000lynx

Hi Guys,

I just wanted to post this write up because I just finished doing the Engine Mounts + Transmission Mounts on my 2014 GL 500 X166 V8 M278 Engine. I didnt find a write up online for this model and wanted to help out others doing this job.

Why do this job? You will want to replace your Engine Mounts and Transmission Mounts if when you launch your car you feel a jerk or a clunk. The V8 in this car is big and obviously with time the rubber wears out and needs replacing. After you replace it, it will be smooth as hell.

Genuine Mercedes Part Numbers:
1. Driver Side Engine Mount: 1662406117 ($139 USD
2. Passenger Side Engine Mount: 1662406017 ($139 USD)
3. Transmission Mount: 1662401118 ($65 USD)
(I purchased from Model Automotive in the UAE)

Tools Required

1. Trolley Jack preferably one that can lift beyond 450mm but otherwise any Trolley Jack capable of 1500kg+ and some wood to add on top.
2. A pair of Axel Stands
3. E-Torx Set that has numbers 10 through 18. (I think you need 10, 11, 14, 16 and 18)
4. A Socket Set including angled-adaptors to get that nice angle.
5. A Breaker Bar
6. A set of Ratchet Spanners / Ratchet Wrenches (i think you need size 8mm and 10mm)
7. A number of 1/2" Extensions. I needed around 750mm of extension which was around 6 extensions pieces of varying lengths. (This is to get to the E18 Torx Bit holding Engine Mounts)
8. A Magnetic Light to stick to the side of the chassis so you can work and see underneath the car.
9. A magnetic bowl and pickup tool to grab any bolts that drop in funky places and to hold bolts (this isnt required but helpful)
10. You do NOT NEED the 16mm Mercedes Offset Wrench some people talk about for Engine Mounts for this job on this car. So dont buy it. (I did, never used it) The mounts are smarter on this car.

Important Video: This guys youtube video is a nice shot of the Engine Mount removals. Take a look once you have read this guide.
Engine Mount Procedure
1. Jack the car from the centre of the Jack Point and insert two Axel Stands in the points as marked below. Caution when buying a cheap trolley Jack, they dont usually jack very high. The height of my Stanley one was 385mm but even still I had to use two pieces of wood and I could only get to the first rung on my Axel stand. Jacking higher now and using a higher rung on the Axel Stand will give you more clearance underneath and make the job a little easier. Chock the rear wheels once its lifted using a brick or some proper chocks


Jack and Stand Positions

2. Remove the 2 x Plastic Chassis Protector Trim pieces.

• These are the plastics underneath Mercedes Cars protecting all the bits like the bottom of engine and transmission from crap and gunk
• remove the smaller one first closest to Transmission then remove the larger one. They use 8mm Screws with large washers on them.
• Put the plastics pieces aside (Tip: to place all the screws back into their holes so you dont lose them!)

Driver Sound Engine Mounts -
Removing the Exhaust Pipe
3. Great, so you've safely jacked the car, inserted Axel Stands and you've used your scissor jack from the boot to be positioned under the control arm or some other safe, strong metal point
The next step, you'll need to remove the Exhaust from the Drivers or Passengers Side. It doesn't matter which, I started on Drivers side. Just a tip, X166 can be tight in some places, and all the E-torx I had for this job were either 3/4 or 1/2" so sometimes converting down to a 1/4" is a good idea to manage the space you've got.

• Remove the two E-Torx Bolts connecting the Exhaust pipe to the Exhaust Manifold.
• Loosen the Clip on the Rear of the Exhaust pipe that joins the Front section of the Pipe to the Resonator. The exhaust will now just drop out.
• Reach your hand up and unplug the 2 x O2 Sensors attached to exhaust. Dont unbolt them, but unplug the plugs. The plugs are easy to unplug and this way you wont damage the sensors. The plugs are positioned in a metal bracket so they dont flap around while driving, so I believe you push one UP toward the roof and the other comes out sideways I think but just take your time and figure it out and then unplug them.
• Remove the cross member brace that is sitting underneath the exhaust and stopping it drop (I actually removed the driver side bolt and just swung it out of the way).
• Place the exhaust on some cardboard or mat to protect it from scratches and keep it on the drivers side of the car so you can keep track of the LH and RH parts on this job.

4. Remove the Heatshields (DHS)

1. There are two Heatshields. One protecting the Chassis Area, its the larger one marked Heatshield 1 in Red in the below image. The second one is protecting the engine mount, its smaller and made of a smooth aluminium not a dimpled one.
2. Heatshield 1 has 2 bolts
3. Heatshield 2 has 3 bolts but 2 come completely out, the other just needs to be loosened and stays there, the way it works is Heatshield 2 has a grove that goes around the bolt like a clip and tightens by the bolt so there no need to compactly remove it. Its actually connected to another heatshield further up the engine and which we dont need to remove for this job.

Honestly, this took me like 1 hour for the first time. Its a real pain in the *** the bolts are annoying and I didnt bring the right tools. Ratchet Wrenches are very handy here!


5. Unbolt the Driver Side Engine Mount

1. Unbolt the bottom two bolts which hold it in place, they are easy to unbolt and are size E14 I believe - E-Torx.
2. Use a breaker Bar, an angle socket and around 750mm of extension and try your best to break the Top bolt which is an E-18.

This is extremely difficult. Its hard to explain but - You need to get the breaker bar extended out far enough so that you can position the HEAD of the breaker bar against the chassis (so the whole setup doesnt slip off the bolt) and then PULL as hard as you can and BREAK the bolts tightness. If you try and hold the breaker bar with your hand and use your other hand to pull you wont have the strength its too strong (or mine was anyway). Make sure you dont strip it

Once its broken move onto the next step which is unbolting the OTHER side engine mount (and then jacking the engine to pull them out and replace them).




Good job so far! This took me about 5 hours to this point because I just did everything slowly. Took me ages to jack the car because I was being cautious! haha, I imagine it takes the Pro's less than 45mins to get to this point! Now, do the other side.

6. Remove the Passenger Side Exhaust

• The passenger side is more tight because the drive train is in the way. Thats okay though, youll be able to do it.
• Repeat the same process as for the Drivers Side - Unbolt the exhaust, Unplug the O2 Sensors and remove the Cross Memmber Brace (Although the brace looks different on this side.)
• The Cross Member Brace has 4 x 16mm bolts and 2 of the bolts are greased. Dont wipe off the grease, if you do, put it back. Dont know why its there, but its there for a reason. Use a 16mm Deep Socket for this one.
• Unbolt the Engine and put it on the Drivers side. Dont scratch it.

7. Unbolt the Passenger Side Engine Mount

• Well, now you're an expert because you just killed yourself unbolting the Drivers side. So this is easy! But seriously jokes aside, I found this whole side muuch faster
• The only difference was, for some odd Reason, I COULD NOT remove the Engine Mount Heatshield (which if you remember is Heatshield 2 in blue above). So I just unbolted what I could (2 bolts ) and kind of pushed it out of the way when I was pulling the mount out. It was very annoying though.
• Unbolt the two smaller bolts for the Passenger Side Engine Mount
• Use the breaker bar setup and Unbolt the Top Bolt

8. Jack the Engine, Remove the Mounts

• Ok now we are at the business end.
• FIRST, Jack the Drivers Side of the Engine more, I did this by place a long piece of wood under the ENGINE OIL PAN (note there are two oil pan looking things. One is for the Engine one is for the Transmission. The engine is the smaller one up the front (Duh!)
• Place the piece of wood more onto the drivers side of the engine and stick it out a bit past the oil pan (rather than in the centre) This will jack up the drivers side a bit more giving you more clearance to remove. Do the opposite when raising the Passenger side to give more clearance there. The reason is if you jack the whole thing up from the centre, I couldn't jack it enough to get the clearance. ALSO be really careful not to raise the engine too much - I did and it split my air intake hose ($60 replacement) So just do it bit by bit, get under and check if you have enough clearance, if not, jack up a bit more. Dont just jack the hell out of it then get under and yank it out - thats careless!
• NOTE: This is seriously dangerous if you screw this up. You could split your oil pan. You need to be REALLY careful here. See the below picture to explain how to jack.
• 
  
• So Jack the engine up the drivers side, then pull the mount out. It takes a while to wiggle it free but be patient. Put the new mount in
• Jack the engine up on the passenger side and then pull the mount out there too. Put the new one in.
• When you put the new mount in, Bolt the TOP BOLT in (dont tighten the hell out of it) but do it up tight so you can lower it in the next step

9. Align the Bottom Holes, Lower the Engine and seat the mounts into place

• This part is tricky. I just thew my mounts in and dropped the engine. It wasnt good. They did not line up.
• What worked for me was bolting the top bolt and carefully lowering it a few mm at a time AND MOVING THE ENGINE MOUNT INTO POSITION AS I LOWERED IT. Do this with an extender Bar from the socket set. NOT YOUR HANDS LOL!
• I did this for Driver side first, then totally bolted it up and then did the Passenger side.
• The mounts must be aligned correctly. There is a groove on top. Ensure it aligns with the groove on that side, use your phones camera to take a photo of the inside of the housing on the engine then align the mount the correct way so when its lowered onto the mount it'll be in the right spot. See photo below:
• Another thing is on the PASSENGER SIDE I used a long flat head screwdriver with the engine raised to angle it correctly and had a 2nd person lower the engine slowly. You need to understand that you must align these mounts back into place whichever way works for you. You cant just drop the engine they wont align which is very annoying. You will know when its aligned because the two bottom holes will match up perfectly and youll be able to bolt them in!

Here is a photo of a nice brand new engine mount.


Ok so now we have the two NEW mounts in, the Tops are bolted and you've likely bolted the bottoms on one side, just do the same on the other side and lower the engine completly. Move onto the next step, which is to now do the transmission mount! Well done for getting this far.


TRANSMISSION MOUNT REPLACEMENT
(Much easier than engine mounts - takes 15mins)

1. With the exhaust and everything off from the engine mount job, jack the transmission using wood. You need to jack it say half an inch, not much at all basically supporting the weight and then a tad more.
2. Use the scissor jack to hold the transmission oil pan up (dont raise it per se, but apply slight pressure so if the transmission jack with wood setup fails, its still supported. Safety first.
3. Unbolt the two bolts on the transmission mount
4. Remove the main cross member. This is 3 x 16mm Bolts on one side and 3 x 16mm bolts on the other. Its heavy too.
5. now you can see the Transmission Mount which has 4 x E-Torx bolts. Take them off.
6. Replace the Engine mount with a new one. I dont believe there is any orientation here that matters.
7. Tighten the 4 x bolts
8. Replace the Main Cross Memmbers 6 bolts
9. Replace the two bolts on the Transmission threads
10. Lower the transmission
11. Tighten the two Transmission bolts again from Step 9 because you have lower the transmission which gives you more slack to tighten up
12. You're done!!

Congratulations, you did it! I hoped this helped those V8 X166 owners out there!

texas008

Thanks for the write up. it also helped X164 owners

chassis

Thanks.

Torque specs?

Did you consider lifting the engine from above rather than jacking from the oil pan?

freddieZ

I did some research on replacing the engine mounts for our W166. If you want to lift it from the top, you will need 240589006100 - Engine Lifting Fixture, which costs more than $4,000. I would rather lift it from the bottom.
When you do your work on W166 instead of X166, I think you should take out the air filter and the air intake hose first. The torque specs are all 53 Nm for the bolts on the mount.
Thank you for your ownership report btw! I did many work based on your threads.