How to Replace a Thermostat on an Audi 2.8

1. Place a floor jack under the transmission cross member and jack the front of the Audi off the ground. Place a jack stand on each A-Arm and lower the vehicle onto the jack stands. Make sure the emergency brake is in place or a wheel chuck is placed behind the rear tires to prevent the vehicle from rolling backwards while you work on it.
2. Place a drain pan under the petcock of the radiator and drain the radiator fluid into the pan. Depending on the age of the Audi, the petcock may be hard to open due to exposure to road dirt and salt over the years. Use a pair of pliers but be cautious as the valve easily breaks if excessive force is used. Once the fluid drained, close the petcock.
3. Trace the lower radiator hose from the radiator to the location where the hose connects to the engine. The location is to the right of the engine crank and may be difficult to see from under the vehicle. Depending on your comfort level, you may want to complete the rest of the job from the top of the engine, not the bottom.
4. Remove the radiator hose from the thermostat cover by squeezing the two metal tabs located together on the retention band clamp. A pair of needle-nose pliers is suggested for this task. With the tabs squeezed together, pull the radiator hose off the cover.
5. Remove the two bolts that secure the cover to the engine block with a boxed-end wrench. Unfortunately, there is not enough room for a ratchet. To remove the bolts, make short quarter turns of the wrench, as that is all that is possible in the limited space. With the bolts removed, pull the cover off the engine block.
6. Remove the gasket O-ring that fits into the bottom of the thermostat cover. If the cover does not have an O-ring, inspect the engine block for it. It sometimes sticks to the engine block.
7. Pull the thermostat out of the engine block. Take note that the end with the pin sticks out of the engine block. Place the new thermostat into the engine block so it sticks out in the same manner.
8. Place the thermostat cover back over the thermostat and thread the bolts in as far as you can with your fingers. Tighten the bolts with a boxed wrench.
9. Reattach the lower radiator hose to the thermostat cover. It helps to slide the clamp backwards on the hose and then push the hose onto the cover without the clamp. Then use the pliers to squeeze the tabs and slide the clamp into place.
10. Fill the radiator with a 50/50 mix of radiator fluid and distilled water.