W124 severe pothole damage - PeachParts Mercedes-Benz Forum

cmcdonnell · #1 07-08-2015, 10:16 PM

I was cruising along at about 30 mph and I hit the deepest pothole I have ever seen. Right front tire and wheel are toast. Maybe even the ball joint, which is no easy job on a 400E since it is welded to the lower control arm. About a day later, I noticed some clanging sounds in the right rear. Sure enough, my rear subframe is broken. I got the damn thing off today, but the front left bolt snapped off and is stuck up in the chassis. Does anybody have any experience removing said bolt. If I can get it out, I can save my beloved Benz. Disclaimer: the subframe must have been weakened by rust to break like that, but being under the car as often as I am, I just didn't see it.

BatteredBenz · #2 07-08-2015, 11:53 PM

That bolt has a long section of threading, the threading is quite fine, and there is plenty of blue threadlock on it. So heat will help. Welding a nut on any remaining bolt shank would probably be best. If there isn't any shank drilling ith progressively larger left hand thread cobalt drills is probably the next best method. The whole experience will get worse before it gets better, unfortunately.

cmcdonnell · #3 07-09-2015, 12:22 AM

Thanks for your help. I am watching youtube videos on bolt extraction right now. Is cobalt the strongest for hardened steel bolts? Oh, and there is no thread left exposed.
Well, at least I got the subframe down today.

BatteredBenz · #4 07-09-2015, 12:58 AM

The bolt broke when you where wrenching it not as a result of the pot hole damage? Assuming so, that means the bond between the treading is going to make it difficult. Without something to weld to that's out.

The process would be to start drilling with a small bit as perfectly centered as possible, keeping the hole centered drill it successively larger, depending on the diameter of the bolt you'll want to get the hole large enough to tap and take the largest left hand thread bolt you can. Get it drilled, then get it tapped, run the bolt into the hole you tapped so you know it will go and how far it will go. Get some fire or heat on the drilled broken bolt, I think the chassis is a tubular threaded post, right? Get some heat on that as well. let it soak a minute and then thread the bolt in run it home and hopefully the heat will have helped brake the bonded threading and with the left hand thread bolt you'll be able to apply enough torque it beck it out. It will cool and tighten up so you might need to apply some heat as you coax it out.

If you can rig some sort of device to center the drilling that would be good, if not start with an automatic center punch, that will allow you to get as close to center as possible, then you can make a good centered mark deeper with a pointed punch and hammer. Try to keep the drill bit as straight and square as possible, use some lube, tapping fluid or wd40 to help the cutting. If you can get to a real hardware store or maybe online look for good drills, American made, expect to pay at least a couple buck each for them, you'll probably need to go online to find a correct left hand bolt and tap. Using any type of EZ-Out is a last resort, Id rather deconstruct the bolt from the inside and pick the threads out rather than take the risk of breaking off a hardened steel tool tip down in the hole(or up in the hole in your case!) Your probably going to need the correct tap for that bolt's threading to chase it before you try to thread a new bolt into place anyway so you probably should start chasing that down too. If you don't between the threadlock and any thread damage you might not be able to get the bolt fully snugged into place. Good luck

I saw this happen to someone else doing this work where they got under the car and being in an upside down orientation they tried to bust the bolt loose in the wrong direction and it just tightened a bit and snapped off when they put their muscle to it.

Chinese "cobalt "drills would be better than the average drill bit, but when they can't grind them straight and precise hardening them will only make them easier to break when they get used.

cmcdonnell · #5 07-09-2015, 01:35 AM

Yes, I tried a few times with my combination wrench, but it woudn't budge. But I was turning in the correct direction. Then I hit it with my impact wrench and it snapped right off. Thanks for all the information. I feel more hopeful now. American made-not Harbor Freight I guess.

Stretch · #6 07-09-2015, 01:51 AM

I was wondering if the front left bolt inner side was accessible under the rear seat or not. A bit of decent penetrating oil "top down" might help.

BatteredBenz · #7 07-09-2015, 02:20 AM

No I don't think you can at least not easily, the front attachment points are incorporated into the sort of frame rail inside and under at least one layer of sheet metal when coming from the top. And properly so when you think about the stresses that can be brought to bear on the structural attachment points like that.

Stretch · #8 07-09-2015, 04:55 AM

Quote:

Originally Posted by BatteredBenz

No I don't think you can at least not easily, the front attachment points are incorporated into the sort of frame rail inside and under at least one layer of sheet metal when coming from the top. And properly so when you think about the stresses that can be brought to bear on the structural attachment points like that.

I've never been so intimate with a W124! But I've crabbled about with my W201 and the design is similar - but even so I also can not remember for sure if the upper side of those nuts are accessible. They are most certainly not accessible on my W123 - perhaps "the trend" did continue...

...I have to fit a new rear ABS sensor on my car soon so the back seat will be out - perhaps I'll have a better insight into this construction then.

Stretch · #9 07-09-2015, 05:22 AM

Scrub that - a quick look on the EPC images on a certain MB website shows a very different rear structure on the W124 - much more like the W123 than the W201 as far as I can make out. I still couldn't identify the positions of the subframe mounts in the images I saw - perhaps it is worthwhile remove the rear seat for a quick peek?

radunegru · #10 07-10-2015, 02:44 PM

You have to also check the front spring perch. I had a similar event with my 1993 300E few years back. Tire and wheel destroyed plus spring perch got detached from the body on about half of the welding surface. Just about enough for spring to pop, but caught in time. Got it professionally welded and repainted.

cmcdonnell · #11 08-05-2015, 01:03 PM

Spring perches are in good shape. I completely rebuilt the front end last year with all new parts, except the knuckles are original.
I bought a set of IRWIN left handed cobalt drill bits with coresponding bolt extractors. The drill bits cut like butter but the extractors have not been very useful. Now there is a very thin wall of the old bolt stuck to the threads of the hole and it will not budge! Bi-metal fusion? I have to admit that my drill hole is a little off-center but does not seem to be touching the fitting in the body. Ordered a new (donor) subframe last night from Alabama with an alleged 110K on it. Hoping it has never seen salty roads!

Chris W. · #12 08-05-2015, 07:56 PM

Can you run a tap in there to chase out the remnants?

And kudos to you for cranking on the big job of dropping the subframe so quickly! That would have taken me a week or two of short duration attacks, at best!

Rgds,
Chris W.
'95 E300D, 447K

BatteredBenz · #13 08-05-2015, 08:28 PM

Not to be negative but the "extractors" are really more likely to break off than they are to extract in many cases, unfortunately!

You can try but you need to be careful, if you break the extractor tip off it's hardened and can be almost impossible to get out except by EDMing it! But if you've got a hole big enough for the largest extractor you can fit in there I would try heating the hole drilled into the bolt, this will get the bolt hot enough to soften up the blue threadlock that those bolts are coated with at the factory. Just too hot to touch around 150F softens the blue stuff. Get it hot, place the easy-out which has some sort of good handle you can keep square and straight into the hole even give it a couple short sharp raps with a hammer to get its flutes to dig in a bit and apply the twisting force while pushing upwards to help the "bite", it might be enough to overcome what's holding it together now. The thing with the easy-outs is the are hardened but the down side of that is they are more brittle as well. If you accidently or inadvertently cock them off to the side they will usually break right where they don't have the support of the drilled hole around them.

If it were me I would get a good hole and then get a left hand tap and a left hand bolt that will fit the hole you've drilled, the tap and the bolt will be slightly larger than the hole. carefully tap the hole in the bolt, you don't want to break the tap off in there so use plenty of lube, Tap-Ese, or any spray lube like WD40 or PB Blaster will help the tap from chattering and prevent it from having problems. Then run the bolt up into the hole to make sure you can accomplish that easily without any problem, break out the torch and heat the drilled and tapped stuck bolt, again just enough to soften the threadlock, then with your ratchet or wrench handy, thread the left-handed thread bolt into the left-handed tread hole you created and tapped, then carefully and mindfully apply the torque to that bolt and hopefully between a solid turning and the softening of the threadlock the broken off bolt will start turning out. You can try the heat/ turning cycle a couple times if you don't get any results the first time, just try to be careful and not break things making it worse!

If you can't get it out that way, drilling the hole successively larger, essentially hollowing it out seems like one of the only strategies left. You can do some damage to the original threading that way but once the bolt parts are removed you can run a tap through them and most likely maintain enough "beef" to hold the new bolt. I'm sure the exact dimension of that bolt and its threading but it's pretty good size and has quite fine threads so you might have to hunt up a tap for that online rather than at the Home Depot. One of the tool and machining online retailers like MCS, ENCO, McMaster-Carr are probably the best sources for a tap like that.

You got yourself a real challenge good luck with it, your going to need that and a lot of perseverance!

gear-head · #14 08-05-2015, 10:53 PM

No doubt, a real serious challenge! I sure don't envy you! Rather admire you for taking on this challenge! I'm wondering about that approach of successive drilling of increased size bits, removing the reminder of broken bolt, then maybe instead of being too concerned with having enough of the original threads remaining, just plan on drilling it out completely to the correct size to tap it and run either a "Time - (Ok, this damn Apple won't let me spell it the rite way!). It is called a "time" - followed by the letters "s", "e", "r", "t" or you may prefer to use a Helicoil. Just my two cents, not to conflict with or contradict any of the great advice previously given you. Of course the way I'm suggesting does hinge on whether or not there's adequate material there to drill it large enough and tap it. Best of luck and will be looking forward to reading about your progress and success!

cmcdonnell · #15 08-06-2015, 12:13 AM

Thanks again for the helpful replies-I will try all of the above. I am obsessed now, and I WILL get this done. Just a note that since I was drilling upside down I used MB wheel bearing grease for the lube and it worked out quite well. It stayed on the bolt and the drill bit and contained all of the shavings while drilling and didn't drip all over the drill and me. Tomorrow morning I will go back at it.