Radiator overheat but temperature gauge is still normal

How long has it been since the last time the cooling system was opened up? It could still be bleeding off air. Another issue could be an air leak into the system that prevents it from reaching the proper pressure and thusly has a lower boiling point. Another possibility is head gasket problems, but there should be other symptoms (white smoke, oil in the coolant, coolant in the oil, etc to go along with exhaust gas getting making bubbles) to go along with it.

Is the radiator is full up after complete cooling, check at the radiator itself, after a 20+ min drive and allowing the auto to cool for a few hours. If it is full up to the bottom of the radiator cap and the expansion tank is above the minimum lever it is operation correctly. I would suggest you keep an eye on both for a few days, if no change in levels then everything is good.

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Leaking coolant out the side, or just leaking somewhere unknown.

THIS is a sign that the radiator isn't getting up to pressure. Something somewhere is leaking. Check the cap.

If you hear it bubbling inside, that's a sign that either the temperature is too high, or the pressure is too low. You know the temperature is okay, from the gauge. So it has to be the internal pressure.

--scott

Thanks for all the replies. After searching in this group, I found it is not an uncommon problem. A lot of people had the same problem before.

After driving for few days, the air in the cooling system should have been bleeding out already. But, the bubbling still happens.

I have replaced the radiator cap, but the condition did not change. I also found that the bubbles come out around 1 to 2 minutes after a cold start. The temperature gauge has not moved up, so I think the coolant should not be hot enough to generate bubbles so soon. The bubbles comes out slowly like 2 to 3 seconds per bubble.

So, I am leaning toward the head gasket problem. But, I do not see white smoke when starting the car. The coolant has no mix of oil, and the oil seems OK. For the head gasket problem, can it be possible that only air from engine can go into the cooling system but coolant cannot go into the engine?

Thanks

Hs> hs> >I have a 95 Toyota Camry (4 cycl. auto transmission). The temperature

The bubbles on start up may be normal depending on how the system is designed. Also some trapped air can be rather stubborn to get out.

If there are no other classic head gasket symptoms then probably not. The coolant is pressurized by the water pump, if the gasket for a passage is breached it will push coolant through that breach. You would be loosing coolant and it would have to go into the oil or out the exhaust.

Bubbles can also be a sign of a failing water pump shaft seal.

nate

For the head gasket problem, can it be possible that

Absolutely ! The pressure in the cylinders is in the hundreds of pounds, the pressure in the cooling system is less than twenty. It's possible to have a head gasket leak under the pressure of combustion but not let coolant into the cylinders because of the low cooloing system pressure.