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Most likely cause, failed Airmatic strut. Replacing the rear takes about two to four hours for most folks the first time, costs under $500 for rebuilt strut with lifetime warranty.
Less likely, but another possible cause is a broken or leaking air line between the valve block and the rear strut. Could be a trivial fix, could be a pain, depending upon where the line has failed.
Also even less likely, but another possible cause, is a faulty air valve in the valve block. Not too tough a job, but you need to do some research on how to do it, if that is the cause.
Thank You for responding to my message. I been reading. I have a great Benz guy. Cross Roads in Weatherford Tx, but there's the monthly budget deal. He is way lower priced than the dealer. Thank You Again...Gary
I would try to do some troubleshooting first. Start with the basics above poster pointed out. Get to the top of it, spray some water/soap and check for leaks. Work your way from easiest to hardest.
I would try to do some troubleshooting first. Start with the basics above poster pointed out. Get to the top of it, spray some water/soap and check for leaks. Work your way from easiest to hardest.
Keep us posted.
Thank you. I made sure it was on level ground last night, and for the first time, I noticed the back passenger side corner was noticeably higher than normal. I will keep you posted. Thank you again. Gary
One possibility is a leaking valve that is allowing unwanted air to over-inflate that strut. There are some threads about refurbishing the valve block on this and other W220 forums.
Sorry I haven't had a chance to look at the Benz till last evening. I spade soapy water on the strut, don't see any leaks, but it changed some. Now, both drivers and passengers side on the rear won't rise. I hear the front pump run and it cuts off like always. I hear a pumping sound from maybe the trunk area that runs a little longer than the front, then cuts off. But the rear of the car is not rising at all. We bought it from a Doctor, had 60k on it. I thank he stated the struts where just change on the rear. Has 100k now, and if anything it sets too much. As you can tell, 40k miles we have driven and we have had her over 10 years now. Being all the good football was Sat, I plan on spending the day at least talking to the old gale,"The Car, not the wife" seeing where that gets me. (-: Thank You, Sir, for the help. Gary
There is only one pump for the Airmatic system, located in the right front wheel well. The pump that you hear running in the rear is the PSE (Pneumatic Service Equipment) pump, located inside the left front corner of the trunk, and which does the door/trunk lock/unlock and soft-close operations, and for the cars that have options, seat cushion inflation, etc.
AFAIK, The only possibilities for air leakage affecting the rear struts are:
- The rolling diaphragms in the struts. These are fabric and rubber diaphragms between an inner and an outer tube in the struts.Leaks here are the most common cause of strut failure. Such internal leaks are extremely difficult to detect by any means, and pretty much impossible to detect with soapy water. Sometimes, if you are in a very quiet area, you can hear a hiss from under the car.
- The air line connection on top of the struts. The nylon lines connect to the top of the struts, inside the passenger compartment. There is a small snap-in cover over the connections on each end of the shelf area under the rear window. A leak here is easy to detect.
- The air lines from the valve block in the right front wheel well back to the struts. Line failure is rare, and can be hard to find. Leaks at the valve block connection are easy to find with soapy water.
- The valves inside the valve block. The only way to detect these leaks is by diagnosis from the symptoms. A leak here may cause the rear to raise while parked, rather than sinking.
If the pump is running and the front struts are maintaining normal ride height, the pump is probably not the problem.
We need a very precise statement of the problem.
"But the rear of the car is not rising at all."
"I noticed the back passenger side corner was noticeably higher than normal."
Once I got it on the level ground the Passages side appears OK. Drivers still not rising. I took a photo of each side, give you an idea of how it looks.
Drivers side that wont rise.
Both photo's the car is running and pump has cycled off.
Very interesting that the left rear is very low, but the rest of the car is correct, and the pump has shut off. This may mean that the computer thinks that all four corners of the car are at the proper ride height.
Important question - are you still getting the red message that the car is low?
I suggest that you carefully check the links from the rear anti-sway bar to the suspension on both sides, and that you check the link in the center of the rear anti-sway bar to the rear ride height sensor. There are three primary ride height sensors - one on each front suspension, and one central sensor on the anti-sway bar. (There are also height sensors for each corner, but those three primary sensors are the normal input for ride height control.)
If you find nothing wrong there, you will need to find someone (dealer, independent Mercedes shop, or individual) who has the STAR/SDS/DAS (all are acronyms for the Mercedes Diagnostic Assistance System, the official computer maintenance system for the car) and who can give you some idea of just what has failed.
First off. Thank you for being patient with me. I drove her to pick up my son tonight. All the way there the RED message was on. As soon as he got in the front passenger seat, it went off. We made a couple of stops. The only message I got was from a stop taking off the traction control keeps flashing no matter how easy I take off. He has the day off so we're going to look at the ideas you posted above. Thank you again. Gary
If the car appears to at or near the correct ride height and you still get the red "car low" message, this begins to sound like a sensor issue. The traction warning is obviously false. I suggest that you find someone who has the Mercedes computerized diagnostic system (called STAR or DAS or SDS) and have them check the car. You will get a full page of error codes - this is normal. They can clear the codes and check again - the ones that come back are the ones that need attention. This won't be free, and may not be cheap, but it is the next step.
You might be able to start a new thread on this forum and on BenzWorld asking if there is an owner near you who has the system and would be willing to help you - there are several owners in Texas. A thread title like "Need diagnostic help from a Texas owner" might do the trick.
We pull rear tires again, used liquid soap to look for leaks. Nothing found. I saw the ride height sensor, appears normal. I pulled up in my yard there is a small rise. The back left tire was just spinning like it was in snow. With the other 3 tires being higher, it appears to take the weight off the back left. Found a link http://www.mercedesmedic.com/ any idea if these lower priced scanners will do what I need to be done. I have a guy that will run a dos test for $80 to $120 and if he doses the work there is no charge for the test. Kerry Moore, https://www.crossroadscarcare.com/
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