I started my car this morning and let it idle as I got ready for work. Came out and pulled out of the driveway. Noticed that it was overheating and the temp light was blinking as well as the SES light. The car also lacked power and the engine runs rough. Would the thermostat cause this or where should I start?

 

Blinking SES means active misfire in 1 or more cylinders. Should be codes stored.

Flashing temp light can mean several things.

Coolant level in reservoir is low. The sensor is built into the reservoir. Even a small level deficiency as measured when cold can trip the sensor.

I believe the light will also be tripped by a very high reading and I mean very high from the coolant temperature sensor mounted in the cylinder head.

Now for some questions to narrow this down.

Where was the temperature on the dash gauge reading while the light was blinking?

I ask this because both of my mid-90s Saturns will have this light blinking for the first 3 minutes after startup when it is very cold out. As the engine starts to warm up, the coolant in the reservoir expands even though the thermostat is still closed.. in the winter I add a slight extra amount of coolant to the reservoir when this begins to happen at it usually takes care of the flashing dash issue.

Do you actually the steam associated with an engine overheating? If you pop the hood, is there an obvious place where the coolant system is not holding pressure? Do you have white smoke out the tailpipe or does it smell sweet?

Does the liquid in the court reservoir look like a milkshake or is it Orange?

Does the oil on the dipstick look like a milkshake?

I am not ignoring your question about the thermostat. Just need to know a bit more before being able to say whether it might be involved.

 

So, no white smoke or obvious steam or milkshake look. But the coolant I put in is orange... I was wondering if the fan was working, so I disconnected the sensor as the car was running and the fan turned on. Does this mean the sensor is bad?
Oil also looks ok.

 

I also have very limited power when accelerating.

 

1) Where was the temperature gauge on the dash reading when you got the blinking temperature light? This is key to the diagnosis.

2)Does the blinking cool light ever go out and does the SES ever stop flashing?

3) to both of these flashing conditions happen immediately at startup?

We are basically trying to determine whether the car was really overheating or not. That can be deduced from several behaviors and sensors.