missing steering gear bolts

The seering on my 74 240d suddenly developed huge play. I took a look at it and the steering box is just hanging in there by one bolt. at some point the car has lost 2 bolts. I can see the whole box move as the steering is turned. I need to know the correct bolt size ( dia , pitch etc ) to fix this problem. Any other info that you may consider useful, will be greatly appreciated.

Aazer

[Benzmac]

Order these special bolts from Phil at the number above. They should be torqued to 65 ft/lbs every 15k miles. (This is just one of the many reasons to pay a pro to do the service.)

[Mark DiSilvestro]

I just went through this exercise, last fall, on my 1972 250. The bolts are 10MM, 1.5 pitch(I believe), grade 10.9, 2 of them are about 60MM long and the recessed one is about
25MM long. Check to see if the missing ones have broken off in the box. Also check to see if there is any hairline cracking in the frame rail, around the lowest steering box bolt. I had to install a 1/4 inch thick steel plate to reinforce my frame rail and prevent the flexing which repeatedly caused the steering box bolts to snap. Good luck.

Happy Motoring, Mark

Mark,
Benzmac,

Thanks for the info, the bolts will be here tomorrow, will attempt the job on the weekend.

Mark, about the steel plate you used to brace the frame, is it on the outer side ( wheel well side) of the frame? How is it held in place? Welds or bolts? I dont see any cracks in the area just missing bolts. I have recently acquired this car and the PO had it maintained by some kid ( supoposedly and expert). I had found the main engine mount bolt missing too. I believe that guy wasn't to carefull with bolts he removed/replaced.

Any tips on removing the snaped bolts?

Regards

[stevebfl]

I wrote about this before and may have said more. The real problem is serious. You will undoubtably find the frame cracked. In order to repair it you must understand how it works.

The actual frame is sort of like a 3 by 6 tube of some fairly light gauge steel. Inserted into this tube is a box made of a little heavier gauge sheet and three very heavy tubes. The tubes space the plates so that when the bolts are tightened the channel is not collapsed. The box and tubes are welded together and they are spot welded inside the lighter frame section. By the time the problem exists on the outside the tubes are all broken from the internal box and various cracks occur between the flat sections. The spot welds often are broken. All of these rather fragile pieces form a rigid box when all tied together. Once in pieces rotational loading causes the whole thing to flex and become a parallelagram taking out the new bolts. Ask how I learned all this (bg).

The way I fix the mess is to open a 3in hole in the olutside tube and I weld all the inside components back to one another and to the outside tube often adding boxing strategically (each one is different). I have also repaired this after someone added a 1/4in plate between the original frame position and the steering box. That small amount bound up the box and caused the car to stick any where it was pointed.

This job is probably best done by a welding shop or a metal man in a body shop. Done right it is a major job requiring the steering box removal for starters.

[CarolinaMBZ]

I recently read about this in an old Star article but the covered model years were not addressed. Which model years are covered as far as this being a routine maintenance item?

[Palangi]

Steve. Thanks for another good explaination. My understanding is that this is more common on a 115 than on a 123. Would that be correct? Also, is this failure preventable by properly torquing the bolts at the recommended intervals, or is it more or less inevitable on a 115? Reason for asking is, I am getting a 240D / w115, and would prefer to avoid this problem. Thanks.

[Mark DiSilvestro]

On my '72 250 (W114) I used a 1/4" thick by 6" wide by 8" long, steel plate on the OUTSIDE of the frame rail.
I used 3 galvanized pipe sections, cut precisely to length, as spacers, inside the 3 original bolt holes to transfer the rotational force from the steering box directly to the steel plate. I removed a 1" x 2" section of the broken outer frame wall near the bottom steering box bolt so I could install two 1/8 thick by 1" wide by 4" long steel channels holding 4 metric nuts on the inside of the outer frame wall. The 1/4" steel plate extends down and anchors to the undamaged lower part of the frame rail where I added the channels and nuts. I had to drop the steering box to access the broken bolt stub which was seized into the box. Instead of 2 long and 1 short 10MM bolts, I used 3 bolts, grade 10.9, in the steering box. These bolts are slightly longer than the 2 long original bolts because of the added thickness of the 1/4" steel plate. It's been working fine since last Fall with no more flexing of the steering box or broken bolts.

Someone on the Vintage Mercedes forum said that Mercedes used to have a repair plate/kit availible for some early '70s models - 108 or 107 cars, I think. I don't know if it would fit the 114-115 cars or if it's still availible.

Happy Motoring, Mark

[stevebfl]

I am not sure how many models had this problem. I have fixed them on 114/115 bodies only. I presume that proper tightening of the bolts could eliminate the start of the problem but my impression is that the whole area was just too demensionally instable to not fatigue over time (eventually is a long time).

As to the factory brace. It was installed on 116 chassis cars. I even did one in 1974 or 75 while I worked at the dealer (it wasn't done to fix a problem but to avoid one - maybe a recall or something). I also have one that I have recovered from a scrapped 116 car if anyone ever realy wants to see one. It is a plate (atleast 1/4in thick with three 1/4 in walled tubes welded to the backside. Maybe I'll take a picture later.