Motor Mount Bolt-HELP!
 

Hey all!

I'm about to change the motor mounts in my 1991 300E W124 and I've been reading in the various forums how much a PITA the driver's side bolt is-so I took a look.
How do you even get to it? I can barely SEE the mount much less get a wrench on it. Please, I need tips, suggestions, and insight in how the top bolt is supposed to be removed. Any special tools needed? Do I get to it from under the hood or under the car?
Any and all suggestions would be appreciated.

Nick

pick it up, use a short 17mm wrench, like 5-6'' long and then use a long, strong pry bay against the crossmember. a real 1, not harbor freight or other taiwan stuff. even then, it's no fun. good luck, chuck.

Chuck

Should I lift just the engine up about an inch or so (since the mounts have collapsed) with a hydrolic jack and a 2x4 under the oilpan or am I picking up the whole car to be able to get under there?

1991 300CE

Here is what I did:

1) Release shroud surrounding fan. When you raise the motor, the fan blades will go well above the shroud. On this car, just twist off the ring part of the shroud and rest on fan blades.

2) Put front wheels on ramps. Chock rear wheels.

3) Work on the left upper bolt first. If you can't get this one, no sense in doing anything else.

a) Do it like porkface mentioned.

b) I threaded a long 1/4" extension down in a gap in the intake manifold, just behind the EHA. It is pretty much a straight shot if you are in the right hole. Have someone hold the extension, while you are below attaching it to a 17mm flex socket. A universal and regular 17mm socket may work. Be careful here as there is a lot of delicate linkage around. Make sure you are on the bolt solid and break it loose.

c) I used this method on a Lexus LS400. Put stubby 17mm box end of wrench on the bolt.
Use the female end of a long 3/8" extension on one of the tines on the open end of the stubby and give it a good pop with a rubber mallet.

4) Remove 8mm allen bolt under each mount. Right upper bolt is easy.

5) Raise motor with piece of wood under oil pan. Watch the motor as you raise it. Initially the motor won't move as you take up the slack in the suspension. Raise, check to see if you can pull out the old mount, raise, check, etc. You'll need to raise it a bit more to get a new full sized mount in.

Nick, for adequate access to the engine mounts recommend raising the entire car off the ground 9" to 12" ... place a stack of pieces of 2" x 6" wood under the tires, or a short piece of 6" x 6" under each jacking pad.

As you have realized replacing the driver's side engine mount is far more difficult than the passenger's side. When I recently replaced the engine mounts in our 1995 E320 I removed each engine mounting bracket with the engine mount attached. Then attached the new engine mount to the engine mounting bracket and reinstalled the assembly. That approach was easier than attempting to remove the bolt attaching the engine mount to the engine mounting bracket with both in place.

I plan to do this on the weekend. Is it really that straightforward?

If you are not able to break the top mount bolt then this method will work too. The four bolts on each engine mount bracket are reasonably accessible. Flex sockets are helpful.

Flex sockets for the 13mm bolts? My 17mm top bolts are clean, dry, and gray -- no trace of rust -- but I will at least try to loosen them while still on the car since, if they are seized, it will be harder for me to remove them when off the car.

After reading some more threads, and also seeing the below recommendations, I will definitely remove the brackets entirely:

Eric, be sure to remove the fan shroud before jacking up the engine. After the new engine mounts are installed reinstall the fan shroud so the fan is centered in the fan shroud.

Yes, flex sockets for the 13mm bracket bolts should make them easier.

Big time saver to break the top bolt loose, worth investing some time in a lever system. Without air tools the four bottom bolts are a bit time consuming and then off the car you have to somehow secure the bracket to break the top bolt loose, and then do the whole thing in reverse. Either way works.

The bolts to the engine block were a big concern; I know they will not come out easily.

Looking down into the engine bay I have a clear view of both mounts. The passenger side top bolt has limited overhead clearance because of the exhaust manifold, but a stubby wrench should break it free. (I have a 24'' pipe I slip over the handles of my wrenches/ratchets when I need added leverage.)

If I loosen/remove the top and bottom 17mm bolts and jack up the engine, I am assuming the mount bracket will simply separate like a clam shell, and then I can swap out the mounts?

Hey everyone!

I see my post was revived, so as a follow up...

I soaked both upper motor mount bolts with a corrosion spray (forget the name) for about 3-4 days before the job.
I jacked the car up and was able to get a 17mm socket on the bolt using a stubby ratchet from under the car. Now I don't know if the corrosion liquid did it's job or the bolt had loostened up from all the shaking the car was doing but it came off almost too easily. Once that was off, the rest of the job was a piece of cake.

Nick

Giving the bolts a spritz of penetrant ahead of time is a good idea. I always forget this.

I am just a DIYer and not being a working mechanic I never understood the idea of prying on a wrench. I recently did the engine mounts on my W202 and used this prying technique. You get a stubby wrench on the top bolt, put your pry bar perpendicular to the stubby and against something solid and pry. All you need is one good pry to break the bolt loose.

All looks good. And for clarity, if I leave the bracket attached to the engine block, I need only loosen the top bolts on each mount, and not the bottoms, correct?