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1973 w114 280, m110 engine
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448 Posts
Discussion Starter #1
So my subframe mounts stopped existing and it's time to replace them.

Most write-up recommend to drop one side at a time. Since it's with m110 engine - rather biggish in comparison to other engines - i wonder if it wouldn't be "easier to unbolt the engine from mounts and shock dampeners and drop JUST the subframe?
 

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'71 250C, '99 SL500
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132 Posts
In my opinion, NO. Based on my experience with my M130 250C and motor mounts on an R129 it is much easier to do one side at a time. There is a lot less work to get the bolt hole lined up because nothing is going to shift sideways. Trust me, do one side at a time. Just my opinion.
 

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'72 250C, '74 280C, '85 500SEL, '81 300CD.
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1,006 Posts
Take SNEBCB's advice. Unless you have a cradle to hold the engine in place you are never going to get the engine mounts lined up. I have a cradle and I STILL only do one side at a time. Just follow the instructions I posted elsewhere and you'll be fine.
 

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1973 w114 280, m110 engine
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448 Posts
Discussion Starter #4
Take SNEBCB's advice. Unless you have a cradle to hold the engine in place you are never going to get the engine mounts lined up. I have a cradle and I STILL only do one side at a time. Just follow the instructions I posted elsewhere and you'll be fine.
In one of your write up you've done complete subframe rebuild, did you also do mounts replacement with subframe still on the car? If so i have so many questions....!
 

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'72 250C, '74 280C, '85 500SEL, '81 300CD.
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1,006 Posts
Mount replacement is pretty straight forward. Two Allen head bolts (6MM Allen wrench) going into the cross member and one large (could be either Allen or hex head) going through the engine support into the mount.

The key is to get those Allen heads CLEAN before you even attempt to remove them. I don't mean clean, I mean CLEAN!

Undo the engine shock if equipped. Remove the top bolt. Lift the engine slightly using a floor jack, engine cradle or hoist. If you use a floor jack be sure to use a block of wood between the pan and jack. Remove the heat shield (if it is still there), remove the two 6MM Allen bolts, curse a bit whilst finagling the old mount out.

You'll probably need to lift the engine a bit more when placing the new mount. Don't lift it any more than needed to slip the mount into place. Start the two Allen screws (I apply a bit of NeverSeize compound for future replacement ease), finger tight them. Replace the heat shield and start the large bolt. Tighten the 6MM Allen screws. You might need to remove the heat shield to get to the small Allen bolts. If you do then don't forget to start the large bolt before tightening the small bolts . Lower the engine. Do the other mount before you tighten the large bolts. Plan on doing some cursing and prying when aligning the large bolts.

Don't go crazy lifting the engine or you will tweak the throttle linkage. You could undo the linkage leading through the firewall just to be safe.
 

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'72 250C, '74 280C, '85 500SEL, '81 300CD.
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1,006 Posts
Might be a good time to replace the transmission mount AFTER you do the engine mounts.
 
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