. radiator is rust free.
Best method to check head gasket would be a compression test i think...
In my point of view a car without t.valve always gives smal bubbles in radiator some years ago our cultus 2007 carby was running without t.valve and that car usually show bubbles in radiator after placing the t.valve in the system the bubbles never appeard again.....
your car's water body(water pump) may also develop leak's if that is rusted too much...
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