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It’s my first post on MBworld. I’ve owned a W212 for five years and recently added a r231 SL550 with 58,000 miles to my parking lot. It’s a super clean car from a private seller with all the bells and whistles, including dynamic seats. However, I realized that the multicontour seats only work for about 10 seconds after a cold start and stop working due to leaks, making a hissing sound. It’s bummer cuz I love this feature and was one thing I was looking to have in this car. I took it to my mechanic for some preventative maintenance and asked them to fix the leak. They diagnosed the issue but said it wasn’t within their wheelhouse to fix it, so they gave up. They also mentioned that my pump was overheating. So, now I apparently have to replace the pump and fix the leak. I’m willing to spend some money to have it fixed the right way, or if there’s a good DIY for me to do it myself. Unfortunately, I couldn’t find any videos for the r231 on the internet.
Here's a link with some useful info., including documents for the seats.
The pump shuts down to prevent overheating when a leak is detected. Hopefully that's the reason the pump is getting hot and not because of a bad pump.
Recommend fixing the leak before replacing the pump.
It’s my first post on MBworld. I’ve owned a W212 for five years and recently added a r231 SL550 with 58,000 miles to my parking lot. It’s a super clean car from a private seller with all the bells and whistles, including dynamic seats. However, I realized that the multicontour seats only work for about 10 seconds after a cold start and stop working due to leaks, making a hissing sound. It’s bummer cuz I love this feature and was one thing I was looking to have in this car. I took it to my mechanic for some preventative maintenance and asked them to fix the leak. They diagnosed the issue but said it wasn’t within their wheelhouse to fix it, so they gave up. They also mentioned that my pump was overheating. So, now I apparently have to replace the pump and fix the leak. I’m willing to spend some money to have it fixed the right way, or if there’s a good DIY for me to do it myself. Unfortunately, I couldn’t find any videos for the r231 on the internet.
If you can hear the air escaping inside the car then you probably do have a leak inside the seat. Could be a seat bladder or one of the hoses connecting to the bladder. The panel on the back of the seat comes off and that would be the starting point for finding the leak. You should be able to find videos on these forums for how to disassemble the seat. Depending on what's leaking you may have to remove the seat. Probably why your mechanic didn't want to get involved.
The pump itself is designed to handle some fairly high temperatures so don't assume it's defective, especially if it's still pumping air. They're very expensive so don't replace it if you don't have to. For sure you should tend to the leak because that's what ultimately destroys the pump.
I have this exact issue! My code also states that I have an overheating pump. Now I am not sure if I do have a leak, considering that the seats do work for the first minute the car is started and do maintain its pressure in the seat once the pump stops working, however, when I scan my car, it shows up as an overheating pump. Your car might not have an overheating pump at all as there is a chance that you just have a leak and not an overheating pump. Nonetheless, I have the exact same issue as you and I would love an update to your issue as I also need to get mine fixed.
I have this exact issue! My code also states that I have an overheating pump. Now I am not sure if I do have a leak, considering that the seats do work for the first minute the car is started and do maintain its pressure in the seat once the pump stops working, however, when I scan my car, it shows up as an overheating pump. Your car might not have an overheating pump at all as there is a chance that you just have a leak and not an overheating pump. Nonetheless, I have the exact same issue as you and I would love an update to your issue as I also need to get mine fixed.
Here's a simple test you can perform to check if the side bolsters are leaking.
Sit in the seat and inflate the side bolsters to level "10." After they are fully inflated, wait about a minute to feel if they begin to deflate—you would feel it on the side of your arm. The deflation might be subtle—as it was in my experience (drivers side left bolster only)—but even a slight decrease can trigger a fault that shuts down the motor and disables all active seat functions. If this happens, allowing the car to sit for a while will enable the pump to reset, and the active seat functions should resume.
I have this exact issue! My code also states that I have an overheating pump. Now I am not sure if I do have a leak, considering that the seats do work for the first minute the car is started and do maintain its pressure in the seat once the pump stops working, however, when I scan my car, it shows up as an overheating pump. Your car might not have an overheating pump at all as there is a chance that you just have a leak and not an overheating pump. Nonetheless, I have the exact same issue as you and I would love an update to your issue as I also need to get mine fixed.
If your seats maintain pressure then the leak may be in the trunk. I had a similar problem with my 2014 SL. In that case it was the hose connectors to the pump that were leaking. A rubber seal in the connectors dried out.
The pump sits in a foam cradle and is not otherwise fastened down. Remove the foam lid and gently lift the pump slightly out of the cradle. If you hear hissing noises then you probably have leaks at the connectors. There's a small o-ring inside each connector. I fixed it by treating those o-rings with some silicone grease. The same stuff used on weather seals would also work.
The other possible source of a leak in the trunk is a cracked reservoir. It's a plastic container that sits next to the pump.
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