S_W222

I recently encountered an issue with my car's dynamic seats just yesterday, which included a hissing "air" leak sound and the seats becoming inoperable. I was able to identify and fix the problem, and I wanted to share the solution with all of you to benefit from my experience (This issue could potentially affect any of you when parking your cars under the sun on hot days)

Symptoms:

1. Hissing noise "air leak": Upon starting the engine, I immediately noticed a hissing sound coming from the passenger seat.
2. 5-10min later, Hissing disappeared, seats inoperable: After about 5 minutes, the hissing sound stopped, but the dynamic seats (lumbar adjustment, massage, etc.) were no longer functioning. It became evident that the air pump had shut off due to detecting a continuous air leak.

Cause:

1. High temperature inside the vehicle: The temperature inside my car reached nearly 155°F (68°C) after parking it under the sun on a hot 95°F day.
2. Poor design: The issue stemmed from a lack of insulation between the PVC air tubes and the metallic seat recline motor, which (I believe) caused heat conduction and then initiated the melting of the tube in contact with the motor. (See photo #1 and #2 below).

Solution:

1. Removing the back cover of the passenger seat: I followed these steps to access the seat's inner components: Steps: Remove 2 bolts at the bottom of the cover --> Pull the clips next to the bolster out --> Gently pull the cover backward by about 1-2 inches --> Pull downward and apply controlled force to release the upper clips (the most challenging part). (see image # 1)
2. Locating and repairing the leaking tubes: I found the air leak was originating from a melted section of the PVC tube connected to one of the lower lumbar air bladders. I cut/trimmed out the damaged portion, approximately 0.5 inch in length. (see image # 2)
3. Finding a suitable replacement coupler: I purchased a 0.75" (3/4") coupled for 3/4" O.D. PVC tubes from LOWES. I opted for a 90-degree elbow coupler to guide the tube naturally without bending it forcefully like factory did. This coupling piece basically connected the remaining intact portions of the PVC tube around the damaged area that I trimmed. (see image # 3)

Prevention:

1. Addressing the design flaw: as I mentioned, this problem may affect any W222 when parking your cars under the sun on hot days. I believe it's a design oversight. The metallic parts, such as the seat motor, and the PVC air tubes should have been insulated from each other. (see image # 4)
2. Applying insulation to the seat motor: To mitigate future overheating, I used X-Protector, a fiberglass-like material commonly used for scratch resistance on chairs (available at Walmart/Lowes/Amazon/anywhere). I wrapped the metallic seat motor on the side facing the tubes, leaving the other sides exposed for heat dissipation. (see image # 5)
3. I also identified the same design flaw in the driver's seat and repeated the insulation process. hopefully this can avoid any further incidents of overheated tubes on the driver side too.

Attached Images:

• Image #1: Removing the back cover of the passenger seat.
• Image #2: Location of the melted and leaking PVC tube.
• Image #3: Replacement coupler used for repairing the PVC tube.
• Image #4: Photo showing the need for insulation between metallic parts and PVC tubes.
• Image #5: Applying X-Protector to insulate the metallic seat motor.
• Image #6: Finished product

• 
  removing the back cover of the passenger seat
  
  Location of the melted and leaking PVC tube.
  
  Replacement coupler used for repairing the PVC tube.
  
  The need for insulation between metallic parts and PVC tubes.
  
  Application of X-Protector to insulate the metallic seat motor.
  
  Finished product

I hope my experience and the provided solution above can be helpful to those facing similar issues with their dynamic seats.

retatt

Impressive!!

S_W222

@MB V MB V This would hopefully help you out with issue you are having with your seats. See above.

MB V

My hoses are run much differently. I’m still trying to find a photo or diagram where some of the hoses are routed. I’d like to replace two of them, but unable to see where they go when they enter the bottom right corner of the left seat.


I’ve repaired the red hose using a Sharkbite and new 1/4 inch hose. The green and clear ones are actually a smaller diameter. They were either cut or broken from age. I tried shrink wrapping those two, but it didn’t work.

S_W222

They usually goes right into one of the so many air bladder. If that's where the cut or leak occurred (Close to the air bladder), then you would be dealing with a very serious repair here. It is really complicated to get to the front side where the air bladders are if that's where the cut and leak is. See this video below, it shows how the structure of the air massagers and air bladders look like (I copied the video link to skip right to the point wherein the air bladers and tubes are shown). If that's where the cut is, depending on your hand-skills, you may want to take the risk of trying to remove the entire seat leather and all other layers, or take it to an upholstery automotive-shop and let them help you out with that task, and then complete the repair yourself. I would then seal all cracked or weak tubes the same way I did, or actually get new tubes and wrap them against any potential thermal contact with metal.

MB V

Thanks for the video. However, my car is an 2011 E-350 Cab. Totally different seats. I cannot find the junction box where all the hoses connect as in the other photos and video. It is possible it’s behind the foam. In which case I’ll leave it broken. But I’m not convinced it’s there.