Steering Column Locking Cylinder Replacment - Mercedes Benz SLK Forum

 
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#1 Old 08-04-2015
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Steering Column Locking Cylinder Replacment - Part 1 of 3

Preface:
If you notice that your steering wheel on your 320 (mineís an 01 but I would think that most 170s work the same) isn't quite feeling stable or locked when you push or pull on it, then itís probably a failing of the locking cylinder which is causing the problem. What has happened ,more than likely, is that a seal on the cylinder has failed and a little bit of fluid has leaked out and/or a little bit of air has leaked in. Since the air is compressible, this allows the cylinder, and therefore the steering column, to move. Very little fluid and air has to make it across this seal for this motion to be noticeably disturbing.

This cylinder is located alongside the lower portion of the steering column on the driver's right. It is very tightly packed in with the other parts and wires associated with the steering column, see the picture labeled 1; and it is mostly hidden under the steering column shroud. The cylinder is threaded on both ends and is held in place by a nut on each end. These nuts can only be accessed by removing the lower panels and the column shroud.



How it is supposed to work:
When the driver pulls on the column release handle, it pushes/pulls on a bell crank system which pulls on a cable. This cable pulls on a control arm on the cylinder, the white nylon shown on the picture labeled A1, which releases a valve inside the cylinder. This allows the cylinder and therefore the column to move. Pushing the release handle back in will release a detent and a spring will pull the cable and the cylinder arm back into place, closing the internal valve; this locks the cylinder and therefore the column.



General comment:
While doing this I already had the instrument cluster removed. Although it may not be necessary, doing so does allow for more room to work. You will have to remove the lower driver's side panels in any case.


So, in order of business . . . (Next post.)

Attached Images
File Type: jpg 1-SteeringColumnCylinder-Mounted-a.JPG (49.9 KB, 11 views)
File Type: jpg A1-CylinderNewOld-a.JPG (31.1 KB, 7 views)
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#2 Old 08-04-2015
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Part 2 of 3

1) Remove the air bag:
In order to remove the air bag unit safely, I needed to disconnect the battery; but before I did that, I loosened the two T30 screws which hold the driver's airbag in place. These are in deeply recessed pockets in the back of the wheel. (Mine are captured to the wheel and should not be able to come out.) Breaking these screws loose took some effort, so being able to reposition the steering wheel was very helpful. (If you have a short-levered T30 driver, this may not be an issue; but I didnít.) At this point, I repositioned the steering wheel straight and level, and with the front wheels pointing straight ahead. I then began to disassembly the column. I found it helpful later on to have the column mostly extended.

Everything I've seen suggests disconnecting the negative side of the battery for 30-60 minutes prior to removing the airbag to allow for any capacitors to discharge. I donít understand the difference between the negative and positive from a safety standpoint for this, so I disconnected both sides ofthe battery to be safe. Since the area around the positive battery terminal is quit tight, and itís difficult to get the cable connector to stay clear of the terminal, I put plastic soda bottle caps over both battery terminals in order to prevent any inadvertent contact. This also allowed me to set the hood back down which was helpful since I was doing all of this in a public parking lot.

After allowing 60 minutes or so to pass, I pulled the air bag module away from the wheel exposing 4 wires that were connected back through the steering column; see the picture labeled 2. You can also see the head of the main attachment screw in the center of the wheel. With the car door open and the module pointed out the door (and no one in front of it!) I pulled the yellow connector from the back of the module. It was quite stiff so it took some degree of working. A wooden or plastic wedge might have been helpful, but I would recommend against using a metal screwdriver blade since any conducted static might set off the bag. USE EXTREME CAUTION in doing this!

I then disconnected the two horn wires and set the air bag module aside in a safe place.


2) Remove the wheel:
First, I tried to note where everything was!! There are alignment marks on the major pieces, so I located those. The center attachment screw requires a 10mm hex (Allen) wrench for removal. Removal of this screw took a lot of force to break it free (itís Loctiteíd in place) so I probably could have used a longer bar. Investing in or borrowing a 16-18" breaker bar or torque wrench, along with a 10mm Allen socket and asocket extension would have been a good idea.

I then braced the steering the wheel; at first by using my knee, but I couldnít get enough leverage on the wrench while doing this. I barely was able to get it loose by standing outside of the car, holding onto the wheel with both hands, and then leaning on the end of the wrench with my knee. Mine took quite a lot of force and then suddenly broke free, so keeping yourself balanced while doing this is a good idea. Also, you do not want to use the steering wheel lock as a block for wrenching since this might damage the mechanism!

I then turned the screw out a few more turns and pulled the steering wheel outwards to make sure it was free. Mine came off pretty easily, but it might have required some rocking. Leaving the screw in a little prevented the possibility that the wheel would come loose unexpectedly and pop me in the face or chest. When everything was reasonably loose, I removed the screw and then pulled the wheel free. The wires can slip back through the hub of the wheel.


3) Remove the Steering Wheel Position Sensor:
See the picture labeled 3. Noting the position of the top plate of the sensor, I had to rotate the plate slightly so I could get to the two Philips head screws which hold the assembly in place. Remove those and then carefully pull straight out on the assembly. It was a little tight, but I didnít want to wiggle it too much, I might have damaged the plastic or the electrical connectors.


4) Remove the shroud, multifunction switch and cruise control:
At that point I could see the top nut of the locking cylinder, but I still didnít have a clear shot to put a wrench on it. I tried a bit of a short cut by pulling the 3 screws from the shroud/switch/control (SSC) assembly, see picture labeled 4, and then rotating the assembly enough so I could get to the nut. Unfortunately, there was still no way for me to get a hold on the cylinder. I turned the nut and the cylinder turned with it. I still needed to remove the SSC assembly in order to have access to the flatted portion of the cylinder body. (So I would have been better off just spending the time getting the SSC out of the way to begin with!)

There are two bundles of wires, one on each side of the column, which prevented me from moving the SSC out of the way easily. I managed to pull enough slack in the bundle on the left side of the SSC, but I had to cut a wire tie (centered under the column) to get enough slack on the bundle on the right. With a little bit of massaging I managed to pull that bundle around the release handle and then pull the SSC over the splined end of the column. I could then twist the SSC to the side as shown in the picture labeled 5.


5) Unbolt the cylinder:
I could then remove the two nuts. On mine, the bottom nut is thick and utilizes a lock washer. The top nut is very thin and uses a beveled/spring type washer. Using a thin wrench to hold onto the flats of the cylinder, I could then break the top nut free. The bottom (or the rod end) of the cylinder is keyed into its mounting flange, so that one came off pretty easily. Compressing the cylinder slightly, I could then take the cylinder free from its brackets.


6) THE HARD PART!!!
To fully remove the cylinder, I had to be able to get the end of the cylinder's arm, see picture labeled A2, to come loose from the cable. The cable has to be pulled through a small slit which runs along one side of a paw at the end of the lever arm. This slit runs at a slight angle to the normal path of the cable. There is also a bead on the cable that limits the amount of free play that you have to work with.

Smaller fingers would have helped; the area is almost completely enclosed on 5 of the 6 sides! I pulled a small pulley loose, see picture labeled B, which sits on the top of the column to give me more free play to work with. It would be helpful to note, or mark the pulley's position first. Iím not sure moving the pulley helped that much because it still took me quite awhile to get the cable to slip through. Eventually I did get it to come loose, but to be honest, I canít say that I know exactly how I managed it.


7) Putting the new cylinder in:
To put the new cylinder in, just reverse the instructions. In my case it worked out a lot easier than the disassembly. I did have the benefit by then of knowing what I had to do.

Attached Images
File Type: jpg 2-AB-SW Attachment-a.JPG (57.1 KB, 7 views)
File Type: jpg 3-SteeringWheelRemoved-a.JPG (61.5 KB, 7 views)
File Type: jpg 4-PostionSensorRemoved-a.JPG (62.7 KB, 8 views)
File Type: jpg 5-ShroudRemoved-a.JPG (72.7 KB, 9 views)
File Type: jpg A2-CylinderLeverEnd.JPG (13.2 KB, 43 views)
File Type: jpg B-Misc-Pully-a.JPG (65.4 KB, 7 views)
File Type: jpg C-Misc-SlideCover-a.JPG (75.3 KB, 5 views)
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#3 Old 08-04-2015
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Part 3 of 3

Other notes:
You will notice that the two cylinders shown in the picture labeled A1, look a little different. I pulled them both to their fully extended positions but they appear to be of different stroke lengths. Perhaps the old one is just broken, but I don't know. The new cylinder/longer stroke does seem to allow the column to extend more fully. In fact, so much so that if I try to fully extend the column, the system will not see the switch that shows that the column has been locked in place; giving me an error light on the dash. This may or may not have to do with the pulley position and I haven't looked at it to see how that particular switch activates. I believe I have the pulley in the right position, but as long as I donít have the column fully extended, the warning light doesnít come on.

When pulling the shroud loose, note that there is a sliding cover on the right side, near the dash, see the picture labeled C. This cover covers the gap where the key lock mechanism engages with the column. Itís very loosely attached to the shroud and easily pops free, you may have to reassemble it if it does. Not a problem, just a pain!

Warning!!! I take no responsibility for anyone following the above description of what I did! If you find something different from how I describe it, stop, check it again and then, if needed, go ask for some professional assistance.

I hope that someone can find the information useful.
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