Car overheating, coolant boiling. Advice appreciated

2003 Jeep Liberty, ran very hot last night and started smoking. When i popped the hood the coolant was visibly boiling (this could be heard from inside as well). Radiator is brand new (1 week old). What could this be?

These are symptoms of postcombustion gasses - and their heat and pressure - getting into the cooling system. A leaking head gasket is the most likely cause; a crack in the head or block less likely.

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If you overheated prior to replacing the radiator…the head gasket may have been damaged.

a new radiator won’t fix that.


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What came first? the chicken or the egg?

It’s likely that the head gasket failed and destroyed the original radiator.

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The radiator wasn’t replaced because of overheating, it had a small crack. The overheating happened for the first time last night

And so the age old question goes unanswered.

But if you see vigorous bubbling at the coolant reservoir it is likely that the bubbles are exhaust gas that has escaped the combustion chamber and the most likely escape route is the head gasket and in your situation it doesn’t matter which came first. It is very likely that you will need to have both heads removed and checked for warping and repaired or replaced and then installed with new gaskets. That’s from the “most likely” answer to your question. Have an independent mechanic with a good reputation who has experience with late model Jeeps to diagnose your problem and post his recommendation and estimate here. I feel sure someone(several) here will nit pick everything the mechanic says. You’ll get some insight and regulars here will have some fun.


Check if the radiator fan is working. Also if the cooling system cap isn’t holding pressure the coolant will boil at normal operating temperatures.

Verifying the fan is working and pressure testing the cooling system and radiator cap is a good idea. Beyond that, remove the thermostat and put it in a pan of hot water on the stove to see if it is working or not. If it is stuck closed or won’t fully open, this could be the symptom. A faulty water pump is less likely, but should be considered. Suggest to not drive the vehicle until this is resolved, otherwise you may damage your new radiator, or worse.