Only one catalytic converter on the front-wheel-drive model with a six-cylinder engine (3). Exhaust pipes from both cylinder blocks (2) enter in front of the catalytic converter in one place. Numeric «1» double collar shown.
The six-cylinder engine in the quattro model has two separate catalytic converters (2 and 3). Numeric «1» double collar shown.
Here, the arrow shows a lambda probe screwed into the exhaust manifold in a four-cylinder engine with a displacement of 1.6 liters.
Various rubber suspensions for the exhaust system
Front end silencer suspension in the Audi A4 with front wheel drive.
One of the rear end silencer suspensions in the A4 quattro.
The exhaust system must be straightened without tension
In a front-wheel drive Audi, the front suspension must be preloaded with approx. 7 mm.
In quattro, the mounting loop at the front on the intermediate muffler must be preloaded with approx. 7 mm.
Disconnecting the front pipe and exhaust manifold
1. The spacer studs on which the downpipe mounting nuts are located break off easily if a heavily rusted nut is unscrewed with pressure.
2. Therefore: spray anti-corrosion spray on the screw connection or (often it's better):
3. Break nuts with a sharp chisel. As a rule, they are made of soft material with an embedded threaded helix. After that, the threaded part must be removed separately from the thread of the expansion stud.
4. The new nuts in the exhaust kit are also made from the same soft material. Do not use nuts from home stock. Tightening torque: 30 Nm.
Dismantling the lambda probe
The lambda probe must be removed when replacing the catalytic converter (or the probe itself).
1. Hang the wire brackets on the body, disconnect the connectors (view the wire along its entire length).
2. Unscrew the probe.
3. During installation, lubricate the lambda probe with anti-corrosion grease. In this case, the lubricant must not get into the area of the openings of the probe body. Tightening torque: 50 Nm.
Removing the triangular flange (with spring)
1. Loosen the three screw connections on the connecting flange.
2. If an o-ring is inserted, but special attention must be paid to it - it must not fall to the floor. Hard material may crack.
3. If a gasket is embedded in the flange, it must be replaced.
4. Bolt tightening torque: 25 Nm.
5. When tightening, make sure that the bolts are tightened parallel to each other.
Removing the double tube clamp
The double tube clamp seamlessly connects two cut pieces of pipe and detaches easily. Important: The double tube clamp cannot be used a second time. It must be replaced even after loosening the screw connection.
1. Mark the mounting location of the clamp for reassembly.
2. Disconnect the screw connections of the double tube clamp; to do this, treat the thread with a rust remover.
3. If the screw connection cannot be removed in this way, separate the bolt from the nut with an angle grinder.
4. Another possibility: cut the nut with a chisel.
5. Screw tightening torque: 25 Nm.
Disconnecting the intermediate silencer and end silencer
1. In the original exhaust system, both mufflers are connected by a solid piece of pipe.
2. In order to replace one of the two mufflers, you need to saw through the connecting pipe.
3. In order to be sure about the place of sawing, transfer the length of the pipe of the new muffler to the pipe of the old one. To be sure, leave a margin of about 10 mm. In this case, during installation, there will be little room for adjustment.
4. Cut the pipe with a metal saw as straight as possible.
5. Due to lack of space, it is hardly possible to do this on the installed muffler. It is better to dismantle both mufflers together.
6. Even if you replace both mufflers, you can only buy mufflers separately as spare parts.
7. Connect the pipes with a double pipe clamp as already mentioned (from the spare parts warehouse). Tightening torque: 25 Nm.
Exhaust system alignment
An exhaust system installed with overstretching can cause annoying noise. That's why:
1. Before tightening the screw connections, freely hang the exhaust system in the mounting loops and straighten:
2. All parts must be at a sufficient distance from the body.
3. End silencer (mufflers) on all sides must be at the same distance from the edges of the cutout in the bumper.
4. Tighten the bracket on the gearbox with a tightening torque of 25 Nm. Pay attention to the correct assembly of the sleeve and spring.
5. Pre-tensioning the exhaust system to ensure balanced thermal expansion:
6. For Audi with front wheel drive, the front suspension of the intermediate muffler must be preloaded with approx. 7 mm.
7. In quattro, the mounting eye at the front of the intermediate muffler must be preloaded with approx. 7 mm.
8. In the end, tighten all screw connections of the exhaust system, starting from the front. The tightening torques are given in the previous sections.
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