Hello,
My '98 S70 turbo is having wierd cooling problems. It started with a check engine light a month ago. Hooked it up to the computer and it diagnosed a bad engine coolant temp sensor. Replaced the sensor and things were fine for the next 700 miles. Then last week the check engine lite came back on.

So here is what is happening now:

---It didn't register a bad sensor but it said the coolant temp was 302 degrees F. Now the radiator fan comes on instantly and stays on after the engine is off.
---There doesn't seem to be a good flow of coolant coming out pass the thermostat , so I removed it .
---The bottom radiator hose never seems to get warm.
---I replaced the water pump and timing belt.
---I replaced the thermostat twice(first with a stant, second with a volvo)
---I replaced both radiator hoses.
---with hoses and water pump off.....flushed every opening with high pressure water hose in both directions.

With the thermostat in place, the upper hose never seems to get coolant flowing thru it. I have actually got the car up to temp and removed the upper hose and nothing comes out. Also, when this started the temp gauge fluctuated quite a bit(going up all the way, then dropping all the way down).[:@]

The dealer and a local garage seem to be puzzled by what's going on. NOt sure if there is a special way to bleed the air out of the system either.

thanks!

 

Either the Water pump isn't moving the coolant or the thermostat is bad.

 

just had both items replaced......t-stat is from volvo. finally got coolant to flow with the t-sta removed . I will put in back in. Radiator fan comes on instantly (even when engine is cold) and stays on for up to 5min after it is shut off.

 

Then the new sensor might be fried.

 

Is there any way to test the engine coolant temp sensor with a meter?

 

You can OHM it but I don't have the chart avalible to post it.