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How to change engine thermostat on AUDI A6 Avant (4B5, C5) – replacement guide
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Recommended replacement interval for the part category Thermostat : 50000 km
Important!
This replacement procedure can be used for:
AUDI A6 Avant (4B5, C5) 1.8, AUDI A6 Avant (4B5, C5) 1.8 T, AUDI A6 Avant (4B5, C5) 1.8 T quattro, AUDI A6 Avant (4B5, C5) 1.8 T quattro, AUDI A6 Avant (4B5, C5) 1.8 T, AUDI A6 Avant (4B5, C5) 1.8 … View more
The steps may slightly vary depending on the car design.
AUDI A6 Avant (4B5, C5) 1.8, AUDI A6 Avant (4B5, C5) 1.8 T, AUDI A6 Avant (4B5, C5) 1.8 T quattro, AUDI A6 Avant (4B5, C5) 1.8 T quattro, AUDI A6 Avant (4B5, C5) 1.8 T, AUDI A6 Avant (4B5, C5) 1.8 … View more
The steps may slightly vary depending on the car design.
This video shows the replacement procedure of a similar car part on another vehicle
All the parts you need to replace – Thermostat for A6 Avant (4B5, C5) and other AUDI models
Thermostat
Alternative products

Wire brush
All-purpose cleaning spray
Electronic spray
Sealant
Torque wrench
Combination spanner #10
Combination spanner #13
Combination spanner #17
Combination spanner #46
Drive socket # 10
Drive socket # 13
HEX bit No.H5
HEX bit No.H8
Ratchet wrench
Funnel
Fluid container
Pincers
Fender cover
Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). AUTODOC experts recommend:
- Check the condition of the coolant every time you replace the thermostat. Change the coolant if necessary.
- All work should be done with the engine stopped.
Carry out replacement in the following order:
- Step 1Open the hood.Step 2Use a fender protection cover to prevent damaging paintwork and plastic parts of the car.Step 3Unscrew the engine cover fastener. Use HEX No.H5. Use a ratchet wrench.
- Step 4Remove the engine cover.AUTODOC recommends:Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Do not use excessive force when removing the part as this may damage it.
- Step 5Unscrew the coolant reservoir cap.
- Step 6Prepare a container for fluids.
- Step 7Clean the coolant hose. Use all-purpose cleaning spray.
- Step 8Disconnect the coolant pipe retaining clip.
- Step 9Detach the coolant hose.Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Professionals recommend:Caution! Coolant may leak out of the coolant lines and thermostat housing.
- Step 10Drain the coolant from the engine.Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Tip:Caution! The coolant can be very hot.Wear gloves to prevent contact with hot liquid.All work should be done with the engine stopped.Wait until the coolant has completely flowed out of the drain hole.
- Step 11Clean the coolant hose. Use all-purpose cleaning spray.
- Step 12Attach the coolant hose.
- Step 13Connect the coolant pipe retaining clip.Step 14Clean the coolant hose. Use all-purpose cleaning spray.
- Step 15Pull aside the V-ribbed belt tensioner pulley. Use a combination spanner #17.
- Step 16Remove the V-ribbed belt.Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Tip from AUTODOC:Check the condition of the tensioner pulley and idler pulley. Replace them if necessary.
- Step 17Return the tensioner pulley to its initial position.
- Step 18Remove the battery cover.
- Step 19Unscrew the fasteners of the car battery terminals. Use a combination spanner #10.
- Step 20Remove the battery terminals.
- Step 21Loosen the alternator fasteners. Use HEX No.H8.
- Step 22Unscrew the fastener of the viscous fan clutch. Use a combination spanner #46. Use HEX No.H8.
- Step 23Loosen the alternator fasteners. Use HEX No.H8.
- Step 24Remove the alternator.
- Step 25Disconnect the alternator connector.
- Step 26Unscrew the alternator power cable fastener. Use a combination spanner #13.
- Step 27Clean the thermostat housing. Use all-purpose cleaning spray.
- Step 28Unscrew the thermostat housing fasteners. Use a drive socket #10. Use a ratchet wrench.
- Step 29Remove the thermostat housing.AUTODOC recommends:Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Do not use excessive force when removing the part as this may damage it.
- Step 30Remove the thermostat. Use pincers.Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Tip:Do not apply excessive force when removing the part. Otherwise you may damage it.Caution! Coolant may leak out of the coolant lines and thermostat housing.
- Step 31Clean the thermostat housing mounting seat. Use a wire brush. Use all-purpose cleaning spray.
- Step 32Install a new thermostat.AUTODOC recommends:Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Do not use excessive force during installation. This may damage the part.Step 33Treat the thermostat housing. Use a sealant.
- Step 34Install the thermostat housing.Replacement: engine thermostat – AUDI A6 Avant (4B5, C5). Tip from AUTODOC:When installing, do not use excessive force to avoid damage to the part.
- Step 35Tighten the thermostat housing fasteners. Use a drive socket #10. Use a torque wrench. Tighten it to 6 nm torque.
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