Exhaust system: Difference between revisions

Latest revision as of 10:45, 26 August 2023

Exhaust system

Exhaust system for 6-cylinder (M112) gasoline vehicles:

Exhaust system for 8-cylinder (M113) gasoline vehicles:

Catalytic converters, exhaust pipes

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

Part	Part no.	Description
10	A2204908519	Catalytic converter. Front left (M112)
30	A2204908619	Catalytic converter. Front right (M112)
10	A2204907519	Catalytic converter. Front left (M113 facelift)
30	A2204907619	Catalytic converter. Front right (M113 facelift)
10	A2204904119 BM BM90841H KLARIUS 323015	Catalytic converter. Front left (M113 pre-facelift)
30	A2204904219 BM BM90840H KLARIUS 323014	Catalytic converter. Front right (M113 pre-facelift)
50	A2204900121	Exhaust pipe. Rear left (M112)
60	A2204900221	Exhaust pipe. Rear right (M112)
50	A2204901021	Exhaust pipe. Rear left (M113)
60	A2204900821	Exhaust pipe. Rear right (M113)

Flanges

Part	Part no.	Description
220 / 245	A2024920281 (13 EUR)	Sealing ring. Sealing ring. Catalyst to tight fit / Left exhaust pipe to right exhaust pipe
220 / 245	Fa1 142951 (3 EUR)	Sealing exhaust pipe. Height: 19mm, Inner diameter: 51mm, Outer diameter: 64mm
200	A1264920845 (12 EUR)	Flange. Catalyst to rear exhaust pipe
200	HJS 82007055 (35 EUR)	Split flange. For pipe diameter of 55mm. Distance between holes: 78mm
200	HJS 82007060 (35 EUR)	Split flange. For pipe diameter of 60mm. Distance between holes: 85mm
210	A1269970041 (6 EUR)	Sealing ring. Catalyst on flange
210	Fa1 141955 (2 EUR)	Exhaust pipe gasket. Height 15mm, Inner diameter 55.6mm, Outer diameter 64.5mm

Replacing rusted flanges with split flanges

The OE cast iron flanges corrode and eventually split causing exhaust leaks. These are constructed of cast iron (despite being fitted to a stainless steel exhaust) and inevitably deteriorate and split. These parts are integral to the exhaust and are not available separately. The only option until now has been to buy a new exhaust at vast expense. Or to buy new flanges, cut them up, fit and re-weld them - a tricky job. None of these are an ideal solution to this common fault.

On M112 and M113 exhausts there are 3 factory mounted flange connections: two in the front (middle of the car) and one in the rear. Once they get rusted, the only option is to cut them off and install split flanges instead.

Required parts:

Sealing ring (A2024920281) x2
Graphite sealing ring (A1269970041)
Split flange for pipe diameter of 60mm (HJS 82007060) x2
Split flange for pipe diamater of 55mm (HJS 82007055)

The diameter of M112 and M113 exhaust pipes is 55mm except for the rear pipe of the right front flange connection, which has 60mm diamater (55mm pipe slips into the 60mm pipe).

Even though most of the pipes are 55mm, since the diameter of 55mm pipes increases closer to the connection, it might be required to install 60mm split flange instead (at least on one side of the connection) or use longer bolts (not included in split flange set).

The principle of applying split flanges on the front flange W220 exhaust connections is very similar as on BMW E46 exhaust:

BMW E46 M3 Flanges Repair Kit

Exhaust transmission mount

The arms of the exhaust transmission mount are of a different shape for 5-speed vs 7-speed transmission vehicles. Diesel engine on S320 has only one (right) arm.

Part	Part no.	Description
90	A2204922241 (17 EUR)	Bracket. Catalyst to transmission left (Code: 427 - AUTOMATIC TRANSMISSION 7-SPEED)
100	A2204922341 (30 EUR)	Bracket. Catalyst to transmission right (Code: 427 - AUTOMATIC TRANSMISSION 7-SPEED)
90	A2204920141 (58 EUR)	Bracket. Catalyst to transmission left
100	A2204920241 (30 EUR)	Bracket. Catalyst to transmission right
100	A2204921141	Bracket. Catalyst to transmission right (OM613/S320)
110	A1404920018 (6 EUR)	Base plate. Bracket to transmission
120	A1404920118 (6 EUR)	Base plate. Bracket to transmission
140	N910105008014 (2 EUR)	Hexagon head bolt. Bracket to transmission M8x35. x2
150	A1294900044 (7 EUR)	Plate. Exhaust pipe suspension to transmission
160	A1409900750 (2 EUR)	Collar nut f shaft. Exhaust pipe suspension to transmission M8. x4

Rusted off transmission mounts

Dimensions of the original U-profile

Distance between hole centres: 4cm

Making aftermarket U-profiles

Materials needed:

U-profile made of steel S235, dimensions: 35x35x2mm (two pieces cut in length of 7.5cm).
Bolt M8x16, nut M8, washer M8 wide (four pieces)

Bracket

Part	Part no.	Description
170	A2204921641 (8 EUR)	Bracket. Top front
180	A2204921741 (14 EUR)	Bracket. Bottom front
190	N910143008019 (3 EUR)	Hexalobular bolt. At bracket M8x60

Exhaust manifold

Exhaust manifold for 6-cylinder (M112) vehicles:

Exhaust manifold for 8-cylinder (M113) vehicles:

Screening plates

Exhaust system screening plates for 6-cylinder (M112) vehicles:

Exhaust system screening plates for 8-cylinder (M113) vehicles:

Issues

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 below provides 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.
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.

DIY Procedures

Diagnose Blocked Catalytic converter

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.