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Intake and Exhaust Gasket Replacement
 
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Pelican Technical Article:

Intake and Exhaust Gasket Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$8 to $20

Talent:

**

Tools:

17mm socket, 13mm, 12mm wrench

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Gasket

Hot Tip:

Soak the hardware with penetrating oil before beginning

Performance Gain:

No exhaust or intake leaks

Complementary Modification:

Overhaul turbo

The exhaust and intake manifold gasket on the W123 is a single piece and can only be replaced by removing both the exhaust and intake manifolds. The gaskets do last an extremely long time but once you remove the intake or exhaust manifolds you must replace the gasket. You will need to remove several components to get access to the manifolds and if you have a later model turbo diesel, that includes removing the trap oxidizer as well. For the sake of this article the intake and exhaust gasket was removed from a 1985 300TD, your system may vary.

Obviously the exhaust and plumbing system gets extremely hot so make sure that you are working on a cold engine before you begin to work on the manifolds.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts having been replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please leave your vehicle information.

You will need to remove the turbo first, so please see our article on turbo removal for additional instruction.
Figure 1

You will need to remove the turbo first, so please see our article on turbo removal for additional instruction.

If your vehicle is equipped with a trap oxidizer (red arrow) you will need to remove this; again, please see our article on trap oxidizer removal for further assistance.
Figure 2

If your vehicle is equipped with a trap oxidizer (red arrow) you will need to remove this; again, please see our article on trap oxidizer removal for further assistance. If your vehicle still has the EGR valve you will need to disconnect it from the intake manifold (yellow arrow).

Remove the wiring connection for the turbo boost sensor on the rear of the intake manifold by pulling it up.
Figure 3

Remove the wiring connection for the turbo boost sensor on the rear of the intake manifold by pulling it up.

Use a 13mm wrench and remove the bolt holding the transmission tube to the rear of the intake manifold (red arrow).
Figure 4

Use a 13mm wrench and remove the bolt holding the transmission tube to the rear of the intake manifold (red arrow).

Move the tube out of the way and use a 12mm wrench to remove the turbo boost line from the rear of the manifold.
Figure 5

Move the tube out of the way and use a 12mm wrench to remove the turbo boost line from the rear of the manifold.

Use a 17mm socket and remove the seven nuts and washers holding the manifolds in place.
Figure 6

Use a 17mm socket and remove the seven nuts and washers holding the manifolds in place.

You will need to pull the intake manifold (red arrow) forward first but on some models it will not clear the exhaust manifold (yellow arrow) so reach down and wiggle the exhaust manifold forward until the intake will clear.
Figure 7

You will need to pull the intake manifold (red arrow) forward first but on some models it will not clear the exhaust manifold (yellow arrow) so reach down and wiggle the exhaust manifold forward until the intake will clear.

Remove the intake manifold and check to see if there is oil in the manifold; any pools of oil which are excessive is the sign of a sick motor.
Figure 8

Remove the intake manifold and check to see if there is oil in the manifold; any pools of oil which are excessive is the sign of a sick motor.

With the intake manifold off you can remove the exhaust manifold.
Figure 9

With the intake manifold off you can remove the exhaust manifold.

Remove the old gasket as a single piece.
Figure 10

Remove the old gasket as a single piece.

Clean any old gasket material from around the ports and blocks; hopefully your engine is in better shape than our 300K miles project car.
Figure 11

Clean any old gasket material from around the ports and blocks; hopefully your engine is in better shape than our 300K miles project car. Installation is the reverse of removal.

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