What's This Captive Nut For in W123 Interiors?
 

Y'all,

While doing the thorough cleaning of my 300td's interior, I removed the seats and noticed a hole in the carpet on the sill, a bit forward of where the lower end of the seat belt attaches. There's a captive nut underneath, in maybe a 10x1.25mm thread size. Thus, it's too small to make it an alternate location for the seat belt attachment point. I made a point to look for this "feature" in the W123s in the junkyard the last time I was there, and they all had this hole with the captive nut underneath. What is this for?

Thanks,
Shawn

I've asked the same question before, and didn't find any kind of definitive answer. The best possibility is that something bolts there that may be related to the seat bracket on some models. If you figure out why it's really there, please share.

I may have found the answer to that one. There was a Euro wagon at Pick N Pull, and it had great MB-Tex front seats. {which are now in my wagon ;)} The passenger seat had a totally different base. The seat would adjust front and back on a slide, but it had no up and down adjustment capability. So the seat was fastened at 4 corners like a normal seat, but there was also a long bolt that attached the outside base of the seat to the side floor frame right next to the seat belt anchor point. Was a long sleeve bolt. So I assume that is also a possibility for the driver's seat.
I just had to replace the passenger seat bottom mechanicals with my old seat.

Both of my W123 240Ds have a long 6mm bolt, washer and spacer anchoring the front passenger seat's rear-leg to the sill. I presume it's because the tall passenger seat mounting legs don't have the same side-rigidity as the drivers seat gets from it's stacked fore & aft/height adjusters.

Happy Motoring, Mark

So, Mark, what you're saying is that the 240D front seats are not a mirror image set like the 300D. Of course the arm rest also figures in making the seats different, but in a different way. That is interesting news, as I have not had a 240D in the W123 chassis. Seems like it might limit the "swapability" when looking to upgrade front seats.

I never realized there was a difference in the seats either, but in terms of "swapability" as you say, just change the seat bottom mechanicals over as Jimmy said, the seat buns/frames are still the same. Also you can take the bottom seat portion on a w123 and use it on either side of the car, not so with the seatbacks though.

Extra strenght?
 

My 81 240D has that long bolt on both front seats. I always assumed it was simply for extra strength in anchoring the seats. I replaced my 240D's seat with one from a 300D which had an armrest and it just bolted straight in.

- Peter.