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The article below describes how I replaced the thermostat on my Audi S2 Coupe. At the same time, the thermostat housing feed hose was also replaced due to its poor condition.

No responsisbilty is accepted for anyone attempting this procedure by following the steps contained in these pages. This is intended as a guide only and all usual precautions should be heeded when attempting work on a motor vehicle. I cannot be held responsible for any damage sustained as a result of using these pages.

Replacement parts needed are as follows:

1. Thermostat 069 121 113
2. Thermostat O-ring N 901 368 02
3. water hose 034 121 063 C

Tools needed are as follows:

1. Phillips head (cross head) screw driver
2. Flat blade screw driver
3. 7mm socket / spanner
4. 13mm socket / spanner
5. 10mm spanner / socket
6. Torx bit T30
7. G 00 2000 Hydraulic Fluid
8. "G12 plus" coolant

To make this job easier, I raised the car on ramps. This allows easier access to the underside of the radiator and some of the fittings, particularly the under engine cover. First step is to raise the bonnet of the car. You may want to consider disconnecting the battery. When the bonnet is open, the courtesy light in the boot comes on. Disconnecting the battery will prevent the current drain. An alternative is to pull fuse #4 from the fusebox.

With the car up on ramps, remove the under engine cover. This is held on by 7 fittings. There are 3 flat headed screws under the gearbox to undo. In each of the wheel arches, there is a 10mm plastic nut and plastic lock with a slot which rotates 90 degrees to release. With the fittings removed, the tray can be lowered down. Beware of this clip at the front of the bumper. The tray has to be pulled towards the front of the car to clear this clip.

Remove the 4 screws arrowed using a cross headed screw driver
and remove the top cover and store to one side.

Remove the two 10mm nuts which secure the fan wiring to the
rear of the fan. Take careful note of the colour of the wiring
and do not allow the wires to come into contact with each other
or anything else.

The T30 torx bit can be used to loosen this bolt
located on the front bracket. Do not completely
remove at this stage

Undo the clips from the two top radiator hoses
using a flat bladed screwdriver. The nut arrowed
(1) should be loosened with a 10mm socket. Once
removed, the Torx bolt on the front bracket which
was previously loosened can be taken off
and the securing bracket removed from the car.

The clip on the small hose which feeds the
expansion tank can be opened using a pair
of tile cutters.

Working underneath, undo the securing nut (arrowed)
with a 13mm spanner and the hose clip on the small
hose. This hose comes from the expansion tank
With the hose clip undone, remove the hose. Have a
container ready to catch the coolant which floods out.
Good luck catching it as mine ended up all over the garage floor.

Still under the car, undo the wiring connector from
the radiator fan thermoswitch. These are also secured
to the radiator by a tie wrap higher up (not in the
picture). Undo this tie wrap so that the wiring is
completely free. Also take the opportunity to
remove the lower cowling which can be seen in the
edge of this picture. The two screws arrowed can
be removed by the cross headed screwdriver or a 7mm
socket. There are also two additional fasteners,
not seen here. A 10mm plastic nut and a 10mm bolt.

Undo the two screws arrowed. These secure the side cowling
to the radiator. Probably best to use a 7mm socket on these
screws as access is difficult. Access can be improved by
removing the 3 screws on the expansion bottle and lifting
it out of the way. There is also a 10mm nut holding the
cowling to the wing. Slide the cowling forwards to give
access to the side radiator mounting seen in the next
picture on the right. This nut can be removed using a 13mm

Undo this arrowed bracket using a 10mm spanner and socket.
Once off slide the mount along the pipe to the right hand
Undo the clips arrowed on the picture right. With the power steering clip off, the pipe can be folded upwards on the right of the engine bay out the way. Remove the hose from the thermostat housing and also undo it from the auxiliary radiator from the front of the engine. It is still attached to the radiator in the bottom corner but do not remove this clip. With all hoses off, the side cowling nearest the engine can be bent inwards and the power steering hose and thermostat housing pipe can be pushed through.

With the cowling clear of the pipes, the radiator with fan
can be lifted out.It's fairly awkward and you may have to
adjust the side cowling past the alternator as you lift it.
With the radiator out, the thermostat housing bolts and the perished water hose can be seen right. The two bolts are 10mm and can be extremely tight. Take extreme car when undoing these bolts. If one of them breaks, a new cylinder head may be required. The hose was extremely difficult to remove and ended up being cut to free it. This is not recommended as there is no going back.

The old thermostat was prised out carefully and a new one installed along with a new hose as shown.

Once done, everything has to be reinstalled in reverse order.
The following points should be noted

1.The thermostat housing bolts should only be tightened to 10 Nm.
2. Refill the hydraulic fluid reservoir with G 00 2000. DO NOT USE ATF!!!
3. Fill the expansion tank with premixed G12+ / water (I use 50/50).
4. Turn heater controls to hot and start engine - check for leaks.
5. Loosen bleed valve on top of radiator and close when fluid escaping has no bubbles
6. Top up expansion tank to minimum mark after fan has activated twice.