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Pelican Technical Article:

Resonance Valve Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$7 to $600

Talent:

**

Tools:

10mm socket, 5mm Allen, flathead screwdriver

Applicable Models:

Mercedes-Benz 300CE (1990-93)
Mercedes-Benz 300E (1990-93)
Mercedes-Benz 300TE (1989-92)
Mercedes-Benz E320 (1994-95)

Parts Required:

New resonance valve

Hot Tip:

Remove the air intake pipe

Performance Gain:

Proper idle

Complementary Modification:

Change air filter

The resonance valve on the Mercedes M104 engine is known to be a fragile piece that can be prone to failure. If your car is idling rough there may be a chance that the resonance valve is overly dirty and not functioning properly. Removing and cleaning the valve should be a part of your regular maintenance. Use care when removing the valve as it is very expensive and surprisingly delicate. Once the valve is removed check for a broken shaft or flap. If the shaft or flap is broken you will need to replace the unit.

The resonance valve is located on the left side of the engine between the intake runners (red arrow).
Figure 1

The resonance valve is located on the left side of the engine between the intake runners (red arrow). It is a fragile piece and I recommend removing the intake air pipe (green arrow) to give you a little more room to work. The valve is very expensive. You do not want to damage it when removing it to clean.

Start by disconnecting the MAF sensor.
Figure 2

Start by disconnecting the MAF sensor. The MAF is held in place by two clips to the air filter box (red arrow, one shown one below) a single clamp to the intake tube (yellow arrow) and the wiring harness (green arrow).

Turn the locking ring on the harness (red arrow) counter clockwise.
Figure 3

Turn the locking ring on the harness (red arrow) counter clockwise. This will separate it from the connection on the MAF (yellow arrow).

Separate it from the air filter lid by pulling back on the two clips (red arrows).
Figure 4

Separate it from the air filter lid by pulling back on the two clips (red arrows). Slip the MAF back out from the air filter box. You can leave the MAF attached to the tube and remove the MAF and tube together.

Remove the two 10mm nuts where the intake tube attaches to the valve cover (red arrows).
Figure 5

Remove the two 10mm nuts where the intake tube attaches to the valve cover (red arrows).

Disconnect the air intake temperature sensor (red arrow).
Figure 6

Disconnect the air intake temperature sensor (red arrow).

There is a single hose clamp that holds the intake tube to the throttle body.
Figure 7

There is a single hose clamp that holds the intake tube to the throttle body. You will need to reach between the water pump and the intake runners with a long flathead screwdriver (red arrow) to loosen the clamp. With the clamp loose remove the intake tube and MAF from the top of the engine.

This photo illustrates the throttle body with the rubber bellows (red arrow) and the resonance valve.
Figure 8

This photo illustrates the throttle body with the rubber bellows (red arrow) and the resonance valve. Remove the two rubber grommets from the top of the resonance valve (green arrows).

Use a 5mm Allen and remove the four Allen bolts holding the resonance valve to the intake manifold (red arrows).
Figure 9

Use a 5mm Allen and remove the four Allen bolts holding the resonance valve to the intake manifold (red arrows). Be careful not to drop anything into the throttle body! Some people stuff a rag into the throttle to be on the safe side.

Lift the body of the resonance valve (red arrow) up off the base, separating the vacuum line.
Figure 10

Lift the body of the resonance valve (red arrow) up off the base, separating the vacuum line. Next remove the electrical connection (yellow arrow).

There is not a lot of room between the throttle body tube (yellow arrow) and the resonance valve (red arrow).
Figure 11

There is not a lot of room between the throttle body tube (yellow arrow) and the resonance valve (red arrow). If the shaft from the valve to the flap (green arrow) is broken you will need to replace the valve. Gently lift the base and flap from the intake manifold. There is a rubber seal so it is a tight fit. Take your time and wiggle it out.

Check the condition of the flap (red arrow).
Figure 12

Check the condition of the flap (red arrow). If the flap is broken you will need to replace the valve unit. If the shaft, arm and flap are fine, give the flap a good cleaning and reinstall. Always replace the gasket (yellow arrow) whether you are reinstalling the old unit or installing a new one. Installation is the reverse of removal.


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Comments and Suggestions:
quest1966 Comments: Removing the intake air pipe is not necessary unless the valve is stuck to tightly to work it out using your hands and something to gently pry it up off its base.
November 6, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
jayem Comments: What type of cleaner is safe to use on the plastic parts of the valve?
February 25, 2016
  Followup from the Pelican Staff: Warm water and dish soap. - Nick at Pelican Parts  
Merctech36 Comments: Hi how do I test my resonance valve so I know that it works
November 30, 2015
  Followup from the Pelican Staff: Remove it. See if it moves and returns to rest position. See if you can manually open and close it. - Nick at Pelican Parts  
Merctech36 Comments: Hi my resonance valve's right deep Allen screw go rounded, how do I remove it
November 26, 2015
  Followup from the Pelican Staff: You will have to use a different size Allen, hammer it in. Ir drill the fastener out. - Nick at Pelican Parts  

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