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Pelican Technical Article:

Exhaust Gasket Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$10 to $20

Talent:

**

Tools:

19mm, 17mm, 12mm wrench, 13mm, 12mm socket, extensions, universal joint, 5mm Allen

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

New gasket and nuts

Hot Tip:

Soak with penetrating oil before beginning work

Performance Gain:

Better-running engine, improved fuel mileage

Complementary Modification:

New O2 sensor

There are two exhaust manifolds on the M104 engine, one that services the number 1-3 cylinders and the other services the 4-6. You can replace the gaskets for either manifold separately but the number 1-3 cylinder manifold has a different gasket for the number 1 cylinder. You must replace all three gaskets once you remove each manifold.

Begin by presoaking the manifold nuts with good penetrating oil before you begin the job. Preferably, let them soak overnight. You will need to safely raise and support the vehicle and remove the air filter box, MAF, lower engine tray and air cross over pipe. Please see our article on safely jacking up and supporting the vehicle as well as removing the air filter, MAF, engine lower tray and cross over pipe for further assistance.

This photo illustrates the two separate manifolds for the M104 engine (red arrows).
Figure 1

This photo illustrates the two separate manifolds for the M104 engine (red arrows).

There are a few other systems that must be removed from the manifold before they can be removed from the engine; these include the EGR tube (red arrow), the air pump injection tube (yellow arrow) along with the manifold retaining nuts (green arrow).
Figure 2

There are a few other systems that must be removed from the manifold before they can be removed from the engine; these include the EGR tube (red arrow), the air pump injection tube (yellow arrow) along with the manifold retaining nuts (green arrow).

Use a 5mm Allen and remove the bolt holding the air pump tube to the head (red arrow).
Figure 3

Use a 5mm Allen and remove the bolt holding the air pump tube to the head (red arrow).

Use a 12mm socket and remove the nuts you can get easy access to.
Figure 4

Use a 12mm socket and remove the nuts you can get easy access to. When removing the nuts some will come off the studs (red arrows). Sometimes the studs will back out with the nuts (yellow arrow).

Working under the car, remove the 13mm nut holding the air pump tube and valve to the engine block (green arrow).
Figure 5

Working under the car, remove the 13mm nut holding the air pump tube and valve to the engine block (green arrow). While you can separate the tube from the valve (red arrow) it is easier to separate the unit from the air pump where the tube attaches to the pump (yellow arrow).

Using a 13mm socket with a series of extensions, remove the two bolts holding the exhaust pipes to the front manifold (red arrows) and rear manifold (yellow arrows).
Figure 6

Using a 13mm socket with a series of extensions, remove the two bolts holding the exhaust pipes to the front manifold (red arrows) and rear manifold (yellow arrows). Remove the rest of the lower nuts from the manifold to block. You can now pull the front manifold off from above.

The front manifold has three separate gaskets.
Figure 7

The front manifold has three separate gaskets. The rear two (red arrows) are common but the number one cylinder is different to fit around the head design (yellow arrow).

Remove the upper retaining nuts (red arrow) on the rear manifold.
Figure 8

Remove the upper retaining nuts (red arrow) on the rear manifold.

Separate the EGR tube from the manifold by supporting the lower manifold nut with a 17mm wrench and using a'mm wrench to loosen the upper nut (red arrow).
Figure 9

Separate the EGR tube from the manifold by supporting the lower manifold nut with a 17mm wrench and using a'mm wrench to loosen the upper nut (red arrow).

Remove the rest of the retaining nuts and pull the manifold from the head.
Figure 10

Remove the rest of the retaining nuts and pull the manifold from the head. The rear manifold has three separate gaskets, one for each exhaust port (red arrow). The exhaust down pipes and EGR tube do not need additional support while the manifold is off. Installation is the reverse of removal.


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Comments and Suggestions:
Doug Comments: do you mean two hours PER NUT, for the lower manifold nuts reached from below the car? This is a monster job with the cylinder head installed..OMG..Very difficult work. With the head off, not so bad.
May 19, 2016
  Followup from the Pelican Staff: The time quoted is what it took the author or what he assumed it would take a user. Your experience will increase or decrease the time needed. - Nick at Pelican Parts  
Dottie Comments: Going crazy looking for a 1991190e2.3 exaust manifold.

Can you help me?. Thank you. Dorothy. Dotinla@yahoo.com

April 3, 2016
  Followup from the Pelican Staff: I’m not the best with part numbers.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need. - Nick at Pelican Parts
 
quest1966 Comments: The square nuts on the manifolds that attach to the exhaust pipe are fused on pretty hard. Can I simply reuse these without a problem? Thank you.
June 11, 2015
  Followup from the Pelican Staff: I would suggest replacing them. Especially if stuck. Most times these nuts can knocked out, then new ones pressed in. I recall using a punch to knock them out. Going by memory.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
quest1966 Comments: When tightening the exhaust manifold nuts, do they need to be torqued? If so, how is this accomplished with some of the lower nuts? Thank you!
April 26, 2015
  Followup from the Pelican Staff: They should be torqued, you may have to use a special crows foot or extension to get the hard to reach ones.

I would grab a repair manual. It will have the procedure, special tools and torque specs.
- Nick at Pelican Parts
 

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