Need some help from anyone with good knowledge of Audi A3 2001 1.6 AVU coolant system to help understand why my Audi is not able to cool the coolant temperature. The symptoms are as follows;


- After 15mins ticking over or just under 10mins of driving the temperature gauge on the dashboard starts pushing over 90c and warning light comes on
- Top radiator hose is hot. Bottom hose is cold
- Both fans spin while A/C is turned on but not to cool system (suspect there is no hot water in radiator to trip fans)
- With the coolant cap sealed the reservoir is between Min & Max but the hoses to thermostat and top radiator hose are not pressurised, can easily press them and don't see a change in level of the coolant reservoir level.
- Cold air comes out quickly from internal blower fans, but no pressure for hot air (suspect this is a heater matrix with crud inside and may be separate issue)
- No signs of coolant leakage

Please see my troubleshooting steps so far


- Top hose for coolant reservoir detached into a plastic bottle and revved the engine - good flow on tick over and revving the engine increased flow
=> Water Pump is working


- Drained coolant system and removed top and bottom radiator hoses. Poured 500ml of water through the radiator and all of the water passed through
=> Radiator is not blocked


- Replaced Thermostat and temperature sensor just behind the thermostat (please note this is integrated thermostat, not the type just behind the alternator)
=> Thermostat may be DOA, temperature sensor reads similar temperature to dashboard when checked on channel 49c of climatronic diagnostics


Any suggestions on next steps to find the problem?