Dealership says their techs do. Which does not mean you have to. Torque specs include angle measurements on many of these, which implies TTY, which suggests replace.
I didn't buy new fasteners when I ordered my control arms and am tempted to just re-use old ones. The GM mechanic I know would probably tell me that's okay.
What is the consensus among MB owners?

 

I changed all of my control arms and used the same fastners. WIS did not ask for new fastners and gave typical torque settings, no torque to yield for my W164. Post your VIN and Ill have a look at WIS and see what is says for your car.

 

Perfect, vin is WDBUF72X98B228774
I just torqued mine to 50 Nm plus 120 degrees, following the FCP Euro W211 youtube video.

 

Here's quite a few documents that deal with the front end of your car. Hopefully somewhere there you find the answer.

 

Also, helps if you put your VIN in your profile - people will respond with the WIS docs voluntarily

 

Thank you for these documents and the suggestion. I have added my VIN to my profile.

“Notes on self-locking nuts and bolts” requires all self-locking fasteners to be replaced after single use except for those with blue encapsulated threads (D in the document). However, the photo description given for self-locking nuts looks different than the nuts on my car which have an uncontinuous protroding rim around the top out nut surface.

The document on spring control arm on front axle lists as self-locking the nuts for the front axle stabilizer bar, and “wheel location, hub” to stub axle and front axle carrier with torque specs 50 Nm plus 60 degrees, and then 80 Nm plus 120 degrees which are probably the fasteners I was messing with last night. Since these are listed as self-locking although they don’t have any vinyl that I can see, I can only guess that they are single use. I have to guess because the literature is not strictly conclusive.

Also, even despite the implication that these fasteners are single-use, I wonder if it’s necessary.
I’ll be driving to the dealership to get an alignment. Do they loosen the control arm bolts to adjust camber? If so I might just ask them to replace the bolts while they’re at it for another thousand dollars or so.

 

Yes. Suspension, steering and brake fasteners are safety critical single use parts. Replace them. Don’t corner cut the expense.

 

Do the control arm bolts get loosened and then re-tightened during an adjustment, for camber?
If they are truly single use, I wonder if they replace these bolts at every alignment?

I called the dealership and they answered this question. They don't remove the bolts for alignments. Single use to them means if you're replacing the component, replace the bolt, but the bolts can stand to be loosened slightly for the scope of an alignment and then re-tightened. I asked whether it's better to show up with my old bolts and have them put new ones in and they weren't keen on it, said they don't normally remove the bolts and would rather not mess with it. So I'll be ordering new bolts and nuts for the control arms. I'll do a visual check in case there are any other lock nuts I may have missed and go back and replace those too. Thanks guys for your feedback.

 

Read WIS and report back.

Dealer is not MB. Dealers care for nothing else than their pocket and flipping cars through the service bays.

 

Thank you. It sounds more likely that the bolts should be replaced. I just placed an order for 4x front and rear lower control arm bolt kits #0003300018, 4x upper control arm bolts #000000002483, and 4x upper control arm nuts #000000005268 for $200 from FCPEuro. I will replace them and then drive to the dealership for an alignment.

 

Here's one for you...as you'd imagine, WIS states not only to replace our subframe bolts, but also to re cut or chase the threads of the frame floor and blow them out with air. Now wouldn't you know that the only job I haven't done myself (rear subframe replacement), which was done by a MB Master tech & former Dealership shop foreman (now running his own Indy shop) reused ALL of my old hardware?!

This attitude is not only shared amongst your GM friends. When I ask Euro car specialists alike, I always get this lax response often ending in, "well technically you are supposed to replace it al, but...". Needless to say, I have new hardware that will be installed properly as I do all of my rear arms. I've (ignorantly) reused old hardware on front struts & sway bar, now going on near 5 yrs & close to 50k mi without issues. I do have the new hardware now though as well as have been using it whenever/wherever I can. At a minimum, new nuts and cleaning threads of old bolts which I know is not perfect, but here we are.

I've received 2 different types of locking nuts from MB and/or FCP :


With nylon insert

Without nylon insert

Interestingly specific to the same applications, control arm/suspension arms although the nylon inserts may have only come from MB for the piston on top of my rear shocks. I often hear everyone say the reverse threaded bolt for our oil drip pan/centrifuge is 1 time use, yet I just looked at the WIS document which does not say that. I'm still replacing it. Perhaps those who are more simple minded and never give such things a thought are better off. I'm not sure hahaha

 

I re-use most of the hardware depending on its condition. For example the brake caliper bracket bolts the manual says never re-use, though I have removed the brackets 2-3 times now and re-used the bolts. Had the springs control arms off twice and re-used everything. I bought a set of used rear shocks and I re-used the hardware that came with them because they looked to be in better condition than what was on the car. Cant forget the wheel bolts, i'm always re-using those. Then I save anything that I think is still usable, bag them with the part#. I'm finding most hardware is just for certain things, though the sway bar link nuts are used a few different areas.

Transmission pan bolts is one thing I made sure to buy new and I used a new drain plug just because I replaced the pan and it came with one. Oil drain plug i've re-used a few times when I dont suck up the oil from the dipstick. Front and rear diff plugs I re-used. Always installed new washers where they are used.

I plan on replacing the rear control arms so will be lowering the subframe, I will be buying new subframe bolts for that and will follow the manual where it says to recut the threads and blow out the holes. All the hardware looks in less than ideal condition so will be buying all new.

I bought a bunch of the most common plastic fasteners and nuts which come in handy. Push pin part# 1249900492 and plastic nut part# 2019900050 both are used in the wheel well liners, the nuts will also work to replace damaged/missing nuts holding the long undertrays under the car. I've even used the nuts to hold up the heat shield over the mufflers where the metal ones rusted to nothing, see how long they hold up since the metal ones that belong there are $4/each. I've also been replacing the screws and metal clips that hold up the 3 undertrays in the front below the engine, those are just so worn they rattle loose.

 

I'll correct myself on this - I did change the fastners - just not the bolts.

 

If you pay attention to WIS, there is always a guideline bulletin about one-time use nuts at the beginning of any suspension parts removal instructions.
If it's a nylon crown nut, replace it. If it came with solid glue, replace it. If it's bare steel, you can reuse it.