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Pelican Technical Article:

Trap Oxidizer Removal

Steve Vernon

Time:

3 hours3 hrs

Tab:

$0

Talent:

**

Tools:

17mm, 13mm (2) socket, 10mm wrench, flathead screwdriver

Applicable Models:

Mercedes-Benz 300TD (1979-85)

Parts Required:

Gasket

Hot Tip:

Soak the hardware with penetrating oil before beginning

Performance Gain:

Better performance

Complementary Modification:

Change air filter

The trap oxidizer was introduced by Mercedes for the California models, in some 1984 models, and was included in all models by the end of 1985. The trap does just that, it traps soot from the engine from being expelled out through the exhaust pipe. While this is a fine idea, Mercedes ended up having several problem with the trap and issued a recall. Over time the trap will become plugged up with soot and if it gets really bad, the internals of the trap can break down and enter the turbo blades causing damage. Even a partially blocked trap will end up with reduced performance and gas mileage.

While there are companies that make trap by-pass pipes, tampering with SMOG or emission equipment can be illegal in some states so make sure to check with your regulations before removing or tampering with any emission equipment.

The trap is attached to the exhaust so one of the tricks is to hit all of the hardware with a good penetrating oil a week before you plan on removing everything and repeating this a few times so the hardware can go through several heat cycles.

Obviously the turbo and plumbing system gets extremely hot so make sure that you are working on a cold engine before you begin to work on the turbo.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please leave your vehicle information.

On the later model turbo diesels Mercedes moved the air filter housing to make room for the trap oxidizer that sits below the turbo on some early California models and all later 1985 models (red arrow).
Figure 1

On the later model turbo diesels Mercedes moved the air filter housing to make room for the trap oxidizer that sits below the turbo on some early California models and all later 1985 models (red arrow). You do not need to remove the air filter housing on the later models but you will need to on the early ones. You will need to remove the turbo to remove the trap oxidizer so please see our article on turbo removal for additional assistance.

With the turbo removed you can see how the trap is attached to the exhaust manifold (red arrow) and supplies the gases to the turbo (yellow arrow).
Figure 2

With the turbo removed you can see how the trap is attached to the exhaust manifold (red arrow) and supplies the gases to the turbo (yellow arrow).

The exhaust manifold to trap bolts are hard to access while the turbo is in place so if you haven't done it already now is a good time to hit them with some penetrating oil.
Figure 3

The exhaust manifold to trap bolts are hard to access while the turbo is in place so if you haven't done it already now is a good time to hit them with some penetrating oil.

There is a pipe from the lower section of the trap (red arrow) that feeds the EGR valve (yellow arrow).
Figure 4

There is a pipe from the lower section of the trap (red arrow) that feeds the EGR valve (yellow arrow). We have removed the EGR valve for another job you do NOT need to remove it. Use a 10mm wrench and remove the clamp on the lower pipe and separate the pipe form the trap.

Use a 17mm socket and remove the three bolts that hold the mounts to the trap and engine block; two are shown (red arrows) and one is down below.
Figure 5

Use a 17mm socket and remove the three bolts that hold the mounts to the trap and engine block; two are shown (red arrows) and one is down below.

Use your two 13mm wrenches or sockets and remove the two nuts and bolts holding the trap to the lower mount (red arrow).
Figure 6

Use your two 13mm wrenches or sockets and remove the two nuts and bolts holding the trap to the lower mount (red arrow).

There are three 13mm nuts and bolts holding the trap to the exhaust manifold, you can remove two from the top but the bottom one has a brace that mounts to the starter housing and needs to be removed from below (red arrow).
Figure 7

There are three 13mm nuts and bolts holding the trap to the exhaust manifold, you can remove two from the top but the bottom one has a brace that mounts to the starter housing and needs to be removed from below (red arrow).

With the exhaust manifold free you can remove the trap from the vehicle, use care as it is surprisingly heavy.
Figure 8

With the exhaust manifold free you can remove the trap from the vehicle, use care as it is surprisingly heavy. When reinstalling make sure to replace the gaskets.

There are aftermarket kits that eliminate the trap and attach directly to the out port of the exhaust manifold (red arrow) and to the turbo but check with the regulations in your area before making this modification.
Figure 9

There are aftermarket kits that eliminate the trap and attach directly to the out port of the exhaust manifold (red arrow) and to the turbo but check with the regulations in your area before making this modification. You will also need to get the EGR block off plate if you go this route. Installation is the reverse of removal.

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