Changed the coolant reservoir cap in the meantime. Used a black one instead of blue, for looks.
Just after the change, the coolant level is much more level (
), that is, it goes down just above the minimum line when cold and juts upwards to the maximum line when hot.
Before it went down much under minimum after running and cooling itself, and gushed out furiously air, coolant and brown gunk from the radiator sealer when opened hot.
The valve in the old cap must have been stuck closed due to dried coolant crusts, and it did not release properly the air when pressure built up. Which means the pressure oscillations in the cooling circuit due to this crappy plastic valve were the most likely culprits for the cracking of the heater core.
So the people who wish to avoid cracks in the cooling circuit and possible coolant losses should change their reservoir caps each 6-7 years or 70,000 - 80,000 kms.
Just after the change, the coolant level is much more level (
), that is, it goes down just above the minimum line when cold and juts upwards to the maximum line when hot. Before it went down much under minimum after running and cooling itself, and gushed out furiously air, coolant and brown gunk from the radiator sealer when opened hot.
The valve in the old cap must have been stuck closed due to dried coolant crusts, and it did not release properly the air when pressure built up. Which means the pressure oscillations in the cooling circuit due to this crappy plastic valve were the most likely culprits for the cracking of the heater core.
So the people who wish to avoid cracks in the cooling circuit and possible coolant losses should change their reservoir caps each 6-7 years or 70,000 - 80,000 kms.
