Part number for hose connector

[xantia_v6]

It could be that the cooling system is being over-pressurised.
The simple cause for that is a filler cap which is faulty and not releasing excess pressure.
It could be a faulty thermostat, but then you would see high temperatures on the temperature guage.
It could be that there is localised boiling because the system has not been bled properly.
Another possible cause is head gasket failure which is causing too much gas in the cooling system that the pressure-release cap cannot handle.
or it could just be that the radiator is old.

[zeeshanzaki]

Thanks for the quick response.

There could be two reason then,
Filler Cap -I am suspecting the filler cap as it is very hard to open and close. Before this incident when I used to close,it always become loose after after final turn. But last time it tight so hard. Could that be issue as it is not allowing to release the pressure. What is the proper procedure to open and close this type of filler cap.

Or May be cooling system not bled properly when I replaced coolant last year. This might have caused air bubble in the system.

I will try replacing radiator and filler cap.

[zeeshanzaki]

Replaced the radiator and this time i bleed air through heater hose screw and a radiator. When I filled up it took almost same amount of coolant that I drain. So I hope there is no air int he system. Old radiator had hair line crack on the top.