CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Cooling system problem?

I have a 96 Nissan Altima with 160k miles. Today after driving it for two hours, I noticed that the temperature gauge was fluctuating and going down. I pulled over and found that: 1) the coolant hoses are not as hot as it should be; 2) there was no pressure when I tried to open the radiator cap.



Good thing is that the coolant looked full and very clean.



What might have been the problem?



Thank you!

Perhaps the thermostat is bad, and the engine is not reaching correct operating temperature. A thermostat stuck open will do this.

You’re lucky you didn’t scald yourself. You should never remove the radiator cap when the engine is warm. The fact that you got away with it is more evidence the coolant is not getting as hot as it should.

Running the engine at below-normal temperature will reduce your fuel mileage. I suggest you replace the thermostat and the radiator cap and see what happens.

How does your heater work?

Thank you very much for your fast reply. So if the thermostat is stuck open, the car won’t get to normal temperature even after two hours of driving? The car was runing at normal temperature before this happened. I think once the car is hot, a stuck open thermostat and a normal working thermostat should work the same (both of them will be open), am I right?

The heater was not very hot but ok.

You’re assuming the thermostat, once open, stays open; and, you’re assuming that the is, either, fully open, or, fully closed. No, and, no.

think once the car is hot, a stuck open thermostat and a normal working thermostat should work the same (both of them will be open), am I right?

No! It should cycle to keep the engine at design (optimum) temperature.

I see. Thank you very much for the replies.