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Fixing Your Mercedes Air Pump Check Valves
 
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Pelican Technical Article:

Fixing Your Mercedes Air Pump Check Valves

Steve Vernon

Time:

1 hour1 hr

Tab:

$480

Talent:

**

Tools:

E12 Torx driver and extension

Applicable Models:

Mercedes-Benz ML320 (1998-03)
Mercedes-Benz W203 (2001-07)

Parts Required:

New air pump

Hot Tip:

Use care working on old rubber hoses

Performance Gain:

Pass a smog test

Complementary Modification:

New Air Pump hoses

If your car is not passing a smog test one of the things that could be wrong is the air pump check valves. This article will show you how to replace the air pump check valves on a Mercedes-Benz W203.

Begin by disconnecting the ground from the battery and making sure it can not accidentally make contact again while you are working.

You will need to remove the two air inlet ducts as well as the front engine cover to get access to the air filter housing on top of the engine.

Remove each duct by compressing them towards the engine and slipping them off the air inlet.

With the ducts off remove the front engine cover. It pulls up and away from the engine. The cover is held on by five clips and will easily come off with hand pressure.

Next you will need to remove the main engine cover that also houses the air filters. It is held on by four pressure clips. You can see the two at the front of the engine, to remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well.

Now you have access to the air pump check valves. The valves sit right at the front of the engine on both sides of the air pump.

There is a hose that runs between the two check valves that connects to the air pump, as well as a smaller vacuum line between the two units. Remove both of these lines, inspect them for age and cracks and replace them as needed.

There is a single E12 Torq bolt holding the check valve to the manifold remove it and wiggle the valve from the manifold. Use caution when removing them as there is a metal extension that goes down into the manifold and it can get stuck with age.

Installation is the reverse of removal.

Begin by disconnecting the ground from the battery and making sure it can not accidentally make contact again while you are working.
Figure 1

Begin by disconnecting the ground from the battery and making sure it can not accidentally make contact again while you are working.

You will need to remove the two air inlet ducts (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.
Figure 2

You will need to remove the two air inlet ducts (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.
Figure 3

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.

With the ducts off remove the front engine cover.
Figure 4

With the ducts off remove the front engine cover. It pulls up and away from the engine (yellow arrow).

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.
Figure 5

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.

Next you will need to remove the main engine cover that also houses the air filters.
Figure 6

Next you will need to remove the main engine cover that also houses the air filters. It is held on by four pressure clips. You can see the two at the front of the engine (red arrows).

To remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well (red arrows).
Figure 7

To remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well (red arrows).

Now you have access to the air pump check valves (yellow arrows).
Figure 8

Now you have access to the air pump check valves (yellow arrows). The valves sit right at the front of the engine above the coolant pump and on both sides of the air pump (red arrow).

There is a hose that runs between the two check valves that connects to the air pump (red arrows), as well as a smaller vacuum line between the two units (yellow arrows).
Figure 9

There is a hose that runs between the two check valves that connects to the air pump (red arrows), as well as a smaller vacuum line between the two units (yellow arrows). Remove both of these lines, inspect them for age and cracks and replace them as needed.

There is a single E12 Torq bolt (red arrow) holding the check valve to the manifold remove it and wiggle the valve from the manifold.
Figure 10

There is a single E12 Torq bolt (red arrow) holding the check valve to the manifold remove it and wiggle the valve from the manifold. Use caution when removing them as there is a metal extension that goes down into the manifold and it can get stuck with age.

Use caution when removing them as there is a metal extension that goes down into the manifold (red arrow) and it can get stuck with age.
Figure 11

Use caution when removing them as there is a metal extension that goes down into the manifold (red arrow) and it can get stuck with age.

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Comments and Suggestions:
Bharat Bhatia Comments: How can I make sure that the air pump valves are the problem? How much are these parts?
May 22, 2015
  Followup from the Pelican Staff: Check if the valve block air when no vacuum is present, and allow air to flow when vacuum is present. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 

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