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6-Cylinder Intake Manifold Replacement
 
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Pelican Technical Article:

6-Cylinder Intake Manifold Replacement

Nick Czerula

Time:

4 hours4 hrs

Tab:

$150

Talent:

*****

Tools:

Flathead screwdriver, T25, T30 Torx, E10, E12 Inverted Torx, 8mm socket, 17mm, 22mm, 24mm, wrenches

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Intake manifold gaskets, EGR air pipes

Hot Tip:

Work with a cool engine

Performance Gain:

Seal vacuum leaks, repair faulty gaskets

Complementary Modification:

Replace fuel injector O-rings

In its simplest terms an engine is a self-powered air pump. An air pump draws in air, compresses it and then expels the compressed air. Your engine does much the same thing. It draws in air through your intake manifold. The intake manifold is one of the parts of your engine that contributes to the power output. Make the ports too small and airflow travels at high speed at low rpm but is restricted at high rpm. If your intake manifold volume is too large then airflow will be slow at low rpm (low mid-range power and throttle response) but will make more horsepower at higher rpm. This is why modern intake manifolds have some sort of intake runner control to get the best of both worlds. In this tech article we are going to go over all of the steps to remove the intake manifold for the six and eight cylinder engines.

W211 models with 6-cylinder engines utilize flat gaskets for the intake manifold. Over time the gaskets fail and leaks develop. If you have a hard to find vacuum leak, replace your intake manifold gaskets. If you find oil inside your intake manifold, reseal the crankcase breather covers. Clean the inside of the intake manifold thoroughly and be careful not to get any debris inside the cylinder head during the procedure. Removing the intake manifold will also give you easy access to the knock sensors.

When preparing to remove your intake manifold, be sure to have all the correct parts on hand and leave enough time in the day. I suggest plan for one-half a day. The EGR pipe at the rear of the intake can be a pain. Nine out of ten times when removing the intake manifold this pipe breaks, so be sure to have one on hand.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Disconnect the battery. See our tech article on battery replacing.

Working at the engine cover (red arrow).
Figure 1

Working at the engine cover (red arrow). Pull off the two front sir duct hoses (green arrows).

To detach the ducts, pull them straight off the engine cover / air filter housing.
Figure 2

To detach the ducts, pull them straight off the engine cover / air filter housing. Then pull the front of the duct out of the radiator support and remove it from the engine. Repeat this step for each duct.

Lift up and remove the front engine cover.
Figure 3

Lift up and remove the front engine cover.

Then, pull the engine cover / air filter housing straight up to remove it.
Figure 4

Then, pull the engine cover / air filter housing straight up to remove it. The cover is held on by four metal clips that grab onto rubber mounts, with the front two shown (red arrows). The rear of the cover has two as well. Once detached, remove the engine cover / air filter housing from the engine. Remove the mass airflow sensor. See our tech article on mass airflow sensor removing.

Working at the rear of the intake manifold, pull the breather hose (red arrows) straight off the duct to remove it.
Figure 5

Working at the rear of the intake manifold, pull the breather hose (red arrows) straight off the duct to remove it.

Working at the right side valve cover, pull the breather hose straight off the breather cover to remove it.
Figure 6

Working at the right side valve cover, pull the breather hose straight off the breather cover to remove it.

Working at the rear of the intake manifold, pull the breather hose junction out of the intake manifold.
Figure 7

Working at the rear of the intake manifold, pull the breather hose junction out of the intake manifold. Pull it straight up to remove it. Once up, pull the hard line (red arrow) out of the breather hose and lay it aside.

Unclip the duct-retaining tab (green arrow).
Figure 8

Unclip the duct-retaining tab (green arrow). Then pull the duct off the throttle housing in the direction of the red arrow and remove it from the engine.

Working below the throttle housing, detach the wiring harness from the clip at the bottom of the throttle housing.
Figure 9

Working below the throttle housing, detach the wiring harness from the clip at the bottom of the throttle housing. Then disconnect the electrical connector by squeezing the release tabs (green arrow) and pulling the connector straight off.

Working at the right side valve cover, disconnect the ignition coil electrical connectors by pressing the release tab and pulling them straight out (red arrows).
Figure 10

Working at the right side valve cover, disconnect the ignition coil electrical connectors by pressing the release tab and pulling them straight out (red arrows). Then cut the zip tie (green arrow) securing the wiring harness to the coil.

Working at the right side valve cover, disconnect the fuel injector electrical connectors by squeezing the release tabs and pulling them straight off (red arrows).
Figure 11

Working at the right side valve cover, disconnect the fuel injector electrical connectors by squeezing the release tabs and pulling them straight off (red arrows). Then disconnect the electrical connector at the EGR system (green arrow). Once all the connectors have been disconnected, press the plastic tab (yellow arrow) toward the right side fender and lift the wiring harness housing up off the fuel rail.

Back at the right side of the engine, remove the fuel pressure test port cap (red arrow).
Figure 12

Back at the right side of the engine, remove the fuel pressure test port cap (red arrow). Then cover the port with a rag and press the Schrader valve down to relieve fuel pressure. Reinstall the cap once the pressure is relieved.

Working at the left side of the engine, use a 17mm line wrench and remove the fuel line at the fuel rail.
Figure 13

Working at the left side of the engine, use a 17mm line wrench and remove the fuel line at the fuel rail. Once removed, cover the line and fitting on the fuel rail with a rag to collect any excess fuel.

Working at the rear of the intake manifold, remove the EGR tube (green arrow).
Figure 14

Working at the rear of the intake manifold, remove the EGR tube (green arrow). Here's the tricky part. The nut for the tube is usually stuck. If it is not, loosen the 24mm nut on the pipe at the EGR side. Once loose, the intake will come off. If it is stuck, you are better off removing the fuel injectors first to allow better access to the fitting on the EGR manifold. Start by removing the fuel injectors. See our tech article on fuel injectors removing. Then remove the two E10 inverted Torx fasteners (red arrows). Removing these allows the tube to rotate slightly, preventing distorting the pipe.

Then, counterhold the 22mm fitting (red arrow) while loosening the 24mm tube nut (green arrow).
Figure 15

Then, counterhold the 22mm fitting (red arrow) while loosening the 24mm tube nut (green arrow). Once loose, remove the tube from the engine.

Next, remove the vacuum hose right below the tube.
Figure 16

Next, remove the vacuum hose right below the tube. The tube is left in place to help locate the vacuum hose on the intake manifold.

Working at the front of the intake manifold, remove the secondary air pipe by pulling it off the valves and pump (red arrows).
Figure 17

Working at the front of the intake manifold, remove the secondary air pipe by pulling it off the valves and pump (red arrows).

Next, remove the vacuum hoses at the left side secondary air valve and the solenoid (red arrows).
Figure 18

Next, remove the vacuum hoses at the left side secondary air valve and the solenoid (red arrows).

Move to the center of the intake manifold.
Figure 19

Move to the center of the intake manifold. Remove the two vacuum hoses (red arrows).

Now remove the vacuum hose from the right side secondary air valve (green arrow).
Figure 20

Now remove the vacuum hose from the right side secondary air valve (green arrow).

Working at the left rear of the intake manifold, remove the vacuum hose (red arrow).
Figure 21

Working at the left rear of the intake manifold, remove the vacuum hose (red arrow).

Remove the eight E12 inverted Torx intake manifold fasteners (red arrows).
Figure 22

Remove the eight E12 inverted Torx intake manifold fasteners (red arrows). The right side shows this with the fuel injectors removed. The left side is similar.

With help from a friend, lift the intake manifold up to remove it, untangling wires and hoses as you lift it.
Figure 23

With help from a friend, lift the intake manifold up to remove it, untangling wires and hoses as you lift it. You will need to rotate it to the right and then feed the secondary air valve out from under the harness housing at the front. Once removed, plug the intake ports to prevent debris from falling in. Vacuum out any debris surrounding the area and clean the gasket sealing surfaces.

With the intake manifold removed you can now replace the intake manifold gaskets.
Figure 24

With the intake manifold removed you can now replace the intake manifold gaskets. Be sure to clean the sealing surface before installing new ones. If you had a hard time with the EGR tube, be sure the fitting (green arrow) is tight before trying to reinstall the tube. Once you make repairs and install new gaskets, tighten the intake manifold fasteners to 20 Nm. Reassemble the intake components in the reverse order of removal. Be sure all hoses and electrical connectors are routed as they were when removed.

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