Exhaust system

From W220 S-Class Encyclopedia
Jump to navigation Jump to search

Exhaust system

Exhaust system for 6-cylinder (M112) gasoline vehicles:
W220 exhaust system 6-cylinder gasoline.png
Exhaust system for 8-cylinder (M113) gasoline vehicles:
W220 exhaust system 8-cylinder gasoline.png

Identifying the components in this diagram with same nomenclature as above:

Part Part no. Image Description
220 / 245 A2024920281 (13 EUR) W220 sealing ring left exhaust pipe to right exhaust pipe A2024920281.jpg

W220 sealing ring left exhaust pipe to right exhaust pipe A2024920281 2.jpg

Sealing ring. Sealing ring. Catalyst to tight fit / Left exhaust pipe to right exhaust pipe
220 / 245 Fa1 142951 (3 EUR) Fa1 142951.jpg Sealing exhaust pipe. Height: 19mm, Inner diameter: 51mm, Outer diameter: 64mm
200 A1264920845 (12 EUR) W220 flange catalyst to rear exhaust pipe A1264920845.jpg Flange. Catalyst to rear exhaust pipe
200 HJS 82007055 (35 EUR) HJS 82007055.jpg

HJS 82007055 2.jpg

Split flange. For pipe diameter of 55mm. Distance between holes: 78mm
210 A1269970041 (6 EUR) W220 sealing ring catalyst to flange A1269970041.jpg Sealing ring. Catalyst on flange
210 Fa1 141955 (2 EUR) Fa1 141955.jpg Exhaust pipe gasket. Height 15mm, Inner diameter 55.6mm, Outer diameter 64.5mm

Exhaust transmission mounts rusted off

Exhaust manifold

Exhaust manifold for 6-cylinder (M112) vehicles:
W220 exhaust manifold M112.png
Exhaust manifold for 8-cylinder (M113) vehicles:
W220 exhaust manifold M113.png

Screening plates

Exhaust system screening plates for 6-cylinder (M112) vehicles:
W220 exhaust system screening plates M112.png
Exhaust system screening plates for 8-cylinder (M113) vehicles:
W220 exhaust system screening plates M113.png

Issues - Exhaust Pipes, Catalytic Converter, Mufflers

  • Occasionally the exhaust system will develop an annoying but quiet rattle. This may be a simple loose bracket, heat shield or clamp.
  • Occasionally the exhaust system will develop an intermittent but very loud rattle. W220's are known to have an issue with the catalytic converters which come apart internally and make a loud rattling sound at particular engine speeds (around 2,500 RPM) and sometimes only when the cat is hot. You may not notice the noise when driving until the failure gets worse and the vibration gets very loud as it is masked by the usual road and car sounds. It is often first noticed when driving around a multi-level parking station where the sound bounces off the close solid walls. M-B issued an eight year / 80,000 mile (125,000 Km) warranty to cover the failed catalytic converters.
  • Some owners have found that it is mostly the rear cats that fail, although be warned, it may be broken pieces in the front catalytic converter being deposited in a rear cat.
  • The video shows a ML55 but is a good example of a noisy catalytic converter at idle speed.

  • A catalytic converter can block sufficiently to reduce exhaust flow which may prevent the engine from developing full power. This issue will usually trip an engine fault code.
  • Catalytic converters must not be disposed of as regular scrap. The catalytic converter contains valuable rare earth metals, which can be recycled.

Tips - Exhaust Pipes, Catalytic Converter, Mufflers

  • Beware that often the rear cat will rattle because it is full of substrate that has broken down in the front cat and simply ended up in the rear cat.
  • If replacing the catalytic converters with after market ones, go with a metal substrate catalytic converter since it will flow much better than a ceramic one.
  • When reassembling a new or repaired exhaust system apply high temperature anti-seize copper grease to all the gaskets, seal rings, flange surfaces, and bolt threads. You will really appreciate having done this next time the system has to come apart.
  • Also cover all exposed bolt threads with silicon to prevent corrosion. The silicon is easily peeled off before undoing the next time. If you have previously used the copper anti-seize grease you will be able to undo the nut by hand.

Parts - Exhaust Pipes, Catalytic Converter, Mufflers

  • OEM catalytic converters cost around $1,200 but cheap aftermarket cats are available for under $300 installed.

DIY Procedures - Exhaust Pipes, Catalytic Converter, Mufflers

Diagnose Blocked Cat.

A good way to make sure a catalytic converter is not blocking is to perform a temperature test.

  • Drive the car for say 20 Km to let the exhaust fully warm up.
  • Put the car up on ramps or a hoist.
  • Start the car and let it idle.
  • Use a temperature probe or preferably an IR non-contact temperature sensor with laser pointer and measure the temperature of the exhaust pipe immediately before and after each catalytic converter.
  • If the before and after temperatures are nearly the same the cat. it is not blocking.
  • If the before and after temperature difference is large the cat. has an internal problem and is blocking.

Diagnose Source of Rattle Noise

  • To investigate an annoying rattle jack the vehicle up and place on stands. (TIP: You may find that When you put the car up on front jack stands only, it will not rattle. One Benz-World enthusiast Had to level out the back of the car to get the rattle going.)
  • Tap the complete exhaust system with a rubber mallet while listening for the rattle. If you are lucky it is often a broken strap or bracket making the noise. If you are unlucky you may have the dreaded internal issue common with the catalytic converters.
  • If the rattle only appears at certain speeds, it is a loose baffle or interior part that is vibrating at its resonant frequency. To find this issue try tapping the rubber mallet at very quick intervals to get the vibration started.
  • A mechanics stethoscope or even an ear listening against a long screwdriver handle can help find a quiet rattle.

Temporary Fix for Rattling Cat.

TIP: Be warned that any warranty will be void if there are dents found on the cats from someone trying to hold in the honeycomb substrate. Not a problem if you exceed the warranty period, but a caution for others with a newer vintage / class of car.

One enthusiast discovered a slight rattle coming from a rear cat. He took a hammer and put a little dent in the bottom of the cat to keep the internals from moving around and making noise.

He was lucky and the honeycomb material was still intact but had just come loose.

He reported after one year that the cats were still rattle free.

Some DIYers have hammered dents in three sides to secure the internals.

Permanent Fix for Rattling Cat. or Cat. Gutting

Be Warned: The material found inside a catalytic converter is toxic and appropriate handling precautions must be used.

Not recommended but a crude fix used by some DIYers for a rear rattling catalytic converter is to gut it. After the front and rear cat assembly is removed from the car, use a long piece of rod, pipe or crow bar to ram through the inside of the rear cat. Constantly shake out any broken pieces and progress slowly. It may take 30 minutes of probing and clearing out to remove most of the internals. Be careful not to distort the outer case or damage the pipes. Once the rear cat. is clear check the pipe between the front and the rear cats. as well.

An illustrated post at [1] by Benz-World member mercy-me shows how to gut a cat. by cutting it open and then sealing with a mechanically fastened metal plate.