300 SD stripped motor mount 8 mm bolt - Page 2 - PeachParts Mercedes-Benz Forum

Brian Carlton · #16 06-24-2007, 11:17 AM

Quote:

Originally Posted by dannyF

So, now I am down to using a bolt remover - a sort of left handed bit that drives into the bolt with a drill and, in my case, an extension. With the drill in reverse, it is supposed to unscrew the bolt. Has anybody tried this, particularly on the motor mount, and are there any voices of concern with this approach?

Unless someone has any other advice, I will plan to try this and I will report back.

In addition to the bolt remover, I can't stress the benefit of heat. Get that bolt warmed up very well with a propane torch. The bolt will lengthen when heated and the compressive force underneath the head will be reduced significantly. Spend the time to ensure that the entire bolt warms up........not just the head.........it doesn't need to get anywhere near red hot...........just 300-400 degrees will provide the relief that you need.

dannyF · #17 06-24-2007, 11:54 AM

Thanks for all of your replies. This is just the passenger bolt - the driver's one came out. Drilling it out is an option, particularly now that I have an extender for my drill. Sounds like that may be a better thing to try than the bolt extractor, to avoid the risk of getting the bolt extractor stuck.

Brian C., regarding your suggestion of heating the bolt - do you suggest I do that to facilitate bolt extraction, if I decide to try that? If I were to try drilling out the bolt instead, that probably wouldn't help, right?

Also, a friend suggested that I raise the engine (via the oil pan) to relieve some of the pressure on the motor mount and to facilitate the bolt's removal. I will be raising the engine after this step, anyway, but, I am not sure it will help in terms of bolt extraction, since the bolt is tightened in independent of the engine's weight. Any thoughts?

engatwork · #18 06-24-2007, 12:09 PM

Quote:

facilitate the bolt's removal

Raising the engine won't really help facilitate the removal unless it provides more clearance for the drill.

Brian Carlton · #19 06-24-2007, 01:01 PM

Quote:

Originally Posted by dannyF

Brian C., regarding your suggestion of heating the bolt - do you suggest I do that to facilitate bolt extraction, if I decide to try that? If I were to try drilling out the bolt instead, that probably wouldn't help, right?

Also, a friend suggested that I raise the engine (via the oil pan) to relieve some of the pressure on the motor mount and to facilitate the bolt's removal. I will be raising the engine after this step, anyway, but, I am not sure it will help in terms of bolt extraction, since the bolt is tightened in independent of the engine's weight. Any thoughts?

Yes, heat will facilitate extraction. It won't benefit you if you choose to drill.

Raising the engine won't do anything to relieve the tension in the bolt threads and the friction under the head of the bolt. You are correct.

dannyF · #20 06-24-2007, 06:29 PM

Well...

I tried heating the bolt, probably unsuccessfully. My torch would go out if I put it too far through the orifice, so I had to hold it back a ways from the opening to the engine mount bolt. Questionable whether the flame actually heated the bolt (which is recessed way up there). Anyway, then I tried using the bolt extractor. It did grind into the bolt, but after I created the hole and tried to use the bolt extractor in 'reverse drill mode', it got stuck to the point that the bit extender from my drill lost hold. So, now I have a stripped bolt with the bolt extractor stuck in it, sort of as Sexto stated happened, too. No way to grab that bolt extractor

.

Is it possible to drill it out in this case (I assume I need a reverse threaded drill), or must I resort to trying to remove the arm? If the latter, I assume there is a thread on that in this forum?

Thanks...

Dan

jbaj007 · #21 06-24-2007, 06:41 PM

Hi Dan,
Sorry to hear about the mount screw woes. Can you get a socket on an extension up to the extractor. I'm assuming the extractor is just stuck, not broken? If it's not "grabable", I'd go for arm removal. I've seen a guy drill a small hole in the arm, from the top (it was driver's side, though) and shoot PB Blaster from the top.
I've also seen a fellow drill out the whole internal hex screw top to bottom, through the arm and replace it with a high grade# nut and bolt.

dannyF · #22 06-24-2007, 06:45 PM

Hi Bruce!

No, the extractor is not broken, but its threads may be stripped (I tried hard to get it out with the drill...). I can see if I can find a small-enough socket that may accomodate it.

Dan

dannyF · #23 06-24-2007, 10:41 PM

Thanks, Bruce. Your suggestion worked and the extractor bolt is now out! I used a 3/16 socket on an extension and it grabbed hold. I was tempted to try to unscrew the bolt that way, but I think I would have been tempting fate. So, now I am where I was before, maybe a little wiser, maybe not.

Anyway, my plan is to now drill the bolt out, but I have some questions along those lines.

1) I assume I need a left-handed drill bit?

2) Does drilling out a bolt remove the whole bolt, or just the head?

3) If the whole bolt isn't removed, won't I still need to pull the arm off, or do I just drill with a larger and larger bit untilt he whole thing's out?

Clearly, I have never drilled a bolt out before...

jbaj007 · #24 06-24-2007, 11:12 PM

I think that the internal hex on that machine screw (everybody calls it a bolt, but there's no nut, so....) is 8mm. right? The diam. of the screw shaft is 10mm., I think. If you used a 10mm. bit, you would drill off the head; if you used smaller bits you would drill though it. Ever increasingly greater diameter bits woud eventually leave you with a "shell" of the screw shaft that often kinda "flicks" out counterclockwise.

Sears has left-hande bits, just as you surmised. Some people have had the screw come out while using them. Serendipitous!

If it doesn't come out cleanly, then removal of the arm would be best to set a helicoil type insert.

dannyF · #25 07-02-2008, 12:21 AM

Well,

Its a year later. Last year I ended up putting the one 10 mm engine mount screw that I was able to get out back in and driving my car with it that way, since I didn't have time to work on it anymore and it was still recoverable. Now I figured it was time to complete the job... So, I finally managed to drill out the 10 mm screw head. From other posts I saw, I realized it would have been better just to try to remove the head by drilling, but I drilled into the screw, too, and eventually I got the head out. Upon loosening the shocks and raising the engine with my jack, I removed the passenger engine mount to see part of the screw remaining inside the shaft... While loose, it won't come out, probably indicating that I managed to ding up the threads. This is confirmed when I look at the old mount - my drill made its way to the edge. So, I need to come up with another fix here...

One issue is that directly above this bodged screw (on top of the shaft) there is 17 mm hex head bolt that seems to be pressing some support piece of the engine into the motor mount. Does anyone know what this bolt is? In order to re-mount this engine mount, because I think I messed up the threads for the 10 mm support screw, I will likely have to remove this bolt and find a long bolt that I can push all the way through from the bottom (once I remove the broken screw by drilling it out...).

What a mess I've created... Any suggestions are welcome. Thank you!

dannyF · #26 07-02-2008, 12:46 PM

I realize that I used the wrong terms in my last message - I butchered the alloy arm above the engine mount in the previous note. A 'bodge' would be a fix, which is what I don't have yet....

My 'bodge' would be to drill out the alloy arm and place a nut at the top. However, there already seems to be a 17 mm hex head at that point. Can someone tell me why there is a 17 mm hex head bolt at the top of the alloy mounting frame that is above the engine mount on the passenger side of my 84 300 SD? I wil try to remove it - it is tight but I sprayed it yesterday with penetrating oil.

dannyF · #27 07-02-2008, 02:48 PM

I just called the dealer. Apparently, the 17 mm bolt on top of the engine mount support on the passenger side is merely holding the battery cable. So, I feel better about removing it and drilling through to support a longer bolt coming up from the engine mount with a nut on top. Any thoughts or has anyone done this?

turbobenz · #28 07-02-2008, 04:48 PM

just remove the two 5mm allen bolts that hold the engine mount to the car.

Chad300tdt · #29 07-02-2008, 04:54 PM

Quote:

Originally Posted by dannyF

I just called the dealer. Apparently, the 17 mm bolt on top of the engine mount support on the passenger side is merely holding the battery cable. So, I feel better about removing it and drilling through to support a longer bolt coming up from the engine mount with a nut on top. Any thoughts or has anyone done this?

On the w123's the battery cable isn't hooked to the mount arm like you're describing. I'm sure it will be fine if you reattach it with a long bolt and nut after you drill through the arm. I was going to drill through the arm and use a long bolt and nut as a last resort myself, but was able to dodge that bullet.

dannyF · #30 07-04-2008, 03:53 AM

Well, both engine mounts are out now and I am trying to remove the passenger-side engine mount arm to re-drill the hole.

Question: How many nuts support this arm? Thus far I have removed 4 17 mm nuts, but the arm, though loose, still doesn't seem to want to come out. There is a piece just above it that I cannot tell if it is a part of, but it has a 10 mm bolt and a 17 mm nut (I think) above it. Do I need to remove these as well? I just can't tell. I'll look at it again tomorrow if I can.