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We took our 2007 ML350 into a non-dealer service center that specializes in imports for several service items to be completed: brakes, transmission flush, etc (totaling nearly $2,000). We keep this car in excellent physical and operational condition, and my wife (primary driver) is very careful on the road. After getting the car back, my wife noticed that when she applied the brake, there would often be a popping noise heard that seemed to come from somewhere under the passenger side of the hood. We took the car back to the service center to inspect. They are now telling us that the problem is an upper control arm that needs to be replaced on the passenger side. I thought it was odd that we didn't have this problem until we took the car to them the first time. They said that they did nothing with the suspension and therefore could not have caused the problem, and that it was likely a coincidence. Obviously, coincidences are always possible, but could this have been caused by someone carelessly lifting the vehicle and the suspension settling? They are saying that this is a common problem with Mercedes vehicles. Is that true? They are wanting to charge me $975 (inclusive of taxes and shop fees) to replace both upper control arms. Although only one is making a noise, they say the other one has some play in it and will inevitably start doing the same thing. Any and all thoughts would be greatly appreciated. Thanks in advance!
 

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Im not saying they are wrong, but you have to make sure it is properly diagnosed. The ml's had some issues with the upper control arm bushings making some noise. Are they saying its the bushings making noise or the upper joint where it attaches to the knuckle??? Noises can be tricky to diagnose sometimes, so it would be good to make sure they are 100% sure before you do the repairs Yes, they do have some issues with the arms, but they also had problems with the lower control arm bushings
 

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Zotye Auto 1.5T T600 2016
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Ask them to show you the free play in this control arm. To check an upper control arm joint, lift the vehicle with a wheels free lift. Where the upper control arm joins the upper part of the hub with a swivel joint, hit this with the palm of your hand, a thud and it is OK but a click or worse a clank noise and the joint is finished.

Here is a picture hit with your hand or a rubber mallet where the arrow is;
 

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Outstanding Contributor - Always Remembered, RIP
Zotye Auto 1.5T T600 2016
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I should also add that the ball joint on this model is steel and the arm is alloy, steel is much harder than alloy so wear in the alloy socket is inevitable. Many times I have seen this when a car comes in for work with no suspension noises but once the car is lifted and lowered to the floor the upper control arm makes a noise.

We have to lift the cars to work on them, there is no choice but we are not responsible for the wear and tear factor. However do make sure they have the correct diagnoses and make them prove it.

Parts are expensive but a knock on effect of a bad control arm is uneven tyre wear and tyres are also expensive.
 

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Wow, thank you for all the detailed and informative responses. I had to make a decision on this yesterday because the wife was jumping me about getting her car back. I spoke at length to the tech who diagnosed the problem. It took him five business days to pinpoint the culprit. He had to get some kind of listening ear device to know for sure. He said that one of the the upper control arms was making the noise and that the other one had play. The noise was coming from the knuckle, not the bushing. I had a MB Master on another forum tell me that if the other one was showing signs of play that I should replace both. Just replacing one control arm was going to run me $580, and replacing two was going to be $975. So, worth it to replace both and be done with it now and not have to come back when the other wears out. They said that the control arm part has a bushing on one side and a knuckle on the other, so I am not sure that it really matters which side the noise is coming from, although they are pretty certain it is the knuckle. Not really knowing much about suspensions, it is reassuring to hear that noises can start after a car has been lifted. I suppose that was my biggest worry, that they might have done something before and not wanted to own up to it. I don't have any reason to necessarily suspect that to be the case, but when you are ignorant about something your mind can run wild. I am fairly certain now that when they lifted the car during the last batch of service I had done on the car, that it was the straw that broke the camels back with the upper control arm. I was told and confirmed that the 2002 MLs had control arm issues. So, while I am sure MB worked to improve the quality of their control arms, this doesn't sound like it is an unusual issue. The car has almost 70,000 miles on it, so not brand new either. Anyway, thank you again for all of the information. I am supposed to get the car back on Monday, so hopefully this will fix the noise. Your helpful information has put me at ease ... for now. Thanks! :)
 

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Discussion Starter #6
So, some feedback. I had the local imports garage that I have been using for a few years go ahead and replace the upper control arms on both sides. They charged me $975 to do this, which is a fair price compared to the dealer. I grilled them hard prior to authorizing the work about making sure this was the problem and that it needed to be done. They assured me that the upper control arms were bad, based on their application of a listening ear device. The work was completed the other day and my wife went to pick up the vehicle. She drove it around and the problem persisted without change. Garage decided that it might be the pads they installed a few months earlier -- defective product, especially since this only happens when the brake is applied. They replaced the pads this morning under warranty and believe they have the problem licked. My wife is going to inspect and pick up the car later today. They refunded the $975 for the control arms and apologized for the inconvenience, which I thought was very generous (and the right thing to do). Fingers crossed ...
 

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Zotye Auto 1.5T T600 2016
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So, some feedback. I had the local imports garage that I have been using for a few years go ahead and replace the upper control arms on both sides. They charged me $975 to do this, which is a fair price compared to the dealer. I grilled them hard prior to authorizing the work about making sure this was the problem and that it needed to be done. They assured me that the upper control arms were bad, based on their application of a listening ear device. The work was completed the other day and my wife went to pick up the vehicle. She drove it around and the problem persisted without change. Garage decided that it might be the pads they installed a few months earlier -- defective product, especially since this only happens when the brake is applied. They replaced the pads this morning under warranty and believe they have the problem licked. My wife is going to inspect and pick up the car later today. They refunded the $975 for the control arms and apologized for the inconvenience, which I thought was very generous (and the right thing to do). Fingers crossed ...
That was indeed very generous of them, the new upper control arms will save you a lot of tyre wear but I did say they must be sure of the diagnosis. Here in China it is common for a customer to say OK change the parts but if it does not fix the problem I will not pay and we have to agree.
 

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There a several things on your front suspension that are known problems for making noise. The deciding factor is what type of noise you are hearing. If its a pop metalic type nose when you are braking or taking off from a parking spot. Then it would be a front spindle. There is play between the bearing and spindle housing. If its a grunting bushing type noise over bumps or when braking as the suspension goes down its the lower control arm bushings. If its that later then usually lubing the lower bushings with a wax type lubricant will usually do the trick.
 
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