Steering column bolt loose
05-21-2012, 10:55 PM
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2003 S55 AMG
Steering column bolt loose
With the wheels pointing straight ahead, my steering recently developed a clunking noise when starting a turn (2003 S55, 75,000mi). I found that sitting still, motor on or not, rocking the steering wheel left and right produced the same noise, and I could feel a kind of "notch". Of course I thought of tie rod ends and looked at that, hands on with an assistant rocking the steering wheel. It turned out to be the joint between two steering column sections, held together by a single bolt. Technically, the upper column section that can be (barely) seen in the engine compartment is called lower, and the lowest section that is connected to the rack and pinion unit is called a coupler or coupling.
When the steering wheel was rocked, the two column sections would both move laterally a bit, as the bolted joint flexed, making the noise and producing the "notch" feeling.
This bolt is hard to get at from above but by putting a bunch of socket extensions together and turning the column just right I was able to get a socket on it. It wasn't exactly loose but not real tight either. The MB star DVD service manual, in a disassembly procedure for the entire system, says that this is a bolt that is to be used once, since it is somehow self-locking. As an experiment, I cranked the bolt down pretty good, using a common 3/8 Craftsman ratchet so I wouldn't break it off. This has made the two sections act as one rigid piece, and the noise and "notch" are gone.
However, I wonder if this will last, and if this bolt is really intended to lock the two column sections together by the friction produced by bolt tension, of if the joint itself should fit together tighter apart from the bolt tension. The column sections ends appear to be made in a flat-and-slot arrangement, with the bolt going through all. This kind of joint will naturally tend to be weak in the lateral plane of the flats on the section ends. The purpose of the column is to twist of course, so lateral rigidity is secondary I suppose. But, if the joint works loose, it seems to me that all the movement would make the situation even worse in time.
I intend to get a new bolt at the stealer, and assume that by jacking the car up I will be able to change it from below (there may be a nut to go with it but the joint is dirty and I am not sure). I wouldn't try it from above because I might not get the new one in that way if the column ends separate. I am wondering if there is something wrong with the column section ends, or should I just replace the bolt, tighten, and forget about it? I have never had a steering column problem before so I have no way to judge whether this is serious or not.
When the steering wheel was rocked, the two column sections would both move laterally a bit, as the bolted joint flexed, making the noise and producing the "notch" feeling.
This bolt is hard to get at from above but by putting a bunch of socket extensions together and turning the column just right I was able to get a socket on it. It wasn't exactly loose but not real tight either. The MB star DVD service manual, in a disassembly procedure for the entire system, says that this is a bolt that is to be used once, since it is somehow self-locking. As an experiment, I cranked the bolt down pretty good, using a common 3/8 Craftsman ratchet so I wouldn't break it off. This has made the two sections act as one rigid piece, and the noise and "notch" are gone.
However, I wonder if this will last, and if this bolt is really intended to lock the two column sections together by the friction produced by bolt tension, of if the joint itself should fit together tighter apart from the bolt tension. The column sections ends appear to be made in a flat-and-slot arrangement, with the bolt going through all. This kind of joint will naturally tend to be weak in the lateral plane of the flats on the section ends. The purpose of the column is to twist of course, so lateral rigidity is secondary I suppose. But, if the joint works loose, it seems to me that all the movement would make the situation even worse in time.
I intend to get a new bolt at the stealer, and assume that by jacking the car up I will be able to change it from below (there may be a nut to go with it but the joint is dirty and I am not sure). I wouldn't try it from above because I might not get the new one in that way if the column ends separate. I am wondering if there is something wrong with the column section ends, or should I just replace the bolt, tighten, and forget about it? I have never had a steering column problem before so I have no way to judge whether this is serious or not.
