SL/R231: Pneumatic Reservoir Failed - twice
Thread Starter
Member
Joined: Feb 2016
Posts: 84
Likes: 19
C300 and SL500
Pneumatic Reservoir Failed - twice
Hi Folks,
On a recent road trip the seat massage functions would not work on my 2013 R231. I asked my indie to take a look. They found the pneumatic reservoir had failed. A new reservoir and line kit and all is good again, but it's the second time they have replaced the reservoir. The failed part was MBZ both times. They said they have never seen this happen before and didn't have an explanation.
There were no codes indicating a bigger problem, just pump over temperature, probably after the reservoir failed. Wondering if you have any suggestion for things they can check to see if there is an underlying problem - pump, sensor, lines, valve, control unit? I would like to avoid another failed reservoir in 3 years time.
I don't think it should make a difference, but we do live at 7200'.
Appreciate your thoughts and thank you
Gary
On a recent road trip the seat massage functions would not work on my 2013 R231. I asked my indie to take a look. They found the pneumatic reservoir had failed. A new reservoir and line kit and all is good again, but it's the second time they have replaced the reservoir. The failed part was MBZ both times. They said they have never seen this happen before and didn't have an explanation.
There were no codes indicating a bigger problem, just pump over temperature, probably after the reservoir failed. Wondering if you have any suggestion for things they can check to see if there is an underlying problem - pump, sensor, lines, valve, control unit? I would like to avoid another failed reservoir in 3 years time.
I don't think it should make a difference, but we do live at 7200'.
Appreciate your thoughts and thank you
Gary
Senior Member
Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Hi Folks,
On a recent road trip the seat massage functions would not work on my 2013 R231. I asked my indie to take a look. They found the pneumatic reservoir had failed. A new reservoir and line kit and all is good again, but it's the second time they have replaced the reservoir. The failed part was MBZ both times. They said they have never seen this happen before and didn't have an explanation.
There were no codes indicating a bigger problem, just pump over temperature, probably after the reservoir failed. Wondering if you have any suggestion for things they can check to see if there is an underlying problem - pump, sensor, lines, valve, control unit? I would like to avoid another failed reservoir in 3 years time.
I don't think it should make a difference, but we do live at 7200'.
Appreciate your thoughts and thank you
Gary
On a recent road trip the seat massage functions would not work on my 2013 R231. I asked my indie to take a look. They found the pneumatic reservoir had failed. A new reservoir and line kit and all is good again, but it's the second time they have replaced the reservoir. The failed part was MBZ both times. They said they have never seen this happen before and didn't have an explanation.
There were no codes indicating a bigger problem, just pump over temperature, probably after the reservoir failed. Wondering if you have any suggestion for things they can check to see if there is an underlying problem - pump, sensor, lines, valve, control unit? I would like to avoid another failed reservoir in 3 years time.
I don't think it should make a difference, but we do live at 7200'.
Appreciate your thoughts and thank you
Gary
https://mbworld.org/forums/sl-class-...lfunction.html
All seat pneumatic functions on both seats would stop, but then work again after the motor cooled and reset itself.
Are both seats affected? Does the system (massage) come back online once the vehicle is turned off for awhile? If so, it may point to a leak somewhere in the system causing the motor go into a protection mode.
I'll also add that I've been told the massage function may normally shut down after about a half hour or so of use. I cannot verify as I don't normally use massage.
Good Luck!
Last edited by hornethandler; May 18, 2025 at 01:45 PM.
Senior Member
Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Further to my last (above).
Here's the electrical function schematic for the multicontour seat.
I don't recall there being a "pneumatic reservoir"; do you have a part number?
Here's the electrical function schematic for the multicontour seat.
I don't recall there being a "pneumatic reservoir"; do you have a part number?
Last edited by hornethandler; May 18, 2025 at 03:49 PM.
Thread Starter
Member
Joined: Feb 2016
Posts: 84
Likes: 19
C300 and SL500
Thanks for the replies.
The problem has been diagnosed and fixed. The leak was due to the failed pneumatic reservoir. Yes, the pump shut down with an over temperature code when the rese1rvoir failed. None of the seat functions worked or came back on line until the reservoir was replaced. Everything now works.
The part number for the reservoir on the invoice is 000-800-29-19. It's part of the pneumatic side of the system and probably passive, so it likely wouldn't show up on the electrical diagram. As I understand it, it is a reservoir between the pump and the downstream systems. It stores air at pressure so the pump isn't driving the seats etc. directly.
What I'm wondering is if anyone has a suggestion as to why the car has now blown two reservoirs? Seems likely that the pump occasionally drives too much air into the reservoir. I wonder what the most likely cause might be - a sticky valve, a dodgy sensor, a bad control unit?
The indie didn't see any codes that indicated anything untoward so they replaced the reservoir, perhaps treating the symptom rather than the cause? I would like to investigate the cause so the symptom doesn't return. So far it only happens once every few years, so not an easy one to track down, but at over $600 in parts - reservoir and line kit - plus labor, it's an expensive repeating repair for a rarely used function.
Thank you
Gary
The problem has been diagnosed and fixed. The leak was due to the failed pneumatic reservoir. Yes, the pump shut down with an over temperature code when the rese1rvoir failed. None of the seat functions worked or came back on line until the reservoir was replaced. Everything now works.
The part number for the reservoir on the invoice is 000-800-29-19. It's part of the pneumatic side of the system and probably passive, so it likely wouldn't show up on the electrical diagram. As I understand it, it is a reservoir between the pump and the downstream systems. It stores air at pressure so the pump isn't driving the seats etc. directly.
What I'm wondering is if anyone has a suggestion as to why the car has now blown two reservoirs? Seems likely that the pump occasionally drives too much air into the reservoir. I wonder what the most likely cause might be - a sticky valve, a dodgy sensor, a bad control unit?
The indie didn't see any codes that indicated anything untoward so they replaced the reservoir, perhaps treating the symptom rather than the cause? I would like to investigate the cause so the symptom doesn't return. So far it only happens once every few years, so not an easy one to track down, but at over $600 in parts - reservoir and line kit - plus labor, it's an expensive repeating repair for a rarely used function.
Thank you
Gary
Senior Member
Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Interesting…
The only obvious thing is a reservoir over-pressure causing it to crack, or maybe a rupture from an object piercing the tank from where it’s mounted. Do you have the old reservoirs? Did they fail at the same location? Worst case, can you repair them?
I’d be looking at the pump itself for a mounted, or downstream pressure switch/regulator. If there is one, it might be possible to clean it up in case it’s sticking.
As you surmised, it’s likely a “sticky valve, a dodgy sensor, a bad control unit”.
# 11 on the electrical schematic refers to a “pressure sensor signal”; however, it appears related to the seat functions and not the pump itself.
Good luck and keep us in the loop.
The only obvious thing is a reservoir over-pressure causing it to crack, or maybe a rupture from an object piercing the tank from where it’s mounted. Do you have the old reservoirs? Did they fail at the same location? Worst case, can you repair them?
I’d be looking at the pump itself for a mounted, or downstream pressure switch/regulator. If there is one, it might be possible to clean it up in case it’s sticking.
As you surmised, it’s likely a “sticky valve, a dodgy sensor, a bad control unit”.
# 11 on the electrical schematic refers to a “pressure sensor signal”; however, it appears related to the seat functions and not the pump itself.
Good luck and keep us in the loop.
Senior Member
Joined: Jan 2019
Posts: 480
Likes: 158
From: Philadelphia area
2014 SL65 AMG, 2018 S560
I had a similar issue with my 2014 SL that turned out to be leaky hose connections at the pump. What I found is there are o-ring seals in the hose connectors at the pump that were dried out causing air leaks. I lubed the o-rings with silicone and it's been fine ever since.
So I guess my question is whether they definitely established that it was a leak in the reservoir. Was there a visible crack or did they do a leak test of that part?
So I guess my question is whether they definitely established that it was a leak in the reservoir. Was there a visible crack or did they do a leak test of that part?
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Senior Member
Joined: Jan 2019
Posts: 480
Likes: 158
From: Philadelphia area
2014 SL65 AMG, 2018 S560
I've heard that it's a problem and was expecting the same when I was troubleshooting my car. Just a wild guess but is it possible the pump is over pressuring? Not sure, but I think the pressure sensor is built into the pump.
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Senior Member
Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
I just reread your first post and saw something you posted that I missed first time around.
“we do live at 7200'”
I’m wondering… could your reservoir be failing from differential altitude pressure rupture?
When I realized that you’re at 7,200 feet, I wondered how that pressure altitude would affect the integrity of the reservoir.
I have limited experience with pressure/altitudes, but it was apparent that a height of 7,200 feet was significant enough to explore.
The knowns are that internal reservoir pressure are unaffected by atmospheric pressures changes; however, outside pressure changes have a significant effect on the integrity of the reservoir. The differential pressure between sea level and 7,200 feet equates--according to google--to about 2,5 times less pressure acting on the outside of the reservoir than at sea level. Although this differential pressure is not excessive--according to google the safety margin is 3 to 4 times for pressure vessels--it’s close to 3 and in my humble opinion is close enough to warrant consideration.
If you believe your elevation could be the cause, a suggestion would be to wrap your next reservoir in fiberglass to strengthen the exterior.
I hope all works out well
“we do live at 7200'”
I’m wondering… could your reservoir be failing from differential altitude pressure rupture?
When I realized that you’re at 7,200 feet, I wondered how that pressure altitude would affect the integrity of the reservoir.
I have limited experience with pressure/altitudes, but it was apparent that a height of 7,200 feet was significant enough to explore.
The knowns are that internal reservoir pressure are unaffected by atmospheric pressures changes; however, outside pressure changes have a significant effect on the integrity of the reservoir. The differential pressure between sea level and 7,200 feet equates--according to google--to about 2,5 times less pressure acting on the outside of the reservoir than at sea level. Although this differential pressure is not excessive--according to google the safety margin is 3 to 4 times for pressure vessels--it’s close to 3 and in my humble opinion is close enough to warrant consideration.
If you believe your elevation could be the cause, a suggestion would be to wrap your next reservoir in fiberglass to strengthen the exterior.
I hope all works out well
