Temp gauge reads cold

On a ~100-mile drive, the temperature gauge on our 98 SL2 never went
over about 1/8. The heater seemed to be blowing out plenty of warm air
on us. Does this sound like a bad thermostat, CTS, or something else?

 

chances are it is the CTS for sure. The CTS and the IAT are the same
sensors and I would replace both of them with the new version (brass)
that is available at napa.
should fix the problem

 

Do you have a thermometer to put in one of your dash vents? Turn the
blower on low or medium and at the "vent" setting. Do not run the AC.
Once the engine is warmed up, the air in the vents should be blowing
between 125° and 140°. If not, I would start with the thermostat.
Anything less than 120° will not be sufficient in extreme cold
weather.

James

 

Luckily, we don't have extreme cold weather. But thanks for the tip.
I'll try that out.

 

Let the car idle for a while and see if the temperature gauge climbs up
to the normal 'middle' point. If the indicated temperature climbs up at
idle while standing still but stays low while car is moving forward
through the air, it is probably the thermostat. If so, get a new
thermostat in there soon as a cool engine means cool oil that will not
lubricate very well and the engine wear will be about 10x normal.

 

<< as a cool engine means cool oil that will not
lubricate very well and the engine wear will be about 10x normal. >>

I will never agree with that part of your statement! James

 

In the continuing saga, I drove the car to and from work today with a
meat thermometer in the vent. It read 150°F when I got to work (and
again when I got home). I let it idle in the garage for five minutes or
so, and the temp gauge went up to just under 1/4. If I read this
correctly, neither your test, nor the one suggested by James indicate a
bad thermostat.

Should I take p_vouers advice and go buy a CTS? Is there some other
test I should do to know for sure?

 

If your air temp was 150°, your thermostat is working properly.

Time to buy a CTS. If problem persists, your temp gauge is not reading
properly.

James

 

OK thanks. You said NAPA in your other post. Does NAPA have its own
brass CTS, or was NAPA simply shorthand for "a auto parts store, not
necessarily the dealership?"

 

napa has the brass tip ones.. believe they are made by eichlen or
something like that.

 

The viscosity of the oil blend is established and tested by the oil
manufacturer based on its expected operating temperature. If the
temperature is below that point, the viscosity will be higher and the
oil will not lubricate as well, causing increased (and completely
unnecessary) wear of the engine components. I've seen engines fail
after being operated for 10-20k miles with a leaking thermostat that
should have lasted another 100k miles. On Saturns, the timing chain
will sometimes fail after extended operation at cool temperatures.
Thermostats are cheap so put one in if you need one. I agree with
others, though, that the original poster needs a CTS, not a thermostat.

 

Personally I would purchase from the dealer. But if NAPA or another
store is closer, go for it. Replace the AIT sensor at the same time, I
think they are the same sensor. James

 

I missed the early part of this thread that gave the year of the car...

in OBD1 Saturns ('91-'95) there are 2 temp sensors in the head - a 2 wire,
that is the same as the IAT sensor that goes teh the PCM, and a 1 wire that
only runs the guage. OBD2 )'96-'02) have 1 sensor of the 2 wire variety
that goes to the PCM, which then sends that same signal on up to the guage.
Sooo - if you have a "91-'95, and it is running fine, no rush to replace
that sensor.

 

Thanks for clearing that up. I've been looking for that extra sensor
that is supposed to be the same part as the CTS, with no luck (this is a
1998 model).

By the way, I put in a new brass coolant temp sensor from Kragen (Napa
was closed and Saturn is 80 miles away) last night. Today, the temp
went up to about 1/4 after the engine warmed up. That's more like what
I'm used to. Hopefully that will clear up the cruddy mileage we've been
getting lately, too.

Thanks to everyone for the help. I love this newsgroup!

 

98's dont have 2 CTS's.

A CTS that fools the computer into think it is still cold will run rich.
A rich running engine will also run cooler.

 

that extra sensor is at the front grill area.. that box that holds your
air filter look in fron and below it.. you'll see it attached to the
intake plastic horn that goes to the filter box..
I would replace it also.. for it will influence your milage.
In cool weather my saturn (97) runs just a tad over 1/4 and in the
summer just a tad over 1/2. When my sensor was bad my rpms were also up
when cold around 1500 -1800 now when cold they are at about 1100 then
when she warms up drops to 900

 

OK, _now_ I found it. It's not obviously bad like the (cracked) CTS.
But I'll see if I can get one of those, too.

 

NO. That is the Intake Air Temperature sensor. It is identical to the
Coolant Temperature Sensor.

In '91 to '95 S-series Saturns, there is a 2nd Coolant Temperature sensor
that runs the guage on the dash. It is different that the other 2 sensors,
in that it only has 1 wire coming off of it.