Stumped...

[The Critic]

In the past, it has been common knowledge of Saturnfans.com members that the Resin-tipped Engine Coolant Temperature Sensor on the ’96 Saturn SL2s were quite susceptible to failure. The frequent failure of this part was so widespread, that Saturn later released an updated Engine Coolant Temperature Sensor with a brass tip to solve the problem. The most common sign of failure included an excessively rich fuel mixture after engine warm-up (leading to poor fuel economy), and others that escape me at the moment.

The thermostat, though I’m unaware of any known problems, normally requires replacement as at around 100,000 miles for many vehicles, or at some point in the vehicle’s life. Sometimes, they happened to be “stuck” in the open mode, and lengthened the amount of time for engine warm-up.

(Note: Please feel free to correct me if any of the above information is incorrect.)

My ’96 Saturn SL2 has about 90,000 miles, and has its original thermostat and engine coolant temperature sensor. Two years ago (meaning I’m due for another one this year), the smog inspection yielded an excessive hydrocarbons reading, and as a result, I barely passed the smog inspection.

During the course of this past winter, when I finally started paying attention, I noticed that the coolant temperature gauge barely moves past the ¼ mark…even after the engine is fully warmed up. Today, as the temperature is a blazing 85 degrees, during the same type of normal driving (city), the temperature gauge appears to read normally, showing the coolant temperature to be around 85-90C, with the needle being 1/2cm before the ½ mark.

Initially, I had suspected that my thermostat was stuck open, and was lengthening my warm-up time. However, the engine warms up extremely quickly, the needle will reach just past the ¼ mark within 0.5 miles.

I’m due to perform some work on the car soon, so what should I replace? Should I leave the thermostat and engine coolant temperature sensor alone?

Also, if this helps, the fuel economy is about 22-23MPG…most trips are less than 2 miles.

Thanks in advance.

 

[rshaw125]

Time to replace the thermo. and the temp. sensor.

 

[Earl Filter]

If I was going to do one or the other, I'd do the temp sensor. They're a known weak point. I don't think you can say the same about the thermostats. However, since you'll lose some coolant either way, I'd do a drain and refill on the coolant while doing BOTH of them, as neither are hard or expensive to replace. Here's a pic of me preparing to replace the engine in the '97 SL2 I had for a while. Who needs a cherry picker?

 

[Matt_S]

I'd also recommend doing both. Thermostats are cheap and easy and the sensor is a know weak point. It seems like a no-brainer.

 

[Rhymingmechanic]

I have a 1994 SL1 that did the exact same thing--temperature would never get much above 1/4 on the gauge. I changed the thermostat first, because it was cheaper than the sensor. With the new thermostat, temperature is stable at just about 1/2 in cool weather, moving or stopped. The fan now kicks on between 1/2 and 3/4. It never got hot enough to do that before. I put the old thermostat in boiling water to check it, and it was still open in the garage 2 weeks later.

This year's emissions were much lower than 2 years ago. I'm getting about the same mileage as you with similar driving. Miles per quart of oil is another story.

 

[Mud]

Earl you are my kinda guy - garage FULL of car parts.

 

[ikeepmychevytoo]

^ nice photo

 

[GROUCHO MARX]

Nice legs!