My lower radiator hose suddenly burst out last night (MAZDA 626, 1993, AUTO). After replacement with new hose it seems that the cooling system is not normal anymore. This morning while filling the radiator with water with engine running, I noticed that the water is slowly boiling. I immediately shut off engine and the water burst out. I want to ask what is the possible problem / solution to solve this. Many thanks.

 

Hard to say for sure...

Perhaps your water pump isn't pumping the water through... or not fast enough.

Maybe your thermostat isn't working properly.

Is your fan working? If the airflow through the radiator isn't sufficient then it's not going to cool the fluid even if everything else is perfect.

You might want to turn your heater on full and blast "hot" air into the passenger compartment. If that helps then either your radiator isn't cooling fast enough or your engine is getting too hot.

It's also possible that something else is wrong and this is just a symptom. On some early mustangs you can reduce the temperature by playing with the timing...

Again, sorry that this is fairly generic advice.... I'd start by checking the thermostat, and then maybe replace the water pump.

Z.