How to change engine mounts

[Parrot of Doom]

At 176,000 miles the engine mounts could do with changing. The car shakes slightly when the engine is killed, and the steering wheel vibrates gently when idling. Not things a Merc should do. Job should take about 2 hours, no more.

The car is an E300TD, OM606 engine.

Tools required:

Ramps
Scissor jack (or trolley jack but scissor is easier)
Big blocks of wood, railway sleeper thickness
Sockets, ratchets, extensions including a flexible extension


1) Put the car on the ramps, parking brake on, gearbox in P. Chock the rear wheels.

2) Remove the 2 plastic trays protecting the engine, and the transmission. 8mm bolts.

3) The mounts are easily spotted. They're also quite accessible.

4) Each mount is held to the chassis by two bolts. One on top, one below. The bolts below are a doddle to reach, holes have been cut in the chassis to allow a socket through. Its the bolts on the topside that are a bit tricky, however they're not too difficult.

These images show the location of the mounts, from underneath the car, and the location of the bolt on the nearside mount. Top bolts are 16mm.

You can see how easily accessible it is. Unfortunately, the top bolt isn't quite so obvious. You have to reach around with a spanner and undo it blind - unless you remove the intake manifold, which is job for another day really. Fortunately, the offside mount top bolt was barely fingertight so not an issue.

Just like removing a wheel, its important to loosen both bolts before you jack the engine up - this makes removing the bolts much easier before you place massive strain on the engine by jacking it.

5) Move your scissor jack into position underneath the oil pan, and carefully raise it up. If required, put a block of wood underneath the jack to get the necessary height.

You will need to put a block of wood between the oil pan and the jack, to spread the load over a wider area. You don't want the jack punching through the oil pan, or distorting it in any way. Wood is nice and soft, so is ideal for this.

MAKE ABSOLUTELY CERTAIN THAT EVERYTHING IS SECURE AND WON'T MOVE AROUND BEFORE YOU JACK THE ENGINE UP

6) Jack the engine up about 1/2 to 1 inch - no more should be necessary. Now, go to the nearside mount, unscrew the remainder of the bolts top and bottom, and it should come out straight away. They don't weigh much, but don't let it drop on your head!

If you look at the top rubber sections, you might be able to make out a large crack running around the circumference of the mount. You can also see the top locating pin.

Here are the old and new mounts together. Note the difference in height - I'm uncertain if this is wear/tear, or different design. Probably a combination of the two. Certainly the engine mount I bought (MB OEM) was different in several ways, most obviously the use of more rubber (not visible in the pic)

7) Pop the new mount in place. You may have to jack the engine up slightly, as the new mount will be slightly taller than the old one. Be careful not to push it up too far, keep an eye on the fanblades and exhaust. Ensure that the top locating pin fits correctly into the mounting area, and screw both bolts in place. Lower the jack slightly and let the mounts take the weight of the engine, and tighten both bolts up securely.

Let the jack down completely, and for good measure give the bolts another bit of a nip.

 

[Parrot of Doom]

8) The offside mount is a bit easier. The bottom bolt is just as simple to remove as the nearside mount. The top of the mount is different. A metal bracket holds the exhaust heatshield in place, and the bolt for the mount passes through this bracket. In this picture, you can see the bracket, the bolt that holds the bracket, and just underneath my mate's fingers is the top bolt for the mount. The tube running diagonally through the frame is the gearbox dipstick tube.

You don't need to remove the bracket to get the mount off, so leave that alone. You will need a flexible fitting for your ratchet, like this:

The cloth is optional!

Loosen both bolts, and jack the engine up again, remove the bolts, and pull the mount out.

Now I found something very curious here. Each mount has a different part number. The two new mounts that I bought, one had splines on the base, the other had a smooth base. Yet as you can see here, both old mounts had splines on the bases. The splines appear to do nothing, the locating elements of the base are the 4 dowel sized indentations on each mount.

Theres a bit of crud on one of them that looks like a pin, its not, its just crud.

I have no idea if theres any difference - I think 99% not. I think the part numbers are kept different for book-keeping purposes. Both mounts were absolutely identical in every respect. There were no issues whatsoever with the new mount with a smooth base. I think its just one of those things. If anybody knows otherwise, please let me know.



And there you have it. Pretty easy job. A couple of times while out driving I thought the engine had stalled. The steering wheel previously vibrated slightly, now its a barely noticeable murmour at idle.

Hopefully now I can get the belt tensioner problem sorted

 

[stats007]

Nice write-up. Are they oil filled? The splines I can only assume have a stiffening / directing effect ?

 

[television]

I do not want to side step your super thread, seing the engine mounts reminds me of the recent car show MechanicEX, we were shown a top suspension rubber that goes on top of the spring, "was it ok" we were asked and the answer was yes. We were then shown a new one that was 1" higher than the first one.The first one had collasped and would have got refitted.

So what I am trying to say is that though a visual inspection says a lot, in the case of engine mounts, replacement is the only way to go. Its always over looked and forgotten sitting under the engine, all of that weight sitting on those two little blocks. Once the mountings have dropped, the whole drive train is out of line, and working overtime, all the U/J's working more than they need to.

Thank you again Parrot for a super article, It makes goog reading and sense.

Malcolm

 

[Parrot of Doom]

Nice write-up. Are they oil filled? The splines I can only assume have a stiffening / directing effect ?

I think they're there just to strengthen the bottom of the mount, I can't see any other function. They don't even rest on anything.

I don't know if they're oil filled, they're certainly non-serviceable. You'd have to butcher them to pull them apart, and I couldn't be bothered, I binned them

 

[Parrot of Doom]

Malcolm what do you think of the differences between the two new mounts?

http://homepage.ntlworld.com/tom.jeffs4/car stuff/merc tech/engine mounts/nearside mount 4.jpg

In that pic, the new mount is on the right - ignore the one on the left. Now, the other new mount had more rubber around the bulge in the centre. It also had a flat base, whereas the one in the picture has splines on the base. The physical dimensions are identical though, all the holes are identical, everything else.

I'm flummoxed, I can't think why they'd be any different, other than one is near the exhaust manifold - but its shielded anyway.

Different manufacturer perhaps? I can't think of a valid reason why they'd be different. I'm presuming the internals are the same. I'm slightly worried that theres a 50/50 chance they're on the wrong sides.

 

[television]

Malcolm what do you think of the differences between the two new mounts?

http://homepage.ntlworld.com/tom.jeffs4/car stuff/merc tech/engine mounts/nearside mount 4.jpg

In that pic, the new mount is on the right - ignore the one on the left. Now, the other new mount had more rubber around the bulge in the centre. It also had a flat base, whereas the one in the picture has splines on the base. The physical dimensions are identical though, all the holes are identical, everything else.

I'm flummoxed, I can't think why they'd be any different, other than one is near the exhaust manifold - but its shielded anyway.

Different manufacturer perhaps? I can't think of a valid reason why they'd be different. I'm presuming the internals are the same. I'm slightly worried that theres a 50/50 chance they're on the wrong sides.

This is always the worst quandary to be in when starting a job and the replacements have different part numbers.

looking at the photo you can see that the one on the left is deformed on every other step on the rubber.
The one on the right was more than likely made by someone else as car manufactures normally have more than one supplier, the extra rubber around the center is only mould rubber and means nothing. the splines in the base are only there to give a better bonding for the rubber, it also gives it more than twice the strenth.
In my veiw it is correct.

Malcolm

 

[Parrot of Doom]

Thanks. I could only think of two reasons why they might be different - because of the position of the exhaust manifold, and because of the direction of rotation of the engine.

I think the worst that could happen is premature failure of one side, but I doubt that would happen for many years/1000's miles so I think I can rest easy



Oh I should also add that one of the mounts, when unboxed, was sat in a big bit of floppy rubber - like a swimming cap - to protect while shipping I presume. Must be different manufacturers then.

 

[television]

Thanks. I could only think of two reasons why they might be different - because of the position of the exhaust manifold, and because of the direction of rotation of the engine.

I think the worst that could happen is premature failure of one side, but I doubt that would happen for many years/1000's miles so I think I can rest easy



Oh I should also add that one of the mounts, when unboxed, was sat in a big bit of floppy rubber - like a swimming cap - to protect while shipping I presume. Must be different manufacturers then.

Rubber is a funny thing... when packed in an air tight bag/packing it will last forever, as soon as it is exposed to air,it start to de compose. I learnt this from a rubber drive belt manufacture some time back. I do not know how much natural rubber there is in these things, silicon rubber used around windows etc is something else, could be a mixture of both, as used in tyres, and far less pervious to oil and heat.

Malcolm

 

[Myros]

Parrot

that was one hell of a how-to. You can come around and do my propshaft doughnuts anytime you like.
BTW, I think they are oil-filled, that might be why they are so good at damping.

 

[television]

Some more info here

http://autorepair.about.com/cs/doityourself/a/aa010304a.htm


Malcolm

 

[stats007]

Some are definitely oil-filled - R129 ones are.

 

[big x]

A 202 240 28 17 ENGINE MOUNTING FRONT LEFT replaced by A 203 240 06 17
A 202 240 30 17 ENGINE MOUNTING FRONT RIGHT

I suspect that due to rotational forces the damping rates are different.The
right is stiffer.

BTW When the rubber splits the oil oozes out and they collapse slightly.

adam

 

[anyweb]

excellent howto from POD

I will bookmark this should the need arise on my car,

once again, EXCELLENTLY done, many many thanks

any chance you'd do one on the AIR-CON system ?

heh
cheers
anyweb

 

[Parrot of Doom]

Nowt wrong with my aircon I tend to do things that need doing. I still haven't gotten around to cleaning out and refilling the diff, its this ****** weather

I think I'll just have to wait for it to stop raining, and have a look under there.

I think 3017 (front right) is on the nearside, so I think I'm ok. I'm going off memory and the photographs, the shot I lined up of the old and new mounts shows the nearside mount and it's replacement, and the photo shows 3017 on the side.

Its a good job I posted this thread otherwise I might have been none the wiser - although I think the worst that could happen is...not a lot really. Premature failure after a few years perhaps, certainly nothing catastrophic.

 

[Parrot of Doom]

For future reference, I have found some stock images of the two shocks.

Left (offside) mount:

Right (nearside) mount:

 

[Parrot of Doom]

Crumbs. They're on the wrong side - 3017 should be under the exhaust manifold.

Oh well, back to the drawing board!

 

[brandwooddixon]

Later today I'll be attempting to change the engine and gearbox mounts on my 1998 E430, picked up the mounts from the dealers yesterday (£179 in total - egnine mounts £75 each).

I'll post any significant diffulties that I note here later.

Points that I've noted so far:

1. For the V8, both mounts have the same part number, so no problem with handedness.

2. The gearbox mount is officially referred to as rear engine mount in the Benz workshop system, but they knew what I meant.

3. It looks as if I'll have to remove the fan shroud from the radiator.

4. Access from the top is going to be tight, I'm hoping that I can access everything from below.

 

[toby1]

8) I have no idea if theres any difference - I think 99% not. I think the part numbers are kept different for book-keeping purposes. Both mounts were absolutely identical in every respect. There were no issues whatsoever with the new mount with a smooth base. I think its just one of those things. If anybody knows otherwise, please let me know.

One possible reason is the supersession of the part number over time. I have access to supersession histories for MB parts. If you want, you could give me the part number you fitted and I'd be happy to check for you.

It could just genuinely be the improvement of a part over time, or perhaps a different manufacturer.

(I've just noticed Big X's reply! Doh!)

 

[Parrot of Doom]

3. It looks as if I'll have to remove the fan shroud from the radiator.

Very easy to do on mine, it just unclips - however I found that the blades of the fan could quite easily get past the shroud, as the engine swings up from the back rather than coming straight vertically up.