Note: In order to make it easier to remove the bolts during subsequent work on the exhaust system, the threads must be lubricated with graphite grease. Clamping sleeves also separate from the pipe more easily if their inner side is treated with graphite grease.
Separation of the exhaust pipe from the exhaust manifold
The spacer bolts on which the exhaust pipe mounting nuts sit are easily broken if you try to unscrew a badly rusted nut without pretreatment.
Therefore, before work, the nuts of the connection should be treated with a spray to remove rust or (often even better):
Cut the nuts off with a sharp chisel. As a rule, they consist of a very soft material with an embedded threaded part. The threaded part will then be needed separately «knock off» from the thread of the expansion bolt.
Separation of the exhaust pipe from the exhaust manifold
New nuts from «exhaust system mounting kit» also consist of this «soft» material. So don't use any other nuts from your home collection.
Tightening torque: 30 Nm.
In 6-cylinder vehicles with four-wheel drive, the right catalytic converter (3) attached to the left (1) with triangular flange without spring. Rigidity of connection is reached at the expense of a metal sealing ring. It is necessary to ensure that the cheeks of the flange are parallel to each other. Only with such a triangular flange (2) springs are provided to allow only slight movement of the exhaust system. A metal o-ring is also installed here.
On vehicles with a 4-cylinder engine, the triangular flange connection (arrow) also tough. And here you should pay attention to the sealing ring, the flanges should also be parallel to each other.
The double pipe clamp is replaced after a single bolt connection is loosened.
When installing the clamp (arrow) ensure correct installation (horizontally and vertically).
Removing the lambda probe
Lambda (oxygen) - the probe must be removed when replacing the catalytic converter (or the probe itself).
Hang the cable mounts at the body, separate the plug connections (view the wire along its entire length).
Unscrew the probe.
When installing the lambda probe, it must be lubricated with G 5 lubricant from the Audi workshop kit. In this case, the lubricant must not get into the slot of the probe body.
Tightening torque: 50 Nm.
Loose triangular flange
The double pipe clamp perfectly connects two pipe sections to each other, while allowing them to be easily separated. Important: the double clamp for fixing the pipe cannot be used a second time. It must be replaced after the weakening of a single bolted connection.
Note the position of the bracket for later installation.
Loosen the connections on the double pipe bracket; before doing this, treat the thread with a rust remover.
If it is still not possible to separate the connection, then the bolt/nut must be separated using a cutting machine.
Another possibility is to cut the nut off with a chisel.
Tightening torque for connections: 25 Nm.
For front wheel drive models, the main muffler rear suspension should be preloaded to approximately 7mm (with a cold exhaust system). Number «2» points to the clamp.
On 4WD models, the front main muffler retaining tab should be preloaded to approximately 7mm (with a cold exhaust system). Numeric «2» the rear center muffler is marked.
The segment a = 291 mm indicates the area where the main and additional mufflers of the exhaust system in all-wheel drive models should be disconnected from each other.
Removing the clamp
Before you start removing the clamping bracket, you should remember exactly its position for installation: where do the bolt heads point? Is the brace horizontal or vertical?
Watch the sealing gasket - it must not fall to the floor. Hard material may burst.
When installing, make sure that the halves of the bracket well cover the protrusions at the ends of the pipe.
Observe installation position and tighten connections to 25 Nm.
Dismantling the exhaust system
A heavily tightened exhaust system during assembly can cause annoying growling noise. That's why:
Before tightening the screws, hang the exhaust system freely in the retaining loops and align it.
All parts must have sufficient free play between their position and the body.
The tip must have the same distance from the cutout in the bumper throughout.
The mount on the gearbox can be easily tightened with a torque of 25 Nm. Pay attention to the correct assembly of the sleeves and springs.
Pre-tightening the exhaust system to compensate for deformations at elevated temperatures:
For front-wheel drive models, the mounting tab on the rear of the main muffler must be preloaded with 7mm (illustration on next page top left).
On 4WD models, the front main muffler retaining tab should be preloaded to approximately 7mm (illustration on next page top right).
Additionally, check for a model with four-wheel drive and a 6-cylinder engine: the retaining loop of the additional muffler must have 12-14 mm of preload.
The safety lugs of the fastening rings - these are the protruding ends of the fasteners - have been rotated approximately 90°. Make sure that the retaining ring is not pinched when doing this.
Finally, tighten all exhaust screws, starting at the front. Initial tightening torque - see previous sections.
Separation of the main and additional mufflers (only all-wheel drive models)
In the original Audi all-wheel drive exhaust system, both mufflers are connected to each other by a single piece of pipe.
To replace only one muffler, this pipe must be cut.
In order to have no doubts in which place you need to cut, the illustration below shows a segment a = 291 mm.
Saw the pipe with a trimmer, if possible with a slope to the right.
Due to the lack of space under the vehicle, it is almost impossible to saw with the mufflers still installed. It is better to remove both mufflers together.
Even if you need to change both mufflers, you will receive both mufflers separately as spare parts.
In this case, they will be connected with a double bracket for fixing pipes (also available as a spare part) - as already described above.
Bolt tightening torque: 25 Nm.
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