E320 Wagon Subframe bolt broken!!
 

So I was trying to change the rear subframe bushings & accumalators on our E320 wagon.

One of the bolts on the subframe (the drivers rear bolt) was corroded badly. I tried PB blaster for a couple of days, but still managed too snap it off. About 2-3" of the bolt is still in there.

Anyone ever had this problem or think of a solution? The car is not in a location where its easy to drop the subframe completely. I have done it on a 500E before twice, so I know how to do it but as I said, its not somewhere I can do it. How can I move the car, with only 3 subframe bolts attached?

That missing bolt isn't a concern if you're moving the car on your property.

Man that sucks! I feel for you. I've found that there's so much Loc-Tite (or whatever the MB factory equivalent is called) on subframe bolts, it's a miracle that they ever come out in one piece. I can't offer any advice other than to do whatever it takes to get the broken bolt out. We don't do many subframe bushings, but when we do, it's almost always necessary to repair the threads in the body, which tend to get torn up pretty good when the bolts are removed.

That's unfortunate but you probably have to get it to where you drop the whole rear suspension (if the broken bolt allows) so you can work on removing the broken bolt. Drill a small hole and use an easy out or drill it dead center with increasing larger drill bits trying to save the threads. Using heat may help too. A shop will have the lift to get to it easier.

Many thanks for the suggestion. What did you end up doing with your Renntech 103 motor? We emailed a couple of times about it, once on mbworld & the other on ebay.

david

Hey David,

I just removed it from the chassis so I can make room in my driveway. I put it up for sale from time to time on CL. A local buyer was a day from picking it up but decided he didn't want to deal with adding smog equipment. Otherwise I'm saving it for my 300CE if that motor ever quits.

thats no big deal....I wouldn't go racing around but you certainly move the car....is the broken bolt (without the nut) facing up?

Stamford CT? I just saw that...I dig Stamford....Been there many times on business trips....I could see living in Stamford.(Fairfield County right?)...good for you..ever been to Cobbs Mill Inn on the Waterfall? Up north of Stamford on that turnpike or parkway...the one that every bridge is different cause they were built in the new deal era by local builders? That's nice territory there....

Can you access the broken bolt piece easier from the trunk side? I think it reaches though.

The bolt is broken off almost exactly where the threads start. Which makes the end of the broken piece that is in the car recessed about 1/4 inch above the "sleeve" that protudes from the body.

So, as the broken piece doesn't "stick out" I can't just heat it & put a big vice grips on it. The only way is going to be drill it out or an extractor.

Cobbs Mill Inn is in Weston Ct, about 15 miles up the coast. Its not called New England without good reason, although a little warmer would be nice.

I was just thinking it might be easier to work from the trunk side to drill out. One possible alternative could be to replace the threaded plate. I think the repair method is to break the spot welded one off and rivet the replacement in. I guess you would need to prime & re-seal as well.
I know the shop manual says to tap those threads before re-installing the bolt(assuming you re-use the threaded plate), so I guess it was a problem area.

Eazy-outs will not work if that bolt is loctite-d and rusted,
Center punch first most accurately, center drill secondly, the first drill about 1/4 Inch diam (one of those extended length types) to get the visual alignment as close as possible.
Step up sizes of drills to tap diameter and tap, I recently did a sub-frame bolt on a W108 successfully.

So the factory bolt is a 12mm 1.5 thread.

I was going to start with a 10mm 1.5 tap, do I still need to tap it again to move up to the 12mm or can I just use a 10mm bolt?

Tried with the extractors and as everyone has said no good.

thx for all your help.

Nobody knows if I can tap this to a 10mm bolt or I HAVE to use the factory 12mm?

Basically you want to use the old bolt shell as your new threads? I think that part might work, but the bigger question is do you want a weaker bolt holding your subframe to the body. Is it easier than drilling out with 27/64 and tapping to 12mm?