Engine mount, replace one or both?
 

I was inspecting my motor mounts today. The driver side looks very good and looks almost new. The passenger side looks poor.

1.) Is it okay to just change the bad one or is it best to replace them in pairs?

2.) I've read the the DIYs and service manual and it seems like a fairly simple job. One thing I'm not clear on is do you unfasten both mounts and engine shocks before lifting the engine or is this done one side at a time.

3.) Should I go ahead and buy a new engine shock too. I have no idea how to determine if engine shocks need replacing. Engine just has a slight shake at idle. Smooth as butter on acceleration and cruising speed.

IMO, unless you have evidence that the driver's side was recently replaced, I'd do both. You are going to get greasy whether you do one or both and the mounts really aren't THAT expensive. Get good ones (Lemfoerder comes to mind).

I've read of folks doing one at a time, but I'm not sure why that is an advantage. The higher you can lift the engine, the better, and I would be worried about the stresses on the still-attached mount. Loosen the bottom mount of the passenger side shock but completely remove the shock with bracket on the driver's side. This will give you a little more wiggle room when removing the 8mm hex bolts there.

Some argue how effective the shocks are. Seems to me that they are most effective on shutdown, rather than smoothing out rocking at idle. I found that mine were still real stiff so figured they were OK. If they compress easily, they are probably toast. They are relatively expensive, IIRC, so I opted to reuse them.

Don't forget to check the trans mount.

I've replaced the engine and tranny mounts, checked the shocks, installed an offset key to the camshaft to correct chain timing, fiddled with the rack dampner, and I still have rocking (worse at hot idle). Next step is to rebuild/balance the injectors and time the injection pump. I know my injectors are original at 270k.

In my opinion, worn/unbalanced injectors are a major contributor to shaking, based on what I've read on the forums over the years.

You can change only 1 mount.

No need to buy a new Engine Shock; test it ounce you have it off. If it turns out you need one you can get one and install it later.

I cannot remember what the Engine Shock Mountings look like but the are Expensive. So I would take a goood look at them when you get the Car Jacked up and see which end of the Engine Shock Mount needs to come off so that when you Jack up the Engine you will not stress it.

I would also loosen the main single Motor Mount Bolt that goes into the upper Arm from the bottom on the side you are not changing the mout on before lifiting the Engine so that you do not stress the good Mount.

The main single motor mount bolt you refer to is the one from underneath the engine correct? So remove both underneath bolts on both sides I presume?

I recommend replacing both while you have the engine high enough to do the job right. the long through bolt will come out easy enough. before you get started I recommend looking at what condition is the engine bay specially around the two bolts that holds the mount on the support. If there's anykind of dirt in the bolt head it will be hard to get the allen wrench on to have a good grip.

Take your air blower and shoot the bolt head clean and try the allen wrench from the top to see if they go on easy. As mentioned you might not need the shocks unless your engine just shoot off violently, the new mounts should prevent that, at least it did mind. But if you like to have the extra shock absorber I am designing a cheaper method to replace the shocks and mount, parts are 20.00.

I post when the prototypes are done.

Answer
 

OM617 lower engine shock "Bushing"
http://www.peachparts.com/shopforum/mercedes-parts-reference-library/212385-om617-lower-engine-shock-bushing.html#post1749095

Engine mount
MB# 123 241 30 13

Fastlane: Engine mount
http://catalog.peachparts.com/item.wws?sku=W0133-1629653

I replaced my engine mounts last month. You have to disconnect both engine shocks and both engine mount bolts from the bottom going up into the feet on the engine, so you might as well replace both mounts. I think I paid about $32.00 for the pair.

I left the existing engine shocks in but I wish I had replaced them because it was such a pain getting the bolts to align through the new mounts into the feet that I'm not looking forward to taking them out to replace the engine shocks. It's easier to just do it at the same time.

Good Luck!!

Thanks for the input everyone. I think replacing is the best course of action since both will be unbolted for underneath anyway. It's my understanding the driver side can be a pain.

The drivers side is harder, but a combination of a allen socket and a regular allen wrench will get it done. I think you can do all four from above. As was mentioned, clean-out the heads of those bolts very well. The one closest to the engine on the driver's side is the worst 'cause you can't see it. A tip is to dip the end of your socket/wrench in Ajax to get the surest grip. It would be a good idea to use some never-seize on the bolts on reassembly in case you have to do it again.

In case you live long enough.:rolleyes:

As said, make sure the head of the 8mm long bolt from underneith is good and clean so the bit is all the way in. I use a hammer to make sure it well seated.
Using some valve lapping compound on the bit will make it bite into the head to prevent slippage, sometimes they are in there pretty tight. just give it a quick pull to break it loose. I use an 18 inch breaker bar.

The engine shocks have a little flat space on the lower end of the shaft for a wrench to keep the shaft from turning when removing the lower 10mm nut. I think it is a 7mm for the flats.

If you don`t remove the shocks, make sure the shafts are lined up with the mount holes when lowering the engine. I had one shock not line up and shoved the shock up through the upper shock mount :(.

Charlie

I generally just replace the one that is bad. They seem to deteriorate from contact with oil or fuel and my theory is one side goes bad before the other.

But you still unbolt both underneath bolts?

I had to change mine very frequently until I discovered what was causing the quick deterioration.
The reason was the fuel spilled on the mounts when changing the in line fuel filters, I now stack up towels and newspaper directly under the filter to soak up all the spill, that keeps the mounts nice and dry.

Vahe

I would recommend doing so. Last week I lifted my engine out and left one bolt in (it was stuck). It easily ripped the motor mount in half, freeing the engine...I imagine you probably don't want that to happen.

FYI
 

Heat shield OM617 engine mount
http://www.peachparts.com/shopforum/diesel-discussion/121452-heat-shield-om617-engine-mount-post873875.html

OM617 Motor Mount DIY
http://www.peachparts.com/shopforum/diesel-discussion/152804-om617-motor-mount-diy.html

Bad engine mounts
http://www.peachparts.com/shopforum/diesel-discussion/121286-bad-engine-mounts-post868339.html

Engine / motor mount DIY
http://www.peachparts.com/shopforum/diesel-discussion/146482-engine-motor-mount-diy.html#post1104023

300D engine mount blues
http://www.peachparts.com/shopforum/diesel-discussion/109264-300d-engine-mount-blues.html#post758340

One of the better reasons to change your motor mounts (pics)
http://www.peachparts.com/shopforum/diesel-discussion/102640-one-better-reasons-change-your-motor-mounts-pics.html