Damaged Engine Mount Bolts 123, 126, 201 - PeachParts Mercedes-Benz Forum

whunter · #1 02-17-2009, 01:06 PM

I can not STRESS this enough..

If the engine mount bolts are even slightly damaged, REPLACE them, don't put bad ones back in...

Item Number: 914019008000
Main Category: Mercedes Benz
Sub Category: Engine Mechanical
Description: Bolt...engine mount to subframe...Application...Chassis: 100, 107, 108, 109, 110, 111, 113, 114, 115, 116, 123, 126, 332, 684
Weight: 0.050

Item Number: 1239900212
Main Category: Mercedes Benz
Sub Category: Engine Mechanical
Description: Bolt...engine mount to engine support bracket...Application...Chassis: 123, 126, 201
Weight: 0.150

NOTE – All prices on special order parts subject to change without notice.

Have a great day.

JonL · #2 02-17-2009, 01:57 PM

Why?

rrgrassi · #3 02-17-2009, 02:32 PM

Because next time, they may not come out.

Diesel911 · #4 02-17-2009, 11:02 PM

If that thread concerning the life of new Motor Mounts to be only 2-3 years is true; it makes sense to get rid of the damaged ones as you may be replacing the mounts in a few years.

JonL · #5 02-17-2009, 11:27 PM

I'm still not clear... what is the issue? rounding out of the hex? Thread galling and seizing in the mount? Should the threads get cleaned up with a die before reinstalling? Anti-seize? Loctite? I just replaced my mounts... didn't notice anything unusual with the bolts.

bgkast · #6 02-17-2009, 11:29 PM

The hex is easy to round out because dirt and grease gets in the hex hole and does not allow the allen bit to seat properly. My passenger mount's bolt is almost totally rounded out right now. The mount was not bad so I stopped trying to replace it for now...

IndianaJo · #7 02-19-2009, 07:45 AM

I replaced the short allen head motor mount to frame bolts buried in the frame with 120 mm long bolts capturing a rubber cushion and washer under the frame. Biggest reason, I have spent a lot of time grinding off/drilling out stripped allen bolts at work, and buried in the frame like they are, original bolts would be inaccessible to a die grinder to cut them off. Also, since manual car doesn't have shock absorber mounts, a little additional rubber vibration isolation is a good thing. To buy these bolt one at a time cheaply, buy "gm starter bolt" from dorman "help" line. Of course, boxes of bolts are cheaper by the each. I've got some 1" thick x 6" wide rubber belting I use to make engine and transmission mounts, use a spade drill to drill holes in it.

JonL · #8 02-19-2009, 08:56 PM

OK, how about this... if the hex rounds out, get a drill bit just larger than the shank of the bolt. The rounded hex will be a nice pilot for the drill. Drill until ye olde bolt head falls off. Lift mount off subframe. No?

JimmyL · #9 02-19-2009, 09:02 PM

Quote:

Originally Posted by JonL

OK, how about this... if the hex rounds out, get a drill bit just larger than the shank of the bolt. The rounded hex will be a nice pilot for the drill. Drill until ye olde bolt head falls off. Lift mount off subframe. No?

OK, then what??

You still have an aluminum engine mount arm that needs a threaded hole for the next engine mount....

JonL · #10 02-19-2009, 11:58 PM

I hope I'm not a simpleton, maybe I am. I replaced my mounts about two weeks ago. I think I remember that all the threaded holes are in the mount. The aluminum bracket and the subframe (permanent part of the chassis in the W201) are both clearance holes. It's a W201 190D. Am I missing something?

If I'm wrong and there are threaded holes that get buggered up in more permanent parts, helicoils to the rescue.

Really, I'm struggling to understand why these bolts are considered to be a big deal.

vwnate1 · #11 02-20-2009, 12:03 AM

And you're correct , simply drill the head off the bolt then remove the aluminum, bracket and unscrew the old bolt .

This is routine service on collage kids cars after they screw it all up .

whunter · #12 02-20-2009, 02:04 AM

Quote:

Originally Posted by JonL

I hope I'm not a simpleton, maybe I am. I replaced my mounts about two weeks ago. I think I remember that all the threaded holes are in the mount. The aluminum bracket and the sub-frame (permanent part of the chassis in the W201) are both clearance holes. It's a W201 190D. Am I missing something?

If I'm wrong and there are threaded holes that get buggered up in more permanent parts, Heli-Coil® to the rescue.

Really, I'm struggling to understand why these bolts are considered to be a big deal.

Your logic appears to be:
* Damaged parts should be re-used until they totally fail, requiring additional time, money, and/or energy to repair.

Sorry, that defies both Logic and Common Sense..

Engine mounts are safety = Heli-Coil® repair should be the LAST resort, it can fail the wrong way during a traffic impact, possibly killing you or others...

Example of repair:
W123 and W126 engine mount

If the two small upper Allen cap screws are damaged/rounded, the mount will NOT come off the frame!!!

If the large lower Allen cap screw is damaged/rounded, the engine will not separate from the mount!!!

If the inner upper and the lower cap screw are damaged:
* You must raise and support the vehicle high enough for drill access underneath
* Drill the head off the lower bolt
* Raise and support the engine
* Drill, saw, or grind out the upper bolt head, (any V8 is seriously difficult to access)
* Remove the mount
* Extract the threaded stubs
* Replace the engine mount
* Replace the destroyed cap screws with NEW

This repair could have been avoided by replacing six damaged fasteners..

Here is a short list of some vehicles using these mount bolts.

W123
280TE W123.000 M110.000
200, 230, 230E W123.023 M115.954
280E W123.033 M110.984
230C, 230CE, 280CE W123.053 M110.984
200D, 220D, 240D W123.123 OM616.912 I4
300D W123.130 OM617.912 I5
300D-T W123.133 OM617.952 I5
300CD Coupe W123.150 OM617.912
300CD W123.153 OM617.952 OM617.912
300TD W123.190 OM617.912
300TD W123.193 OM617.952 OM617.912
230E W123.223 M102.I4
200T, 230TE, W123.283 M102.000

W126
280SE W126.000
300SE W126.024 M103.981 I6
300SEL W126.025 M103.981 I6
380SE W126.032 M116.961/963 V8
380SEL W126.033 M116.961/963 V8
420SEL W126.035 M116.965 V8
500SEL W126.037 M116.963 V8
560SEL W126.039 M117.968 V8
380SEC cpe W126.043 M116.963 V8
500SEC cpe W126.044 M117.963 V8
560SEC cpe W126.045 M117.968 V8
300SD W126.120 OM617.951 I5
300SDL W126.125 OM603.961 I6
350SD W126.134 OM603.970 I6

whunter · #13 02-20-2009, 02:19 AM

Quote:

Originally Posted by vwnate1

And you're correct , simply drill the head off the bolt then remove the aluminum, bracket and unscrew the old bolt .

This is routine service on collage kids cars after they screw it all up .

The W201 engine mount is generally simpler to replace than a W123 or 126.

Yes, this is routine service, because so many damaged cap screws are used again, any service garage loves this work = $$$.$$ in their account.

It is penny wise and dollar foolish, when the repair could have been avoided by replacing damaged fasteners before installing the new mount..

cmbdiesel · #14 02-20-2009, 10:05 AM

In my world, any damaged bolt gets replaced.
Did a head gasket when I was in high school, and reused the bolts because the dealer wanted 5 bucks apiece for them!!! First one to get torqued broke.
Thankfully, there was enough left to get ahold of with a vice-grip when I removed the head again, but didn't have to be that way. Lesson learned, and the guy at the parts counter was laughing when I came back for the bolts I had just refused 3 hours before.
Best time to replace something that is worn out, is when it's already removed.
One easy out for a rounded out allen head is to weld a bolt right onto the end of it so you can get a wrench on it.

JonL · #15 02-20-2009, 03:34 PM

Quote:

Originally Posted by whunter

Your logic appears to be:
* Damaged parts should be re-used until they totally fail, requiring additional time, money, and/or energy to repair.

Sorry, that defies both Logic and Common Sense..

Nah, not at all what I'm saying. Let me clarify. First of all, on my W201 with hydraulic mounts, there would be really no difficulty in removing any of the fasteners should there be a problem. I now realize that this is not the case with the other type of mounts and on other cars.

Second, the original post I read as being rather alarmist, as if the concern was similar to that of reusing stretched head bolts. I asked why, because with my recent experience I couldn't see any cause for such concern. Now I understand.

Third, I'm quite experienced with fasteners as both a former mechanic and a current mechanical engineer. I wouldn't reuse any component that I deemed to be damaged in way that would meaningfully affect its serviceability. But that doesn't mean that I discard every fastener simply because it might be a little beat up. It's always a judgement call, and I feel quite comfortable with my ability to make the judgement for myself. The original post made me think there was more to the story than there is. Thanks for the clarification.