[JBarstad]

A bad thermostat won't usually trigger a CEL, it sounds more like your temp sensor is shot. Replacing it is very easy. It's in the purple box in the image above. Just leave the thermostat alone as long as you tightened everything back up again.

An intermittent CEL for a failing sensor would not be unheard of. As the sensor starts to drift it is giving outputs right on the edge of the "acceptable" range. At some point it will exceed those limits, and you'll have a permanent CEL until it is replaced.

 

[Saab06Owner]

Okay thanks! I hope I get this fixed soon

 

[Saab06Owner]

Can you explain how I replace the sensor step by step? Can anyone replace it even if they don’t have much prior knowledge of cars?

 

[aerojon]

A bad stat(stuck open thus overcooling the engine) will trigger a P0116 code...

 

[davmac]

The P0116 criteria indicates that the temperature sensor sees too high or too low a temperature after the car has been driven for 8-10 minutes. If the temp sensor is good (and cooling system has no leaks or compromises) then the fix is always a new thermostat. If this is your only code then thermostat is definitely the right first step.

I have also seen a P0116 return after replacing a thermostat with non-OEM part. A new OEM thermostat cured the problem.

It could be a bad sensor. The sensor screws into the engine at a place where the end of it is in coolant. To remove it just unplug the connector. Then unscrew it from the engine with a deep socket or an open end wrench (if you have access).

To test the sensor outside the car: The sensor is an NTC thermister. The ECU sends a 5 volt reference, and as the sensor resistance changes with temperature the ECU measures voltage drop. You could just measure resistance directly from the 2 connectors with the sensor in water. Heat the water from room temp to boiling. The expected resistance at various temperatures is in the WIS.

 

[Diggs]

The P0116 criteria indicates that the temperature sensor sees too high or too low a temperature after the car has been driven for 8-10 minutes. If the temp sensor is good (and cooling system has no leaks or compromises) then the fix is always a new thermostat. If this is your only code then thermostat is definitely the right first step.

I have also seen a P0116 return after replacing a thermostat with non-OEM part. A new OEM thermostat cured the problem.

It could be a bad sensor. The sensor screws into the engine at a place where the end of it is in coolant. To remove it just unplug the connector. Then unscrew it from the engine with a deep socket or an open end wrench (if you have access).

To test the sensor outside the car: The sensor is an NTC thermister. The ECU sends a 5 volt reference, and as the sensor resistance changes with temperature the ECU measures voltage drop. You could just measure resistance directly from the 2 connectors with the sensor in water. Heat the water from room temp to boiling. The expected resistance at various temperatures is in the WIS.

Sounds like a lot of work for a $10 part.

Simple job.

 

[htowniman]

Hi, I just replaced my thermostat. Do I need to turn the thermostat or just put it there and use the housing to seal it? I was turning the thermostat so long and wonder why it didn't loose, then realized the housing is on the edge of thermostat. I see some people can move the housing on the side, and mine barely move.

My coolant temperature around 176 and little below the half way mark some time. Did I do it wrong?

To remove the third bolt is not hard at all, but I have no way to clean the surface of the housing, unless remove those hose.

 

[htowniman]

I found this write up from FCP Euro parts. It cleared out my question.

How to Replace a Thermostat on a Saab 9-3

It’s generally a good idea to replace your car’s thermostat as preventative maintenance with every major service interval. They are a critical part of your car’s ability to regulate it’s own temperature based on how hard your engine is working at any given time and fluctuating environmental...

blog.fcpeuro.com

 

[okcrum]

You can pull the brake vacuum pump (4 bolts) to get clear access to the thermostat housing for cleaning. If you do, might as well put a new oil seal on that too.

 

[htowniman]

You can pull the brake vacuum pump (4 bolts) to get clear access to the thermostat housing for cleaning. If you do, might as well put a new oil seal on that too.

Yeah, I was thinking about to remove the brake vacuum pump that I replaced 2 years ago. End up, I was too lazy for that. Hope it doesn't leak any coolant.

 

[ConorH]

Hi, I just replaced my thermostat. Do I need to turn the thermostat or just put it there and use the housing to seal it? I was turning the thermostat so long and wonder why it didn't loose, then realized the housing is on the edge of thermostat. I see some people can move the housing on the side, and mine barely move.

My coolant temperature around 176 and little below the half way mark some time. Did I do it wrong?

To remove the third bolt is not hard at all, but I have no way to clean the surface of the housing, unless remove those hose.

Did you ever figure out if it was normal for the temperature to be at 176 and drop slightly below when driving? Mine is exactly the same after fitting an OE tstat..