Reinforcing The Subframe of a 107

[Philoprof]

As the 107 subframe problem was already discussed here, I was wondering if someone would be kind enough to tell me the best way to go about reinforcing the subframe of my 380sl at this point. I've read about a repair kit with brackets/gussets that can be welded onto the subframe, but I haven't found that kit listed anywhere on the net.

Thanks very much for any advice.

Bill

[230/8]

This a factory recall item and from what I understand is still being honored as a safety issue. I do not recall ever hearing of a kit for DIY repair...probably a liability issue. You may need to shop for a dealer willing to discuss this, or you might contact the zone office directly. Unless your subframe is cracked and beyond repair you can expect only a weld job and gusseting for the repair. Then again, yours may be a model that was modified from the git-go and no repair is needed...the checking in with MBNA will reveal that for you. They kept good records and were able to tell me the date of repair for my own 107 when I asked.

230/8

[Philoprof]

Thanks for the reply. Actually, an MB rep told me a few years ago that my car wasn't affected or covered by the recall, because the problem didn't affect 380's. So I dropped it.

However, a mechanic, who's been working on MB's for over 30 years, told me later that I should have my subframe reinforced anyway, because the 380 subframe is identical to the 450 subframe, and also prone to cracking, -- as some 380 owners have apparently confirmed.

He also said that he could make the reinforcements from regular sheet metal and weld them onto the subframe for less that $200. But he recently retired, and I don't know where to find him.

I was therefore hoping that someone here would know a cost effective solution to the problem. In fact, if I could find the picture of the 107 with a reinforced subframe that I once saw here or somewhere else on the web, I could have my new mechanic make the brackets for me. So if anyone happen to know where that picture is, or have a picture of a reinforced subframe they could post, I'd greatly appreciate it.

[Philoprof]

OK. Here's what my recent investigation into the 107 subframe problem yielded, for anyone who may be interested. First, the following message by a very knowledgeable and experienced MB mechanic appeared in a Mercedes newsgroup some time ago:

"The 380SL is subject to a failure of the front lower control arm rear
attachment to its subframe. This will result in loss of steering control and
likely, a crash. The 450SL was recalled for this problem, and the subframes reinforced by a weld-on kit if still OK, or a whole new subframe if cracks had begun. But Mercedes has never recalled the 380SL, which has the same defective subframe design. Many of them are now breaking, so have yours checked before driving again. "

Bill Ditmire
Ditmire Motorworks,Inc.
425 White Horse Pike
Absecon,NJ 08201
http://www.ditmire.com
609-641-3392

I subsequently called MB-USA, and spoke to a rep who said that they had investigated the problem and considered it closed with the 450sl recall. So, they would not pay to reinforce my 380sl.

I then spoked to the parts mgr at a local dealer who researched the issue and emailed the following info to me:

REINFORCEMANT BRACKET KIT $106.22

ZINC DUST PAINT $113.00

SUBFRAME $1,431.00

BUSHING KIT $ 302.77

IF THE SUBFRAME IS CRACKED AND NEED TO BE REPLACED THE NEW SUBFRAME WILL COME WITH NEW BRACKETS SO YOU WILL NOT NEED THEM OR THE ZINC DUST PAINT BUT YOU WILL NEED THE BUSHING KIT BECAUSE THE OLD BUSHINGS ARE IMPOSIBLE TO GET OUT OF THE OLD SUBFRAME

THIS IS NOT A COVERED CAR UNDER THE RECALL IT ONLY APPLYS TO THE 450SL AND 450SLC

I then went out to see the shop foreman, Dave, at MB of Devon in Philadelphia's Western suburbs, since he has been exceptionally knowledgeable and helpful to me over the years. As it turned out, this was quite a coincidence, since a guy had just brought in a gray market 350sl that MB ended up retrofitting under the subframe recall.

In addition, it was a coincidence that Dave had a 560sl up on the lift. So, he showed me the difference in the strength of that subframe vs mine, and told me where and how to add the reinforcing brackets, requiring about 2 hrs of welding

Another interesting little thing is that the another name for the "ZINC DUST PAINT" that MB sells for $113.00 is ZINC COLD GALVANIZING SPRAY, which ACE Hardware sells in a 14.75 OZ can for around 7.00. (Actually I'm not sure that these are exactly the same, but they're both used to coat metal before welding, and other companies make zinc dust paint for the same purchase.)

So, I ordered the repair kit and 2 bushing kits, and that's where I currently am in resolving this potential problem. When I tackle the job, I'll take and post before and after pictures for people who are considering having the job done or doing it themselves.

[82gray380]

I also just purchased a 82 380sl and after reading this post I am a little concerned about the subframe, but I'm really not sure of what I'm looking for. I found some pictures of a reinforced subframe and mine appears to look like the pictures, but can anyone post some pictures of both the weaker subframe and a reinforced one, so can compare the 2 and see if mine has already been done. It might have already been reinforced, the original owner already had the timing chain changed to the double row and supposedly worked at a MB dealership. Some pictures or a little more detail on what to look for would be greatly appreciated.

[gmo442]

is the 1975 450sl covered under the subframe recall? Would my local dealer know about this and actually fix it for free?

[Philoprof]

Originally Posted by 82gray380

I also just purchased a 82 380sl and after reading this post I am a little concerned about the subframe, but I'm really not sure of what I'm looking for. I found some pictures of a reinforced subframe and mine appears to look like the pictures

Where did you find these pictures?

[82gray380]

On this forum. Do a search for (107 subframe update) and the post with 2 pages on it by roncallo has a set of pictures of a stronger subframe, but not of the weaker model. If you could take some pictures of what yours looks like. As I mentioned before, I'm reallly not sure of what I'm suppose to be looking for. If you could show a picture or two of a weaker model, I could compare and see if mine has been updated or not. Thanks

[Philoprof]

Attached are pictures of my 380sl's subframe. If you compare my subframe to the subframe in the pictures you mentioned, you'll see that the latter has horizontal steel plates welded to the area where the bolts connect the control arm to the subframe, thereby reinforcing the area.

The reinforcements on the 560sl I saw were a little more elegant than these, and included plates that connected the bottom rails to each other. But I'm sure both function similarly.

The interesting thing is that the 560sl has the aluminum engine that MB said didn't stress the subframe as much as the 450sl's iron engine. Yet, MB reinforced the 560sl subframes, but not the 380sl subframes. The incidences of cracking in the 380sl subframe that Bill Ditmier and others have observed seems to support the assertion that MB's failure to recall the 380sl's didn't make any sense.


Regards,

[82gray380]

philoprof,
Thanks for the pictures, they helped clear up my confusion. Unfortunately for me, it does appear that I do not have a reinforced subframe, but everything does look very solid at this time. I will begin to consider my options as far as reinforcing it.
thanks again

[Philoprof]

You're welcome, gray82. Let me and everyone else know how you make out, if you decide to do it.

Regards,

[Richard Wooldridge]

My '82's subframe broke about two years ago while I was taking my granddaughter to school, and I bought the reinforcing gussets from the local MB dealer and also got another subframe from the local junkyard so I'd have a good subframe to reinforce. As I recall, the dealer gave me a break on the price, only charged around $80 for the 4 small pieces of metal that probably cost under a dollar to make. He also gave me a copy of the TSB instructions. One point that was stressed was that the reinforcements MUST be MIG welded to retain the strength of the metal involved. It is necessary to prop up the engine and remove the subframe to fix it.
Performance Parts sells a modified subframe for around $600 that is much better, my '79 has one, and it looks to be much stronger than the reinforced one in my ''82. I took some pix of the parts involved, I'll see if I can locate them.

[Philoprof]

Originally Posted by Richard Wooldridge

One point that was stressed was that the reinforcements MUST be MIG welded to retain the strength of the metal involved. It is necessary to prop up the engine and remove the subframe to fix it.

Rich,

I can't see any reason why the subframe has to be lifted to weld the reinforcements on. Is that what the instructions you have say to do?

Thanks in advance for the clarification.

[Richard Wooldridge]

I suppose a person might be able to do the job with the subframe in the car, but it would be a lot easier to pull it out, clean it up properly, and replace the bushings and motor mounts at the same time as reworking the subframe. That's what I did on mine, and the whole job took under 5 hours to do, one person only. The subframe I got was from an earlier sedan with a diesel engine, so I had to drill access holes for the motor mounts, plus I switched out the control arms on both sides also. I wire-brushed the area before I welded the reinforcements on to ensure nice welds. I also sprayed the subframe before reinstalling it, first with red lead primer in the areas with bare metal, then gloss black. Of course you can do as you see fit, but for me it was much easier to pull the subframe out of the car to work on, and also I switched it with another one due to the damage the one in the car had. (the left rear control arm end tab broke completely off, and the control arm was dragging on the pavement.)

[Philoprof]

Thanks for clarifying this for me, Rich. I'd love to replace the control arm bushings, subframe bushings and motor mounts on my car. But I read in another forum that they can be a *****, and I don't want to open a can of worms that may take me days to close. (See, e.g., the thread at http://sl107.com/eve/forums/a/tpc/f/2346035941/m/5651017182?r=8001073682#8001073682 ). Sounds to me like you must have really known what you're doing to replace all those things in 5 hrs.

Assuming that I'd like to MIG weld the reinforcement brackets onto the subframe with the least amount of difficulty, could you tell me the best way to go about it? That is, can I just support the car, remove the nuts on the control arm bolts, remove the washers, weld the reinforcements on, and then rebolt the arm?

If, OTOH, I want to replace the control arm bolts and bushings while I'm there, how difficult would that be? Can I just support the car on jack stands, drop the control arm, replace the bushings, lift the control arm into place, and rebolt it? Or is the downward pressure of the spring going to make that impossible?

Thanks very much in advance for the advice.

Regards,