How to remove broken bolt? - PeachParts Mercedes-Benz Forum

carman850 · #1 02-25-2004, 09:18 PM

When I was replacing rear sway bar bushings, I broke one of the hex bolts that hold bushing brace, the thread was completely rusted, so I used too much force, ended up breaking the hex head, the thread seized in the bolt which is part of the bracket, the bracket is welded to the frame.

Is there any trick to remove the remove the bolt, drill it? I don't have much experience dealing with steel, would normal drill bit be able to handle Mercedez steel? I now use a C-clamp holding the brace so I can still drive it temporarily.

bjcsc · #2 02-25-2004, 09:36 PM

Can you post a picture? It would help in giving you advice on how to fix it.

BF_JC230 · #3 02-25-2004, 10:10 PM

when i first got my 1980 w123 230 sedan - i was doing basic maintance and broke off one caliper bolt in the front. (i did not mean to, it happened)

yes i drilled it out. - it was too rusted in from no locktite or neverseize being used - could not use a bolt out bit (a reverse cut drill bit) or other basic trick.

found center, center punched, pilot drill, and worked up to size, rethreaded and cut out the old thread as tapped new threads at the same time all together...

people beleive in helix coils and such - each to their own.
Jake

carman850 · #4 02-25-2004, 10:32 PM

Sorry, modified my original post, it was actually "Sway bar bushings" not "control arm bushings" and I don't have a digital camera.

Thanks, I will give it a try tomorrow.

chazola · #5 02-26-2004, 11:35 AM

I had the same thing happen on my 300e last week.

I tried to drill it out and so did my tech, but in the end he sawed the old 'nut' part off and put in a new 'real' nut. most expensive bolt I've ever broken...

carman850 · #6 02-26-2004, 06:27 PM

I know someone must have experienced it, that bolt looked pretty sturdy, 13mm I think, but I easily broke it with a 3/8 ratchet.

I tried to drill it, but the drill bit wouldn't bite at all, chazola, how did your tech saw the nut off? the nut is in the mounting bracket, there is little room to fit in a saw.

With a C-clamp holding the rear sway bar bushing bracket, I didn't feel much difference when driving , guess there isn't much force on that part.

chazola · #7 02-26-2004, 07:08 PM

did the inner (towards the front of the car) bolt break or the outer?
Mine was the outer one and i don't know if that made a difference to the ease of getting a saw in there. He did it somehow- that's as far as I know I'm afraid.

My tech said that part being broken wouldn't really effect the the 'feel' all that much, but would cause other suspension parts to wear quicker. There is quite a lot of tension in the bar I believe so I think a proper repair is the way to go. Even if it did cost $120.

grrrr...that'll teach me to DIY!

kip Foss · #8 02-27-2004, 12:57 AM

A few suggestions from 45 years of mechanicing.

Before attempting a bolt-any bolt- hit the head a few times with a hammer fairly hard. This sends a shock through the bolt that will help break the rust bold.

Don't tear into the bolt with all your might. If it doesn't come by un-screwing, try tightening just a bit. A couple of hits with the hammer, some oil, a few wiggles, etc.

If the bolt shears off and you have room try drilling it out. There are reverse drills but usually if the bolt is that frozen the chances are good that the reverse drill won't aid in backing the bolt out.

One problem with using 'Easy outs' , etc., is that they are just marginally stronger than the bolt. If you twist one off in the bolt (which you can easily do) you are really a screwed goose. They are too hard to drill out and usually have to be taken out with a spark eroder. A very costly operation.

Drilling the bolt out to the originally tap size and re-tapping the hole presents a problem. What you have now is a hole with a rusted spiral down it with vertually no good metal left in which to make threads. Also, the chances of you getting a tap to cut out just the original threads is virtually nill.

Spend $10 and get a 'Heli Coil' of similar thread renewal kit. I use Heli Coils up to 30 mm dia. where I work and basically have had no trouble with them. Take it easy drilling. Get into a comfortable position. Keep a steady pressure on the drill. Don't feed too hard or when the bit breaks you are just as screwed as if it had been a tap. Know how deep you bolt goes and don't over drill. Use a lubricant like 'Tap Magic" It is great stuff.

When you tap don't do it all at once. Get the tap started a few turns and then back it up a turn. Run it in a turn or so and back it up a half turn. Back the tap all the way out every 5 turns or so to clean off the shavings. When the tap feels like it has hit the bottom of the hole it probably has so don't force it. See the above about broken taps.

Be sure that when you start the tap that you get it square to the hole. A little bit off at the start makes for an uncorrectable problem in about 5 turns. Before you start tapping, go to a tool company and get a 'tap handle'. It is a little 'T' shaped device that holds the tap and makes it much easier to get square than trying to use a wrench. There are 2 sizes. Take your tap with you so that you get the right size.

Another trick is to weld a bolt to the head of the frozen one. If you can get to the bolt and if you have someone that is a good welder this way will often work. After welding let the bolt cool to the touch. This will often shrink the bolt enough to make it easy to back out.

Before you start any of the above it is often handy to find an old mechanic or machinist and ask then what they suggest. Not only do they have a wealth of experience but they would be flattered to have someone ask them for help. They might even help you after hours for nothing. If they do help you I am sure that they would not turn down a $20 bill when the job is finished.

Good luck.

neileg · #9 02-27-2004, 08:49 AM

Quote:

I tried to drill it, but the drill bit wouldn't bite at all

Buy a new drill bit, smaller than the bolt, say 1/8" or 3mm. Get a cobalt bit if you can since these handle hard materials better than normal HSS bits. If you try and start with a drill that is too big, i.e. near the size of the bolt, you won't get that bite.

If there is any of the bolt shank protruding, a variation on Kip's tip is to weld a nut onto the shank. If you use a MIG and fill up the hole in the nut, this can be a very good joint. Plus, the heat involved will help break the rust hold, just like Kip says.

stevebfl · #10 02-27-2004, 09:10 AM

What a good bit of advice, Kip.

Saves me from saying all that, especially the part about getting the old threads back!

carman850 · #11 02-27-2004, 10:12 AM

Kip et al.

With all the advices given, I am pretty confident that I can have the job done over the weekend, much appreciated.