Hello all.

I have read many forums about the ECT, but can not figure this one out; I recently purchased a 2002 Audi TT to tinker with- It had slight front end impact and radiator + fans were damaged (previous owner); so I got it at a steal and towed it to the garage

Since I purchased it, We:

• Installed a new fan housing,
• new Auxiliary pump,
• new radiator,
• new coolant lines---
• and filled the coolant---

As soon as the car fires up, and within 5-10 seconds (even on a completely cold start) , the temp gauge shoots to H, temperature warning symbol on dash, cooling fans turn on--- and after a 10 min of idling, still no heat---- which I'm thinking air pocket

• CEL did turn on with only one code: coolant temperature sensor circuit High--- replaced with another coolant sensor that was used, (but came from a parts TT that had no issues) --- and still gauge jumps- to H almost immediately.--
• to add, car idles perfectly, with no other issues (misfires, coolant mix in oil etc) ---
• I did not notice any frayed wires on the 4 pins and no other known wiring issue

I am going to get new sensor to install, and hopefully that resolves the issue, but would a bad thermostat cause this? Any suggestions?