Good day everyone,

I have this coolant leak problem that has been bothering me for months. My a3 has a slight coolant leak problem that requires me to top up the coolant every 3 months. I replaced the 2 hoses on top of the gearbox cooler, changed both t joints, and the leaking seems to have reduced. Changed the coolant temperature sensor near the block coolant flange as the temperature gauge would go nuts. However every now and then when I reverse into parking I would get a small puddle of coolant on the floor. Also the car would take vr long to warm up to operating temp (close to 20 minutes). I have a feeling that a faulty thermostat is causing this. Does it cause the small leakage as well? I scanned with vcds and got no codes. Pressure tested the cooling system too and shows no pressure drop. Would like to ask for any valuable input before taking everything apart this weekend and have the thermostat replaced.

Also the coolant has no engine oil sign, nor the engine oil has any milk shake. I'm assuming this is not a head gasket problem.