96 Sentra... Need advice on overheating problem

I have a 96 Sentra with a 1.6 liter engine with 120k miles.
Recently, I have had an overheating problem. It occurred on a trip
to Florida (from Texas). I handled it on the trip by turning on the
interior heater. Fortunately, it was pretty cool outside and the
heat on the inside was beneficial.

Thinking the problem was the radiator, I brought it to a shop
yesterday. The tech there did some flow tests and indicated that he
didn't think that the radiator would have caused the problem I
experienced. I also checked the thermostat by placing it in some
boiling water to see if it functioned correctly..... it did. After
reinstalling the radiator and the thermostat, I ran the car today in
the garage to see if the overheating continued. Here is what I
found:

1. the fluid was boiling in my overflow container, while the temp
gauge read in the middle range.

2. the lower hose from the engine to the radiator was cool to the
touch after running the engine 10 minutes in the garage. The upper
hose was hot.

I would appreciate some ideas on what may be the problem and how I may
diagnose them.

Al Kondo

On Thu, 30 Dec 2004 19:06:52 GMT, (Al Kondo) wrote:

>I have a 96 Sentra with a 1.6 liter engine with 120k miles.
>Recently, I have had an overheating problem. It occurred on a trip
>to Florida (from Texas). I handled it on the trip by turning on the
>interior heater. Fortunately, it was pretty cool outside and the
>heat on the inside was beneficial.
>
>Thinking the problem was the radiator, I brought it to a shop
>yesterday. The tech there did some flow tests and indicated that he
>didn't think that the radiator would have caused the problem I
>experienced. I also checked the thermostat by placing it in some
>boiling water to see if it functioned correctly..... it did. After
>reinstalling the radiator and the thermostat, I ran the car today in
>the garage to see if the overheating continued. Here is what I
>found:
>
>1. the fluid was boiling in my overflow container, while the temp
>gauge read in the middle range.
>
>2. the lower hose from the engine to the radiator was cool to the
>touch after running the engine 10 minutes in the garage. The upper
>hose was hot.
>
>I would appreciate some ideas on what may be the problem and how I may
>diagnose them.
>
>Al Kondo

On *most?* cars, flow through radiator is top down. IOW, hot engine
coolant is pumped through thermostat into TOP of radiator, cool
returned to engine through lower hose.

Lower hose therefore _should_ be cooler than top radiator hose, unless
you have one of those *funny cars* where things are reversed ;-|

Problem is, water is -not- circulating through your radiator _core_
otherwise you wouldn't have *bubbling* coolant in your degass bottle.

You have a plugged radiator, IMHO. And that is why you're
overheating, no?

Lg

You might have this checked for a bad hd gasket, which can pressurize the
cooling system and prevent proper flow.
"Al Kondo" > wrote in message
...
>I have a 96 Sentra with a 1.6 liter engine with 120k miles.
> Recently, I have had an overheating problem. It occurred on a trip
> to Florida (from Texas). I handled it on the trip by turning on the
> interior heater. Fortunately, it was pretty cool outside and the
> heat on the inside was beneficial.
>
> Thinking the problem was the radiator, I brought it to a shop
> yesterday. The tech there did some flow tests and indicated that he
> didn't think that the radiator would have caused the problem I
> experienced. I also checked the thermostat by placing it in some
> boiling water to see if it functioned correctly..... it did. After
> reinstalling the radiator and the thermostat, I ran the car today in
> the garage to see if the overheating continued. Here is what I
> found:
>
> 1. the fluid was boiling in my overflow container, while the temp
> gauge read in the middle range.
>
> 2. the lower hose from the engine to the radiator was cool to the
> touch after running the engine 10 minutes in the garage. The upper
> hose was hot.
>
> I would appreciate some ideas on what may be the problem and how I may
> diagnose them.
>
> Al Kondo

>1. the fluid was boiling in my overflow container, while the temp
>gauge read in the middle range.

Was the water actually at boiling temperature? It is possible that
a failed head gasket could be pumping air in to the system which would
come out in the overflow bottle and "blow bubbles" in the bottle.

>2. the lower hose from the engine to the radiator was cool to the
>touch after running the engine 10 minutes in the garage. The upper
>hose was hot.

Thats not necessarily a bad thing. the water flows in the top and out
the bottom of the radiator so if the radiator is working properly then
this is the what you would expect (although I wouldnt really expect
the lower hose to be as cool as you describe). The two big things for
the radiator is to be able to flow enough water and to be able to
dissipate the heat from that water. Usually the tubes inside the
radiator get clogged up and dont allow enough flow. In some
enviornments the fins on the radiator can get eaten away and cause the
raditor to not be able to dissipate the heat even if it is flowing
properly.

>>I would appreciate some ideas on what may be the problem and how I may
>>diagnose them.

Did your overheating problem occur at highway speed? Were the cooling
fans running? Can you test the temp of the boiling water in the
overflow tank (sneak the wive's meat thermometer out there to test
it).

Steve B.