96 Sentra... Overheating mystery... need suggestions!

I have a 96 Nissan Sentra with a 1.6 liter engine and has 120k miles. It recently began overheating and I had to turn on the interior heater to drop the temperature down. Since I do most of my own work on the car, I have done done a number of things to resolve the problem... but, with no luck so far. I need some suggestions on what else I can do.

Here is what I have done so far:

  1. Brought the radiator to the radiator repair guy in town. He did an informal flow test (put a hose in one opening and watched the outflow out of the other). He said that in his opinion the radiator had sufficient flow.... surely enough flow so that it shouldn't have caused the problem I experienced.

  1. Changed out the water pump and thermostat. I decided with 120 k miles on the car, I wanted to do this anyway.

  2. I checked the fluid in the radiator as the engine was warming up and thought I saw bubbling. Additionally, I saw signs of vapor coming out of the tail pipe as I was starting up. Lastly, it seemed that my antifreeze levels had been coming down in recent weeks without signs of obvious leakage. All this convinced me that I must have a blown head gasket.

I brought the head to a automotive machinist in town and his estimation was that the head did not show signs of antifreeze leakage in the head combustion area. He indicated that the valve area of the leakage would show obvious signs if such leakage occurred.

After all of this I am not sure what I should check out next. I need suggestions. My first thought is that maybe I should change out the radiator anyway just to eliminate that as a problem. What do you think??

Al Kondo

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Al Kondo
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On 1/7/2005 12:48 PM US(ET), Al Kondo took fingers to keys, and typed the following:

Radiator fan(s) working properly? Are the radiator hoses in good shape, and not overly soft? When the engine gets hot, does either of the hoses look compressed? If so, replace them. Did you have the engine power flushed either before the radiator removal, or after the reinstallation?

The bubbling you saw was probably due to air getting into the system after you removed the radiator, which opened the system to the atmosphere. The trapped air will gradually get circulated to the radiator's top tank after running the engine for a while. Just keep topping off the radiator or overfill tank as the coolant level goes down. Water vapor coming from an exhaust pipe when first starting is not unusual. A large amount of water vapor coming from an exhaust pipe in cold weather, is not unusual for a longer period of time after starting. Some water vapor is produced in the combustion process and exits the pipe as steam. It's just more visible when it is cold out. You can throw money at the system trying to find out what the problem is, and failing that, take it to a radiator shop and have it professionally diagnosed for more money, or you can take it to the shop first and let them throw your money at the right solution.

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willshak

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