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Tools required:

  • TX25 torx screwdriver (to remove rear panel)
  • 3/8" socket set with a short extension bar
  • 13mm socket for above
  • E12 socket for above
  • 22mm ring (or conventional) spanner

Parts required:

  • Standard or aftermarket exhaust (ensure it will fit your turbo manifold!)
  • Exhaust Studs (smart part code: Q000 7105 V000 0000 00)
  • Exhaust Nuts (smart part code: Q000 5805 V000 0000 00)

To remove the exhaust, you need to start off by removing the rear panel and the crash bar.

Looking at the back of the car, you will see that the exhaust system is fully accessible. Note, if you have a mk1-3 fortwo 450, you won't have a lambda sensor in the top of the exhaust. This is sensor is shown arrowed in the following picture:

To disconnect the sensor, trace the wiring up to its connector. You will find that this is clipped in to the wiring ducting, so simply unhook this and unplug. If the connector is dangling loose, make sure that you clip it back to the wiring ducting when you come to refit the exhaust. This will prevent the wiring from burning on the side of the exhaust.

The exhaust is fastened to the turbo manifold with two 13mm nuts shown as follows. Note, if you have a 698cc fortwo, you will have the catalytic converter preheater valve in the way of the rear nut. This can be accessed with a creative combination of socket extension bars and universal joints!

Carefully undo both nuts with your socket set. Be careful when you do this as the studs are prone to snapping off in the turbo manifold. If you think you need to apply excessive force to get the nut to move, try soaking the nut and stud in Plusgas (or similar). This is a highly effective penetrating fluid that should ease stubborn nuts. However, for reasons explained later, this might not work! If the stud comes out of the turbo, don't worry as we will be replacing these later.

With the turbo end disconnected, the only thing holding the exhaust to the car is the centre bracket. Look under the car to see where it mounts to the gearbox with two E12 bolts. We advise undoing this after disconnecting the turbo end to avoid putting excess strain on the above studs.

The exhaust will now be free.

With the exhaust off the car, use the 22mm spanner to unscrew the lambda sensor. With the heat cycles that the exhaust is subjected to, this might require some 'gentle' persuasion. If your exhaust has failed due to a damaged catalytic converter, you might consider replacing the sensor as it may be damaged.

If the sensor is ok, retain it and fit it to your replacement exhaust.

Take the new exhaust and fit the lambda sensor. Tighten this to 50Nm.

Take a new pair of turbo studs and screw the short threaded end into the turbo manifold. Tighten these to 8.5Nm (9Nm if you have 698cc).

Note that you should always use try and use new turbo studs when changing the exhaust. If you look closely at the replacements, the brass nuts are slightly oval. They deform as you turn them onto the stud, making them a one time fit! If one stud is stuck fast in the turbo, leave it. Don't try and force it out.

Bring the new exhaust up into position and attach on its mountings. Some exhausts also provide an additional mounting bracket which bolts onto the gearbox using same bolts used by the bracket for the turbo inlet pipe.

Ensure the exhaust fits nicely onto the turbo. Do up the mounting bolts firmly, but not tight. Put the nuts onto the turbo studs and tighten to 30Nm.

Tighten the mounting bracket that attaches the exhaust to the gearbox up to 23Nm.

If you have a 698cc fortwo, you will have the added complication of the catalytic converter preheater system as described above. Do your best with a universal joint on your socket set when doing up the exhaust nuts.

Plug the lambda sensor back in, and run the engine to check the exhaust is suitably mounted with no signs of leakage.

If all is good, then replace the rear crash bar and rear panel.

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