Big radiator tube shrinks when switching modes on heater from vent to defrost
Refreshing coolant after heater core replacement. Add 1,5 gallon of distilled water in
radiator to flash to remove residues of old coolant. Put heater on max in mode "vent".
Start engine. Then after 10-15 minutes of engine idling, I've turned heater mode from
"vent" to "defrost' and upper radiator tube shrinks extremely and engine sound is
changing. Coolant temperature is always in normal. And bubbles always coming out in
coolant reservoir. By the way one of heater core tubes that goes "in" is hard and hot,
but other tube that goes "out" is quite soft. Any versions? Thank You!