Hello,
So, I've had some issues with Dex-cool gumming up my cooling system to the point where the temp needle was off the high end for 5 minutes of driving.
I've since had the coolant system flushed (and filled with green) and the heat blows fine and the engine seems to be operating normally, but the temp needle only reads 155 degrees when normal temp should be 210 degrees.

I assume the rust goo did something to either the temp sensor or the thermostat, but have no idea which. I'm willing to do both, but with winter's short days I'm hoping its just the sensor.

What do you think? Sensor or Thermostat? Thanks in advance!

 

My vote is the thermostat. Just changed out my cousin's thermostat and it "fixed" the temp sensor. Although, before I did that I changed out his heater core and still had no heat until I changed out the thermostat.

 

This old, but just to follow up, I changed the thermostat and radiator cap and that fixed it. 2 easy and cheap fixes.

 

As we have discussed before, air getting into the system is the main reason for DexCool sludge (or believing that it can actually go '5 years or 100,000 miles' .)