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Audi A3: How to Replace Thermostat

The thermostat is designed to open up when the engine coolant reaches the optimal temperature to keep it cool. Learn how to replace it here in the Audi A3.

By Bassem Girgis - March 23, 2016

This article applies to the Audi A3 (1996-Present).

The thermostat is a little device that works as a gate in the Audi A3. When the engine starts, the thermostat stays cold, which allows the engine to reach its optimal operation temperature quickly. When the engine reaches the desired temperature, the thermostat opens up to let coolant flow through the engine, which keeps it cool and prevents it from overheating. When the thermostat fails, it could stay closed, even when the engine reaches the desired temperature, which causes the engine to keep heating up, without getting any coolant into it to cool it down. This article will show you how you can replace the thermostat yourself in the Audi A3.

audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
Figure 1. Thermostat.
Audi A3 How to Replace Thermostat

Materials Needed

  • Socket
  • 16mm and 13mm wrench
  • Drain pan
  • Flat head screwdriver
  • Pliers
  • Thermostat

Step 1 – Remove engine cover

Use your flat head screwdriver to remove the screw holding the intake tube to the box. Then pull off the whole cover. It is held in place by a few clamps.

audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
Figure 2. Pull engine cover off.

Step 2 – Remove serpentine belt

Use a 16mm wrench to loosen the belt tensioner, then pull the belt off of the pulleys and out of the car.

audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
Figure 3. Red arrow indicates the tensioner pulley.

Step 3 – Remove the tensioner

To remove the tensioner, remove the three 13mm bolts holding it in place. Pull the tensioner out of the car.

audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
Figure 4. Remove tensioner out of the car.

Step 4 – Remove the alternator

Remove the two bolts holding the alternator in place, then wiggle it to remove it. When the alternator comes loose, remove the electrical connection, then remove the nuts from the wiring harness. Pull the alternator out.

audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
Figure 5. Remove alternator.

Step 5 – Replace thermostat

Using your pliers, slide the hose clamp back, then remove the hose off of the thermostat assembly. Plug the hose with a towel to avoid excessive spillage. Remove the thermostat housing by removing its two bolts. Finally, remove the old thermostat, then install the new thermostat in its place.

  • audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
    Figure 6. Remove hose.
  • audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
    Figure 7. Remove thermostat assembly.
  • audi a3 s3 2.0t coolant radiator thermostat overheat stuck replace remove how to
    Figure 8. Replace thermostat.

Step 6 – Re-install components

Installation is the reverse of removal.

  • Install the hose onto the thermostat assembly, then slide the clamp forward.
  • Install the alternator, then install the electrical connections on the back of it.
  • Install the tensioner pulley.
  • Install the belt.
  • Install the engine cover.

Featured Video: Thermostat Housing Removal

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