I recently changed my thermostat due to a low temp reading and seemingly taking a long time to warm up, I also changed both coolant temp sensors at the same time. Temp needle now sits dead on 90 within 2 miles, however out of curiosity I tested the old thermostat in a pan of boiling water and as far as I can tell it looked to be opening and closing normally so I'm left wondering could a faulty temp sensor have been causing the gauge to under read? If so which one?
