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Pelican Technical Article:

Intake Manifold Gasket Replacement

Kerry Jonsson

Time:

6 hours6 hrs

Tab:

$100

Talent:

****

Tools:

10mm socket with ratchet, 6mm Allen head socket, flat head screwdriver, 10mm wrench, pliers

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

Intake manifold gaskets

Hot Tip:

Replace all hoses connected to the intake manifold since they will probably break

Performance Gain:

Better engine performance.

An engine is an air pump. It draws in air as fuel is being injected into your intake manifold. As the piston drops down it causes a vacuum in the combustion chamber. With the intake valve open,  fuel and air are drawn into the combustion chamber preparing for ignition. One of the reasons fuel injection has taken over is the increase in fuel efficiency. Sensors monitor the air being taken in and the engine control unit decides how much fuel to add in very precise amounts. If an intake manifold were to allow unmeasured air into the engine the engine control unit will not inject the correct amount of fuel and the car will run lean. This can cause a surge and/or your check engine light to come on. In this tech article we will go over all the steps necessary to remove your intake manifold so you can change the gaskets.

You do not have to remove the fuel rail to take off the intake manifold but we have done so for photographic purposes. We do recommend you take off the fuel rail as it does make access to tight fasteners much easier. You also do not have to remove the throttle body and MAF sensor but we have done so for work on other articles on those subjects. See our tech articles on MAF and throttle body removal for further instructions.

This photo illustrates the front of the intake manifold.
Figure 1

This photo illustrates the front of the intake manifold. We have not removed the fuel rail yet. Unplug the coolant temperature sending unit by squeezing the connector and pulling straight upward.

Next unplug the coolant temperature switch.
Figure 2

Next unplug the coolant temperature switch. Our connector is broken but all you have to do is squeeze the connector and pull it straight up.

Unplug that the coolant temperature sensor by squeezing the connector and pulling straight up.
Figure 3

Unplug that the coolant temperature sensor by squeezing the connector and pulling straight up. If the connector is difficult to pull up you can use a pick to remove the metal snap ring before disconnecting connecter.

If you would like to remove the entire wiring harness from the intake manifold as we did, start by unplugging the variable valve timing connector (green arrow) on the left cylinder head.
Figure 4

If you would like to remove the entire wiring harness from the intake manifold as we did, start by unplugging the variable valve timing connector (green arrow) on the left cylinder head. Follow the next step for removing the entire harness.

Then, unplug the variable valve timing actuator connector (green arrow) on the right side cylinder head.
Figure 5

Then, unplug the variable valve timing actuator connector (green arrow) on the right side cylinder head. Then remove the electrical harness from the engine, noting the routing for reinstallation.

Looking down at the front of the intake manifold remove the two 6 mm Allen head fasteners (green arrows) that hold the intake manifold and spark plug wire plastic covers in place.
Figure 6

Looking down at the front of the intake manifold remove the two 6 mm Allen head fasteners (green arrows) that hold the intake manifold and spark plug wire plastic covers in place.

If you would like to remove the spark plug wire plastic cover entirely you can remove the 13 mm fastener (green arrow) and the 6mm Allen head fastener (yellow arrow) and move it out of the way.
Figure 7

If you would like to remove the spark plug wire plastic cover entirely you can remove the 13 mm fastener (green arrow) and the 6mm Allen head fastener (yellow arrow) and move it out of the way. We have opted to leave our ignition cover in place.

Remove the fifteen 6mm Allen head fasteners (green arrows).
Figure 8

Remove the fifteen 6mm Allen head fasteners (green arrows). Three fasteners are hidden (yellow arrows), one behind the vacuum line pipe and two behind the back of the intake manifold itself. These bolts will be tight and corroded in place. Make sure your Allen key is fully seated boldly in the bolt. You may want a hammer down on your socket a few times to break loose the corrosion. Don't be surprised if you snap the head of a bolt or two. You may have to drill them out.

Working at the back of the intake manifold on left side, loosen the hose clamp and remove the heater hose from the intake manifold.
Figure 9

Working at the back of the intake manifold on left side, loosen the hose clamp and remove the heater hose from the intake manifold.

Remove the metal vacuum pipe by removing the 10 mm mounting fastener (green arrow) and 15mm flare nut fitting (yellow arrow) with a wrench.
Figure 10

Remove the metal vacuum pipe by removing the 10 mm mounting fastener (green arrow) and 15mm flare nut fitting (yellow arrow) with a wrench.

This photo illustrates the front of the intake manifold by the sensors.
Figure 11

This photo illustrates the front of the intake manifold by the sensors. Loosen the hose clamp (green arrow). You will remove the hose as you lift the intake manifold up.

This photo illustrates the back of the intake manifold.
Figure 12

This photo illustrates the back of the intake manifold. Remove the three 10mm fasteners (green arrows) that mount the throttle linkage. Once the fasteners are removed, move the linkage aside to access the ball socket. Se next step for ball socket detaching.

You can use a flathead screwdriver to pop off the throttle linkage socket (green arrow).
Figure 13

You can use a flathead screwdriver to pop off the throttle linkage socket (green arrow). The intake should be disconnected now and ready for removal.

You should now be able to lift up on the intake manifold and separate it from the engine.
Figure 14

You should now be able to lift up on the intake manifold and separate it from the engine. Mercedes Benz uses a two piece manifold, one upper side, one lower side. These manifolds may start to separate when you lift up on the intake manifold. Installation is the reverse of the removal steps. Position the intake manifold gaskets on the cylinder head and install the intake manifold taking care to line up the front of the intake manifold pipe with the coolant hose that attaches to the bleeder screw housing. Torque the fasteners down in an alternating pattern crisscrossing from one side of the manifold to the other. Attach the throttle linkage bowl socket at the back of the intake manifold. Tighten down the three fasteners that hold the throttle linkage at the top of the intake manifold. Install the heater hoses at the left rear of the intake and tighten the hose clamp. Fit the spark plug wire plastic cover and tighten down the four fasteners that mount it. Pull back in all electrical connectors at the three sensors and two variable valve timing actuators. If you remove the fuel rail refit the fuel rail as per our tech article on fuel rail removal. Start the engine light warm up and make sure runs smooth. Check for coolant leaks

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