Is my coolant temp sensor bad?

[gt50]

I have a 98 sc2. I have owned it for 2 weeks and put almost 1000 miles on it

Anyway I do a lot of freeway driving. My gas mileage is around 28-30mpg so far, which is great since my wrx only gets 17-19 with premium. I think I should be getting better gas mileage though. I have started do basic tune-up stuff to improve it hopefully.

Well one thing that I have noticed is that the car seems to run very cold. The sensor hovers around the "1/4" tick mark. Should it be closer to the center like most cars, or is this normal? Could this affect gas mileage?

I read in a post somewhere that there are 2 temp sensors that should be replaced at the same time. If this is abnormal I definately want to replace them.

[saturnxsc2]

mine stays around that area.

my mechanic said that there are two thermometers for saturns, one for winter and one for summer. maybe someone can elaborate but he said that you gotta change it twice a year to accommodate the new temperatures outside. supposedly it is an easy repair, but mine hasnt been changed this season yet. maybe someone can elaborate.

[VS1400]

Your 98 SC2 has only one coolant temp sensor. Pre-96 models had two. One for the gauge, one for the computer (a better system, IMO, but oh well)

28-30 MPG doesn't sound to bad for a SC2, but the coolant temp sensor could still be off. Unfortunately, the are prone to failure as the car gets older.

Changing the sensor is an easy job. It's located on the right side of the cylinder head, below and just behind the top radiator hose.

A few tips for changing it: 1) Loosen the coolant reservoir cap to let the pressure out of cooling system. Then re-tighten the cap. This will minimize coolant loss. Have the new sensor in hand ready to install when you remove the old one.

2) Change the sensor when the engine is cold (no burnt hands)

3) Inspect the electrical connector for corrosion on the terminals. If they are green and corroded, you'll need to splice in a new connector as well.

[gt50]

Thanks for the info. The hard part is finding a sensor. I guess I will make a trip to a saturn dealer to pick one up.

Today my sensor seems to have almost died. I drove my wrx all weekend. Today when I drove my saturn I noticed the temp was showing very cold. After a 15 minute run on the freeway it only shows 1/8 (barely above the cold line) Then the SES light came on. I opened the hood to try to find the sensor hoping for a dirty connection or something. I could not find the sensor. After rereading what you said I will look for it again this week. When looking for it tonight with my flashlight I noticed that the engine was wet... I am guessing coolant since it has not rained I will have to investigate this further.

[gt50]

I think I found the sensor Yellow and black wires right next to the water inlet to the engine. I wiggled the connection a little while the engine was running. It went to a little above 1/4 again.

The wetness is oil. Seems I have a leaking valve cover gasket. I will add that to my todo list.

Does anyone happen to know the torque spec for the valve cover? I have broken these studs on three different cars. Now I use my torque wrench religiously for those bolts.

[gt50]

Just to update this thread...

I changed my coolant temp sensor this weekend. It was quick and painless. I did not know I could lose that much coolant so quickly. I bought a new connector also. My old one was corroded. After it was done the car still hovers a little above 1/4 like before, but now when I am not moving the temp gauge moves up to the halfway mark, and a little past halfway the fans kick in. It never moved up before so this is good.

I attempted the first oil change on the saturn since I only bought it a month ago. Overtightened drain bolt, broken nut and $240 later I was not a happy camper. I would like to strangle who ever changed the oil last on the car. I did the change early saturday, so I went to the saturn dealer and got a new pan. Once I figured out I had to remove the crank pulley to get it on, I decided to have it towed to the mechanic monday morning.

Now I am going to spend some money on the subie since it is jealous