1. Check up a condition of rubber pillows of a suspension bracket of system OG. Make sure they are not broken, cracked or otherwise damaged. Replace pillows if necessary.
2. Check the tightening of the bolts securing the exhaust pipe to the exhaust manifold (35 Nm), as well as tightening the bolts for fastening the exhaust pipe suspension bracket to the gearbox (25 Nm).
3. Plug the exhaust pipe opening with the engine running. The engine should stall after a short period of time. If the engine does not stall and a hiss is heard, then the exhaust system is leaking.
If the operation of the exhaust system is accompanied by sounds that are duller than usual, or if, while driving, «coasting» system «shoots», then this indicates that the pipes of the exhaust system are rusted.
Workshops usually prefer to change the entire exhaust system as a set. We do not recommend doing this, because all parts of the exhaust system can be purchased separately and replaced if they fail, provided that the entire system does not require replacement. Therefore, before changing the exhaust system, inspect it to make the right decision.
Muffler welds are the most susceptible to corrosion.
4. Tap the mufflers on all sides with a hammer, and then, pressing with a screwdriver, make sure that the metal has not rusted and the muffler can still be used. If a clear sound is heard when the muffler metal is struck, then the part is normal. Deaf sounds indicate that the upper metal shell of the muffler is quite corroded and it is possible that after a while it «sprinkle», especially in winter, when the roadway is covered with a salt-containing mixture.
When replacing the exhaust system, it is mandatory to change to new appropriate gaskets and self-locking nuts.
Attention! To ensure that the nuts and bolts can be loosened without any problems during the next dismantling of the exhaust system, it is recommended to lubricate their threads with copper powder grease. The same applies to docking sleeves, the inner surfaces of which are also recommended to be lubricated with the indicated agent.
In order not to break the fingers on which the exhaust pipe is attached, when unscrewing firmly seated rusted nuts, it is recommended to first apply a rust converter and let it work. It is even easier to break the nut with a chisel. Nuts are usually made of soft metal (see arrows in illustration 2.0). When installing the exhaust pipe, replace the old nuts with new ones of the same specification. The tightening torque of the nuts on the fingers of the front pipe is 35 Nm.
5. Remove the lambda probe. It must be removed when replacing the catalyst.
6. To do this, release the lambda probe power cable from the mount on the body and disconnect the plug.
7. Turn out a lambda probe.
8. Lubricate the lambda probe before installing it in place with G5 grease, which is part of the repair kit. Do not allow grease to get into the slot on the probe body. The tightening torque for the lambda probe is 50 Nm.
9. Unscrew nuts of fastening of a docking flange of a reception pipe and the catalyst. This flange is usually triangular in shape (see illustrations 2.0a and 2.0b).
10. Turn away nuts of fastening of a connecting flange. Be careful not to let the O-ring fall out.
11. Follow the procedure for reinstalling the springs and inserts on the exhaust system for six-cylinder engines.
12. Install the mating flange so that both halves are parallel to each other (see illustration 2.0c).
The tightening torque of the mating flange bolts is 25 Nm.
The clamp for fastening the junction of the intake pipe and the main muffler is made in the form of a connecting sleeve, into which the pipes to be connected are inserted from both sides, with clamping clamps also at both ends. Such a connection of pipes is quite easy and convenient to use.
Attention! The collar of fastening of a joint of a reception pipe and the main muffler cannot be established repeatedly. The clamp must be replaced even if the nut of only one clamping clamp is unscrewed.
13. Remember the mounting position of the clamp before disconnecting it (see illustration).
14. Unscrew the nuts of both clamping collars. Apply a rust converter if necessary. If necessary, the bolts can be cut or the nuts can be broken with a chisel. The tightening torque of the clamping collar nuts is 40 Nm.
15. Mark or note the mounting position of the tie-down brackets before disconnecting and removing them (see illustrations 2.15 and 2.15a).
16. Turn away nuts of tightening brackets. Be careful not to let the O-ring fall out.
17. When reinstalling the tie-down brackets, make sure that they are in the same position as they were before removal and that they are well «sat down» to a fixed joint. The tightening torque of the bracket nuts is 25 Nm.
Exhaust silencers for Quattro vehicles
The main and additional mufflers in Quattro vehicles are interconnected by a continuous pipe. Mufflers can be replaced individually. To do this, the connecting pipe must be cut. Illustration 2.0d shows the procedure for disconnecting mufflers on Quattro vehicles.
18. Cut the pipe while holding the saw at a right angle. It is practically impossible to cut the connecting pipe of the mufflers in Quattro cars without dismantling the mufflers due to difficult access.
19. Disconnect the main and additional mufflers.
20. Connect the pipes of the main and additional silencers with a clamp, which is used to connect the exhaust pipe and the main silencer (see illustration 2.13). The tightening torque of the clamp bolts is 25 Nm.
Exhaust pipes and mufflers installed with tension can cause knocking while driving.
21. Install the pipes and mufflers on the retaining tabs and align them properly before tightening the mounting bolts.
Attention! All parts of the exhaust system must be located at a sufficient distance from the bottom, providing access to the body. Exhaust pipe (exhaust pipes) additional muffler must be equally spaced around the entire circumference from the edges of the corresponding cutout in the rear bumper (see illustration 2.0e).
22. Tighten the bolts of the downpipe bracket on the gearbox with a torque of 25 Nm, avoiding the tension of the bracket
23. Observe offset tension. On Quattro vehicles, the suspension loop on the rear of the main muffler must have an offset tension of 710 mm. The suspension loop of the front part of the additional muffler for diesel engines must also have an offset of 7 mm. For front-wheel drive vehicles, the rear exhaust system mounting bolt must protrude from the rubber cushion by about 10 mm. When the engine warms up to operating temperature, the suspension of the exhaust system expands and the system is leveled, assuming a vertical position (see illustrations).
24. Rotate the locking bar on the rings on which the pipe and muffler suspension loops are hung, approximately 90°. Make sure the ring is not jammed (see illustration).
25. Tighten, starting with the exhaust pipe of the mufflers, all the bolts of the exhaust system with the specified tightening torques.
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