These motor mounts are rough! - PeachParts Mercedes-Benz Forum

Brewer · #1 01-27-2012, 07:30 PM

Need inspiration to finish replacing these motor mounts (85 300SD).

As soon as I started I realized all the hex bolts were stripped. Bought new sharp edged hex sockets for the job, but they just spin. I had even cleaned out the inside of the hex bolt really good before starting.

The google is no help because most of the common solutions involve being able to get at the bolt head. What do you do when you can barely reach the stupid things?

I realize I could take the arm of the engine block, but that doesn't seem any easier, and I still don't think I'd have a clear shot at these things.

I've resorted to aimlessly jabbing the rubber part, chipping away at it with a screwdriver...

uuuurrgg!

JamesDean · #2 01-27-2012, 09:22 PM

You could try chemically dissolving the rubber and then gain access to the bolts.

My 300SD mount was pretty bad, not AS bad as your but not too far. My bolts were 6mm alan bolts, are yours the same or are they standard hex? I dont think theres enough clearance to get a standard hex + socket in there...

A quick google search says Naphta, petroleoum, turpentine, or ether will do the trick, but all of those will dissolve paint as well!

You can keep chipping away at the rubber then get a long 6mm alan socket and have at it. This was not a fun task on my SD even less on the 560SEL

Diesel911 · #3 01-27-2012, 10:25 PM

This might not help you now but some Allen type sockets are not flat at the end making for a reduced gripping area; hope you can see in the pics.

I ground down the one so it was flat.

You may be at the point where you need to do what will most likely work instead of what is might be the easiest. This means you would have a better chance of success removing the whole Arm one at time.

Ther might be something below as others have had the same problem.

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Some have had luck dipping the end of the Allen in a gritty compound.

Beating a tight fittingv Torx bit into the Allen Head.

On a smaller Allen Head Bolt I actually epoxied the Allen Wrench in to the head of the Blot and used one of those Manual Impact Wreches that you hit with a Hammer. (Because you hit it with a Hammer and it rotates at the same time the force of the Hammer helps hold the bit in place pushed against the Bolt.)
In the end it depands on how buggered the hole that the Allen Head goes into is.

79Mercy · #4 01-27-2012, 10:35 PM

i had to deal with this on my W115, i was able to hammer a 12point 12MM socket over the head of the stripped 6mm allen bolt, works like a charm.

Now it was hard getting the bolt out of my good socket but i finally got it out.

Biodiesel300TD · #5 01-28-2012, 12:27 AM

Quote:

Originally Posted by 79Mercy

i had to deal with this on my W115, i was able to hammer a 12point 12MM socket over the head of the stripped 6mm allen bolt, works like a charm.

Now it was hard getting the bolt out of my good socket but i finally got it out.

I've done this as well. Works every time, but you have to make sure you get the 12point hammered in all the way.

Brewer · #6 02-02-2012, 08:20 PM

thanks people. the 12 point 12mm socket trick worked great.

now for the other side... the bottom 8mm bolt is stuck, too. I'm trying to google what 12 point socket to go over that one? a 14mm?

Brewer · #7 02-24-2012, 07:36 PM

For completeness sakes...

for the bottom bolt, you can't hammer a 12-point socket onto it, because it's up in a recessed area. However, drilling it out is very easy and works great.

Also, I had trouble getting the inner 6MM bolts on each side. But I found after getting the outer bolts off, and pushing the mount back and forth... it breaks the inner bolts loose and they can be removed easier.

Finally for the passenger side, I definitely had to remove the air filter and the air filter mounting arm...

Clemson88 · #8 02-24-2012, 11:55 PM

I decided to replace my mounts when the PS pump pulley bit into the hose that goes from the oil filter housing to the oil cooler. The entire job cost about 300 buck. Yes, the mount failed and lowered the left side of the engine two or three inches. Ignorance is not bliss.

I had to remove the arm on the right side of the car and use a grinder to get the mount off the arm. The bolt was $1. I still haven't gotten the oil off the white paint on the engine compartment but I swear as soon as spring arrives...

Desert Panther · #9 02-27-2012, 02:42 PM

I'm curious how many hours this job takes? I have a 123 coupe that needs mounts replaced badly. Is it pretty much the same job, since it IS the same OM617 engine?

Orv · #10 02-27-2012, 02:48 PM

Quote:

Originally Posted by Desert Panther

I'm curious how many hours this job takes? I have a 123 coupe that needs mounts replaced badly. Is it pretty much the same job, since it IS the same OM617 engine?

Seems to depend pretty much entirely on how mangled the old ones are. A lot of the grief comes from having to deal with hardware that's been damaged or misaligned by the engine thrashing around on bad mounts.

daw_two · #11 02-27-2012, 02:54 PM

This reminds me to grab the extra 603 engine arms off the 350SD in the junkyard.

Desert Panther · #12 02-27-2012, 03:41 PM

Quote:

Originally Posted by Orv

Seems to depend pretty much entirely on how mangled the old ones are. A lot of the grief comes from having to deal with hardware that's been damaged or misaligned by the engine thrashing around on bad mounts.

Thrashing around, LOL! You are describing my car to a "T"

So, any idea on the hours?

Biodiesel300TD · #13 02-27-2012, 03:48 PM

Quote:

Originally Posted by Desert Panther

Thrashing around, LOL! You are describing my car to a "T"

So, any idea on the hours?

When I did mine the first time it only took a 3 or 4 hours. The second and third time I did it, it only took me about half that. If all goes well it's goes pretty quick. Make sure to clean all the allen bolt heads out really well. And make sure they are threaded in properly when you install them. It's really easy to bugger up the threads in the aluminum mounting arm, asking me how it know

Also if your motor mounts are toast you'll probably want to replace the trans mount as well.

Desert Panther · #14 02-27-2012, 04:22 PM

Quote:

Originally Posted by Biodiesel300TD

Also if your motor mounts are toast you'll probably want to replace the trans mount as well.

Now that you mention it, I should've thought of this ahead of time! Mine is probably shot as well. Can the trans mount be replaced at a later date, or is it an enormous amount of work once the new motor mounts are already in?

54dan · #15 02-27-2012, 04:34 PM

The trans mount is comparatively a piece of cake and can (and should) be done independently of the engine mounts. It's basically the third leg of a 3-legged mounting system (L and R engine mounts, trans mount on the tail of the tranny).

To replace it, you simply support the tranny (jack it up a little), remove the trans-mount nut at the top of the mount, remove the four crossmember-chassis bolts, remove crossmember, take out two bolts that attach the mount to the crossmember, remove old mount.

"Installation is reverse of disassembly," to quote Mr. Haynes.

I leave the mount loose until everything is in place, then tighten it all down.

Hope this helps.

-Dan