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location of reed valve

Mercedes Benz Reed Valve Problem and Solution S R Class

Reed Valve Problem

locate reed valveNo matter the kind of engineering carmakers pour into creating their masterpiece, achieving perfection in cars may still be hard to achieve, Mercedes-Benz is no exception!

Reed valve flooding is a known problem of several Mercedes-Benz luxury models including S430, CL500, S500, R350, and R500. A reed valve is located in the engine compartment, near the firewall. It regulates the flow of collected rain. It is located on the cowl and controls the water that drains into this area.

It can get clogged over time because of debris, such as leaves or pine needles, which are accumulated in that area. When a reed valve is clogged, fluids then overflow into the passenger compartment.

How do you know the reed valve is defective or clogged?

Once the reed valve gets clogged, the inside of your car on the passenger side gets wet even from a light drizzle. The water comes from the glove box area and into the passenger compartment—the cowl, cabin, and carpet.

Where is the reed valve located on Mercedes-Benz S-Class W220?

It is located on the cowl and controls the water that is collected by it.

reed valve location mercedes w220Mercedes Reed Valve Flooding Problem Solutions

Inspect the reed valve

If you regularly inspect and clean the read valve from debris and leaves you can avoid future problems. You can use a long screwdriver or stick that you can get through the screen to remove any debris on the reed valve.

clean reed valve mercedesRemove the reed valve

You can either replace the reed valve or if you don’t have a replacement reed valve. Your other options are to remove or drill a hole next to the existing hole. The picture below shows you where the reed valve should be located. location of reed valve

How will it affect the car?

jump-start-mercedes-s-class-w220-12Having water in the passenger compartment is unfortunate and causes electrical malfunctions. It can cause shorted fuse, damaged control units or it may cause current overload.  Common problems include unnecessary error messages.

What can you do about it?

The simplest way to deal with this problem is to clean the cowl and the reed valve itself. To do it, follow these steps:

  1. Open the hood.
  2. Locate the fresh air intake and the covering plastic grate.
  3. Remove the cover by using a flat medium-sized screwdriver, releasing the clips that hold the cover.
  4. Take out the debris that clogs the valve. If necessary, flush it with water or blow it with compressed air.
  5. Put back the grate and clip it in place.

In some instances, you may also need to drill a hole for the water to drain or remove the reed valve completely to let the water out.

To avoid this hassle in the future, make it a habit to check the reed valve regularly for any debris that leaves around it. Doing so will rid you of possible headaches due to damaged car parts and unwanted water in the passenger footwell.

Did you know?

Mercedes-Benz was sued for Reed Valve Water Leakage. In 2010, a settlement was reached. If you own a 2001-2006 model of MB S-Class or CL-Class, and you are experiencing this problem, you could have been entitled to benefits if you submitted a claim within the specific time frame. You can check out this site for more information: Read Valve Class Action Lawsuit.


  1. Hello
    i have a mercedes 230clk mod 1999, when i drive in an ascendant road i get a very high temperature arround the gear stick and i notice that limping happen and the gear doesnt working properly while the fluid is correct ,in addition the outside temperature mark very high too.

    • i did search all around the engine there is no filling tube goes to transmission housing just engine deep stick will you please tell me where it could be

      • Depends on the MB model that you have but it should be near the firewall. It may be a short tube so you have to look down there.

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