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'90 200E
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Discussion Starter · #1 ·
Yes, the title is enough self explanatory I guess.

I've decided to clean the ground connections on my '90 200E this morning and the inevitable happened.

2703773


I don't think I will be able to get the nut off by myself today, but still I need to drive the car to a shop to get this off.

In the meantime, can I connect the battery ground to someplace else? Like the other nut that's just right on the shock tower? Or the other ground position? Although I don't think the secondary ground won't hold up with the current.


Have a good day folks.
 

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1992 CE 300-24
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423 Posts
You've somehow snapped the bolt head off,
likely by ham-fisted over-torque wrongly done.

However, since the remains appear to be still
projecting above flush, you should be able to
- carefully - cut a groove for a flat screwdriver
blade to engage, & undo it (in the proper way).
 

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'90 200E
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Discussion Starter · #3 ·
You've somehow snapped the bolt head off,
likely by ham-fisted over-torque wrongly done.

However, since the remains appear to be still
projecting above flush, you should be able to
- carefully - cut a groove for a flat screwdriver
blade to engage, & undo it (in the proper way).
Correct, it should've been snug all the way down by a shop prior.

Your method seems more reasonable than using a drill. Although I have a drill, the bits that I have don't look like they're up for the job.
I will try to undo it with a screwdriver, but how can I cut a groove on the bolt?

Thank you.
 

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1992 CE 300-24
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423 Posts
With a tiny disc cutter in a high speed unit,
or, slowly with a segment of hacksaw blade.

Or if you are accurate with a welder, a spot
weld of an extemporised handle like the
key to a corned beef can, or an old hex key.
 

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'90 200E
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Discussion Starter · #5 ·
With a tiny disc cutter in a high speed unit,
or, slowly with a segment of hacksaw blade.

Or if you are accurate with a welder, a spot
weld of an extemporised handle like the
key to a corned beef can, or an old hex key.
Thank you, I will surely try this.

Yet, the sudden realization hit me. I don't have any 13mm bolts lying around to put in after the removal of the broken one.

Can anybody give any advice on a secondary ground position?
 

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1992 CE 300-24
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423 Posts
Its the metric thread that matters,
not the head which the socket fits,
but you surely could 'borrow' one
from a less crucial location, somewhere
else on the car, in the meantime, no?

Either that, or find a Yamaha, they use
those 13mm bolt-washer combos, too.
 

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'90 200E
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Discussion Starter · #7 ·
2703785


Here's where things stand as of now.
I was able to move the broken bolt by a mere milimetres by chiseling it with a flathead screwdriver and a hammer, but nothing more.

I am considering hooking the battery cable to the other nut which holds two other grounds
from the car, but I am not sure whether it is safe to do so.

Would connecting all the grounds to a single nut fry my electronics? That's what I'm afraid of.
 

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'90 200E
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Discussion Starter · #8 ·
2703788


According to this schema, I will be connecting the grounds of W10 and W10/1 which are the battery and electronics (which is too broad of a term).

Again, would this be safe for a 15 minute drive to a shop which can get the bolt out properly?
 

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2014 G550, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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1,595 Posts
Just use the other stud for all three connections in the mean time. You may have to get a longer bolt to accommodate the extra thickness of three lugs, but until you get the other one out, it will work fine. Be sure to torque the bolt properly.
 

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1977 450 SEL 6.9
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868 Posts
You will likely need to drill and use "easy out". Use localized heat to heat the bolt remnants. Heating and cooling cycles usually gets the bolt to budge.
 

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1989 W124 260E
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3,436 Posts
Wow i thought you had broken the body around the earth point ,, I would have that out in the shake of a donkeys wetter ..Drill in a smaller hole and use extractor .A nice rewarding job in the end . Not life threatning ..
 

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You can ground anywhere you'd like on the Chassis. When I've broken grounds, I have set a rivnut and used a 13mm bolt as the new ground. You can also ground it to another point if you'd like. All you need is a tight connection to the metal. Unless you want it to be the way it was, in the same spot, etc.
 

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1989 W124 260E
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That might be possible if you can get to it , the whole thing is on an angle ..Stop pussy footing around and drill it out , job done ..Know what , this post on the broken bolts took 12 posts to find out whats needed to remove the bolt . A sim[ple way to do it is drill a hole small hole in the centre of said bolt smaller than the bolt itself . Then remove the wooden handle off an old file or rasp,then knock it in the pointed part of the file in to the hole in the bolt and turn it with a wrench .. Or drill a 1/16 hole in the broken part of the bolt on one side ,then use a pointed punch to tap it out ...I will pop back tomorow and give you more ways to do it ..
 

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2014 G550, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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1,595 Posts
I think that if you snapped the head off the bolt trying to remove it, there is probably significant corrosion on the exposed threads on the underside so threading it out it from the top may prove difficult. As suggested above, reach under and grab the protruding threads with pliers (or vice grip pliers) and see if you can turn it to remove. You might try turning it clockwise as viewed from the top to thread it out through the bottom.

That being said, there is no electrical reason why you just can't use the one remaining bolt for all three ground lugs. MB used two separate ones because it is good engineering practice to do so (maintenance, torque values between thin and thick lugs, etc.). If it were me and I couldn't thread the one bolt out with pliers, I would just use the one stud period. Big battery lug on the bottom, then the two smaller lugs, torque, then go have a beer and forget about it.
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,900 Posts
Yes, overthinking this. A ground is a ground.....grab one from another location that's close. You electronics don't care where the ground comes from as long as it's solid.

Kevin
 
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