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Pelican Technical Article:

Air Pump Removal

Kerry Jonsson

Time:

2 hours2 hrs

Tab:

$250

Talent:

**

Tools:

6mm Allen head socket, 13mm socket with ratchet or wrench, pliers

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

Air Pump

Hot Tip:

Remove the hose clamp first then loosen the air pump from the engine

Performance Gain:

Pass an emissions smog test

In the early years of the 500SL they used a CIS (Continuous Injection System) to inject fuel into the engine. This half mechanical system could continue to work even if the engine electronics completely failed. This type of fuel injection is more fuel efficient than a carburetor but not as precise as electronically controlled port fuel injection. To help pass emissions tests a belt driven air pump would be activated and fresh air would get pumped into the exhaust before the catalytic converter to help clean up harmful emissions. Mercedes Benz used an air pump driven by a clutch so they could turn the air pump on and off when conditions called for it. A seized air pump could throw you accessory drive belt off and then you would lose all accessories like your water pump and alternator. In this tech article we will go over all the steps to remove your air pump so you can replace it.

In order to remove your air pump you need to lift and support the front axle of your vehicle, remove the lower splash shield and the accessory drive belt. See our tech articles on jacking up and supporting your vehicle, lower splash shield removal and accessory driver belt removal.

ThisPicture illustrates underneath the engine on the right side by the air pump.
Figure 1

ThisPicture illustrates underneath the engine on the right side by the air pump. Start by removing the hose clamp (green arrow) at the back of the air pump. Squeeze the clamp and at the same time pull the hose off of the air pump.

ThisPicture illustrates the front of the air pump looking at it from underneath the car.
Figure 2

ThisPicture illustrates the front of the air pump looking at it from underneath the car. Remove the 6mm Allen head fastener (green arrow) that mounts the bottom of the air pump.

ThisPicture illustrates the front of the air pump looking at it from above.
Figure 3

ThisPicture illustrates the front of the air pump looking at it from above. Remove the 13mm fastener (green arrow) that mounts the top of the air pump. You do not have to remove the alternator or cooling fan to remove the air pump but it does give you much more room to work. See our technical articles on alternator removal and cooling fan removal. We have removed these items for photographic purposes. At this point you can pull the air pump out of the mounting brackets. Rest it on something or hang it using stiff wire, because the wiring harness for the clutch is still attached.

Follow the harness until you come to the first holder on the right side front frame in the engine compartment and remove it from the frame rail.
Figure 4

Follow the harness until you come to the first holder on the right side front frame in the engine compartment and remove it from the frame rail.

ThisPicture illustrates the right side inner fender in front of the strut mount.
Figure 5

ThisPicture illustrates the right side inner fender in front of the strut mount. Locate the air pump clutch electrical connector (green arrow) and slide it upwards to release it from its holder.

With the connector exposed squeeze the two locking tabs (green arrows) and pull the connector apart in the direction of the blue arrows.
Figure 6

With the connector exposed squeeze the two locking tabs (green arrows) and pull the connector apart in the direction of the blue arrows. You can now fully remove the air pump from the engine compartment. Installation is the reverse of the removal steps. Position the air pump in its brackets and tighten down the upper and lower mounting fasteners. Install the hose on the output flange and position the clamp to seal the hose. Install the accessory drive belt and any other components you may have removed to get better access to the air pump. Start the car and after a few minutes of running you should hear the air pump come on for a few minutes and then go off.

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Comments and Suggestions:
Aussie Comments: Hello I have a 1992 SL500. Just under the alternator there is a pump or something that has connection for looks a 3/8 pipe fitting. Mine is just open can you tell me what is suppose to go on it??. Thanks Austin
May 19, 2016
  Followup from the Pelican Staff: Can you share a photo of the part? Close up and a little further back to see the surrounding area? - Nick at Pelican Parts  

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