Stripped socket cap bold (motor mount) help? - PeachParts Mercedes-Benz Forum

networkboy · #1 05-02-2007, 09:01 PM

Hey all,
My MB has been sidelined for three months with a fully borked motor mount and tranny mount waiting for me to get a free weekend to fix them. Well last Saturday I finally had some free time, so...

One heft with the breaker bar later the first of the 10mm bolts on the underside was toast. So, any suggestions? or should I bite the bullet and pay the indy to do the job? can I make it more expensive for myself if I trash the head of that bolt any worse?

In any case I have stainless replacements for all 6 socket cap bolts for the motor mounts, so this should not be a problem again

-nB

t walgamuth · #2 05-02-2007, 09:23 PM

you can drill them out.

probably stripped the cap because you didnt get the allen seated fully. always clean the socket out good so you get the full depth. then you will never strip it.

also some folks drive in a torqx or a bigger allen.

good luck

tom w

networkboy · #3 05-02-2007, 10:23 PM

I cleaned it out well, it was fully seated (as best I can upside down at least).
I heard someone mention banging in an oversized torx. Think that'll work? I'm afraid if I muck it up more I'll make the effort of removal that much harder, thus more expensive. If I drill it out and it's still that tight how on earth do you get the stud out?
Also, should I invest in an impact wrench for the rest of them?
-nB

t walgamuth · #4 05-02-2007, 10:56 PM

the torx has worked for others, i believe. i have not tried that myself. if you cannot get the bolt out and you drill it you can possibly clean the threads out and insert a new bolt or you can drill the threads out an install a thru bolt.

good luck

tom w

dkveuro · #5 05-02-2007, 11:17 PM

Cheaper to buy a 12mm drill with a long shank.

.

TMAllison · #6 05-03-2007, 12:10 AM

If pounding a torx bit in buggered it up more, couldn't he still weld a nut to the head of the cap bolt and try again before having to drill it out?

networkboy · #7 05-03-2007, 12:51 AM

If you could get in there to weld...
Might be worth a shot though (somewhere around here I have an arc welder that belonged to my grandfather in-law).
-nB

t walgamuth · #8 05-03-2007, 05:33 AM

just dont set the car on fire!

tom w

WINGAS · #9 05-03-2007, 08:08 AM

I cant picture the location of the bolts, but I had a similar problem with a shifter mount on a Richmond road race 5 sp that I used red loctitie on. Bad move. The allen head got buggered, so heat ( and in your case Thrust or PB Blaster) and driving in an oversized torx worked. My back up was to grind a slot int he head using a disc in my Dremel tool to fit a screwdriver snug. 3rd backup - drill it out enough for an Ez-out.

Drilling on grade 8 fasteners isnt a cake walk. I avoid it if I can.

Shawn D. · #10 05-03-2007, 08:44 AM

Quote:

Originally Posted by networkboy

In any case I have stainless replacements for all 6 socket cap bolts for the motor mounts, so this should not be a problem again

Don't be so sure of that -- unless you got graded stainless, it's likely to be weaker than a Class 8.8 (~Grade 5). For this application, I'd use a Class 10.9 (~Grade 8).

dkveuro · #11 05-03-2007, 09:16 AM

Drill off the head...lift engine and remove mount from block.
Being as the socket head of bolt is inside the member, there is no room to weld or grind.

.

WINGAS · #12 05-03-2007, 10:24 AM

Yes, then cutting it off is a viable alternative.

rrgrassi · #13 05-03-2007, 10:42 AM

I had the same issue on the passenger side one. I ended up pounding in a larger allen. All the pounding broke the grip that was on the threads and the bolt came right out. I got new ones at stealership.

Mustang_man298 · #14 05-03-2007, 11:28 AM

Quote:

Originally Posted by Shawn D.

Don't be so sure of that -- unless you got graded stainless, it's likely to be weaker than a Class 8.8 (~Grade 5). For this application, I'd use a Class 10.9 (~Grade 8).

I agree, stainless is much softer than grade 5 hardware, just look at torqueing specs-how much lower they are on stainless. That aside, if you did use it, you would still need to use anti seize, as stainless LOVES to burr up and bind on the slightest whim, and a little corrosion in that bolt hole would be all it would need....and you don't even want to get into trying to drill on stainless.....

A few years ago I bought a set of easy outs from the MAC truck, price wasn't too bad and they are absolutely wonderful, I've twisted many stripped cap bolts out of my MB's with no drilling, and the low profile makes them great in tight places. (screw extractor set # 25SE)

automch · #15 05-03-2007, 11:31 AM

I have had this happen many times and always been able to remove the bolts without drilling or using a torch! Take a very large drift and hammer the allen head of the bolt several times. This will do 2 things; 1, the sharp smack will help jar any rust loose, and 2, it will mushroom the head slightly. Then drive the allen socket into the bolt, Be sure the allen socket is fully seated. Then "Tighten" the bolt slightly. Yes I said tighten it, then loosen it and it will come out. Again only tighten it enough for it to move as little as possible. This technique has worked for me many times on these allen headed bolts. It also works well to slightly tighten brake bleeder screws before loosening them.