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Pelican Technical Article:

Intake Manifold Removal

Steve Vernon

Time:

6 hours6 hrs

Tab:

$20 to $270

Talent:

****

Tools:

10mm socket, 15mm, (2) 17mm wrenches, 6mm, 5mm, 4mm Allen, pliers, flathead screwdriver, oil filter wrench, rags

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

New O-rings, white lithium grease, intake manifold gaskets

Hot Tip:

Don't let anything fall into the engine openings

Performance Gain:

Proper running engine

Complementary Modification:

Replace worn out hoses

The intake manifold will need to come off the engine for a multitude of reasons including replacing the head gasket. While it is not a terribly difficult job it is time consuming. If you have never pulled an intake manifold before make sure to give yourself at least the full six hours to perform the work. Also make sure to bag up all hardware you remove in plastic baggies and clearly label each one.

You're going to be working on the fuel system so have a fire extinguisher handy (and know how to use it). there will be some spillage of fuel as it's nearly impossible to prevent while working on the injectors and fuel rail. Also, wear chemical resistant gloves if you don't want to get any gasoline on your hands, and make sure that you have plenty of paper towels or rags to help you clean up. Perform the work in a clear, open, and well-ventilated space. It may not hurt to have an assistant around in case there are any problems.

You will need to remove the cross over air pipe before beginning. It will make the job easier if you also remove the resonance valve and throttle body. Please see our articles on air cross over pipe, throttle body removal and resonance valve removal for further assistance.

Before you open the fuel system up it is a good idea to relieve the pressure in the system.
Figure 1

Before you open the fuel system up it is a good idea to relieve the pressure in the system. The best way to do this is to remove the fuel pump relay and crank the engine over a few times. This will draw the fuel already in the system out and relieve some of the pressure. The fuel pump relay is located in the upper right side of the engine bay behind the battery. There is a plastic tray behind the battery that you can move out of the way (red arrow).

If your hands are small enough you can reach down in the area between the hood and cowl and remove the fuel pump relay (red arrow).
Figure 2

If your hands are small enough you can reach down in the area between the hood and cowl and remove the fuel pump relay (red arrow). The relay sits tightly in the mount so wiggling it out helps. If your hands are too big you will need to remove the battery first to get at it from the front; of course this means you will need to disconnect the battery to remove it then reconnect it to crank the motor with the relay removed. Please see our article on battery removal for further assistance. With the relay removed crank the ignition on. The car will turn over and then die. Do this about 2-3 times. It will help drain excess fuel out of your system. Also, open the gas cap to help depressurize the system. Then, make sure that the car has cooled down. You don't want to be working with gasoline when the car is hot.

Lift the plastic cover off the wiring harness (red arrow) to expose the fuel rail below (yellow arrow).
Figure 3

Lift the plastic cover off the wiring harness (red arrow) to expose the fuel rail below (yellow arrow).

Open the cap on the Schrader valve (red arrow).
Figure 4

Open the cap on the Schrader valve (red arrow). Use a small flathead screwdriver and gently press the release valve. It is a good idea to have a rag wrapped around the valve to catch any fuel that escapes.

Cut the zip ties on the wiring harness to give you room to move them (red arrows).
Figure 5

Cut the zip ties on the wiring harness to give you room to move them (red arrows). Use care not to cut any of the electrical lines.

You are going to be opening holes that go into the engine.
Figure 6

You are going to be opening holes that go into the engine. Before you begin get a can of compressed air and blow all the dust and debris away from the injector ports (red arrows).

Use a10mm socket or wrench and remove the single bolt (red arrow) holding the wiring tray in place.
Figure 7

Use a10mm socket or wrench and remove the single bolt (red arrow) holding the wiring tray in place.

With everything loose move the tray and disconnect the wiring from the injectors (red arrows, two shown).
Figure 8

With everything loose move the tray and disconnect the wiring from the injectors (red arrows, two shown). Squeeze the wire clips together and pull the connectors straight off.

Disconnect the vacuum line from the fuel pressure regulator (red arrow).
Figure 9

Disconnect the vacuum line from the fuel pressure regulator (red arrow).

Move the wiring and tray out of the way towards the top of the engine (red arrow).
Figure 10

Move the wiring and tray out of the way towards the top of the engine (red arrow). Remove the dip stick (yellow arrow).

You will need to remove the oil filter lid to get access to the two rear 5mm Allen bolts on the injector rail.
Figure 11

You will need to remove the oil filter lid to get access to the two rear 5mm Allen bolts on the injector rail. Use an oil filter socket or wrench and remove the lid (red arrow). Please see our article on oil and filter changing if you need additional help or would like to change the filter while you are doing this job.

There are two fuel lines attached to the rail.
Figure 12

There are two fuel lines attached to the rail. Use a 15mm and 17mm wrench to break the first line free and then two 17mm wrenches to break the other line (red arrows). Always support the fitting with another wrench when separating fuel lines.

There are five 5mm Allen bolts holding the fuel rail to the intake manifold and engine (red arrows).
Figure 13

There are five 5mm Allen bolts holding the fuel rail to the intake manifold and engine (red arrows).

Some of the Allen bolts at the front and rear of the fuel rail are difficult to reach (red arrows for example).
Figure 14

Some of the Allen bolts at the front and rear of the fuel rail are difficult to reach (red arrows for example). Always make sure the Allen is well seated in the bolt head before attempting to remove. You do not want to strip these bolts out. If you think they are difficult to remove with a regular Allen try removing them with an Easy Out.

Pull the injectors and fuel rail straight back on the angle of the injectors and out from the head (red arrow).
Figure 15

Pull the injectors and fuel rail straight back on the angle of the injectors and out from the head (red arrow). They are just held in by the O-rings. You will feel a "pop" when they let go.

Take the injectors in the rail to your work bench.
Figure 16

Take the injectors in the rail to your work bench. Be sure to put a few rags in the open holes in the manifold to prevent anything from falling into the engine (red arrows). If you drop something into these holes you must get it out. These holes go directly into the cylinder head. Any piece of dirt, debris or anything dropped inside the cylinder head will cause catastrophic damage if left in!

Remove the 4mm Allen holding the dip stick tube to the bracket and then pull the tube up and out of the motor (red arrow).
Figure 17

Remove the 4mm Allen holding the dip stick tube to the bracket and then pull the tube up and out of the motor (red arrow).

Use a 6mm Allen and remove the three Allen bolts holding the manifold to the head.
Figure 18

Use a 6mm Allen and remove the three Allen bolts holding the manifold to the head. Be sure to remove the dipstick tube bracket after removing the Allen bolt (red arrow).

There are two tubes connecting the lower manifold to the upper manifold.
Figure 19

There are two tubes connecting the lower manifold to the upper manifold. Use a Philips head screwdriver and remove the four metal clamps (red arrow, two shown).

Reach in between the manifold and water pump and remove the two vacuum hoses attached to the lower section of the manifold between the number two and three intake runners (red arrow).
Figure 20

Reach in between the manifold and water pump and remove the two vacuum hoses attached to the lower section of the manifold between the number two and three intake runners (red arrow). These will probably be very brittle and break when removing; be prepared and order these hoses in advance.

Detach the small vacuum line from the top of the number three intake runner (red arrow).
Figure 21

Detach the small vacuum line from the top of the number three intake runner (red arrow).

Separate the wiring connection for the knock sensor below the number four intake runner (red arrow).
Figure 22

Separate the wiring connection for the knock sensor below the number four intake runner (red arrow).

Wiggle, lift and pull the intake manifold from the head (red arrow) and the two openings on the lower intake manifold (yellow arrow, one shown).
Figure 23

Wiggle, lift and pull the intake manifold from the head (red arrow) and the two openings on the lower intake manifold (yellow arrow, one shown).

Make sure to stuff clean rags into the opening on the head (red arrows), the throttle body (yellow arrow) and the lower manifold (green arrows).
Figure 24

Make sure to stuff clean rags into the opening on the head (red arrows), the throttle body (yellow arrow) and the lower manifold (green arrows).

Inspect all the gaskets, hoses and lines for damage or excessive wear and replace as needed.
Figure 25

Inspect all the gaskets, hoses and lines for damage or excessive wear and replace as needed. You must always replace the intake manifold gaskets (red arrows). It is always a good idea and cheap insurance to replace the vacuum hoses (green arrow) and rubber boots or tubes that connect the manifolds (yellow arrows). Installation is the reverse of removal. Now would be a really good time to replace any suspect vacuum lines.

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