1. Drain some of the coolant so it comes below the level of the thermostat housing
2. Raise vehicle
3. Remove lower front engine splash tray or panel for access.
4. Disconnect the lower heater return hose from housing by sliding metal clamp back down the heater hose at lower hose connection and pull the heater hose off the fitting on thermostat housing. Allow coolant to escape and drain into a drain pan under vehicle.
5. Unbolt 4 Torx-headed thermostat housing and mounting plate bolts, (two to 10mm, and two to 27mm - long bolts), remove, and lift and discard old rubber gasket if so equipped - if there is still the plastic water outlet hose between them, it MUST be replaced!
1996-1997 Audi A4 Thermostat
The thermostat is located by the water tube assembly. Follow these steps to take it out:
1. Drain coolant down below water thermostat location and disconnect electrical connection at engine coolant temperature sensor on thermostat housing
2. Raise and safely support vehicle; remove upper engine mounting brackets, right wheel
3. Carefully pry clamp to separate water tube -to-cylinder head and upper radiator connecting hose
4. Remove cylinder head cover
5. Remove engine upper timing belt cover at cam timing belt end using suitable small pry bar at cover seam near engine oil filler/breather assembly
