Date registered: Feb 2008
Location: Dallas, TX
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S430 S500 Engine Mount Replacement DIY
I had the very common "shaking at idle" issue so decided to replace the engine mounts. It totally solved the problem! The car is smooth once again. Anyway, it went pretty smoothly and took about 3 hours total time. Here is a write-up in case anyone finds it useful. Please let me know if I need to address any of the content!
• Open hood and remove the air intake ducts to allow room to work
• Disconnect the battery due to shock hazard working near the hot starter terminal.
• Jack up / lift vehicle to a moderate height that can allow access to the engine from the top as well as bottom. I set mine using a 2 post frame lift to about 30 inches from the ground.
• Remove the lower engine cover panel under the vehicle.
• Using a 13mm socket, remove both lower engine mount bolts and set aside
• Using a floor jack or suitable lifting device, raise the engine via a piece of wood under the oil pan. The engine can be lifted about 3 inches before the AC hoses begin to show signs of stress. I don’t recommend going much further than this!
• Lower the steering rack about 2 inches. Using a deep well 18mm socket , retain the nut inside the subframe channel on the two rear bolts. Using another 18mm impact socket or wrench loosen the two rear bolts. Do not fully remove the rear two bolts but make them as loose as possible while still keeping the nut on the bolt. Completely remove the two front steering rack bolts using an 18mm open end wrench and impact socket. This will allow the rack to hang down but still allow easy reinstallation.
• At this point it is necessary to remove the upper engine mount bolts. On the V8, there is little room for a socket due to the exhaust manifold. With the engine raised it’s much easier to do this step though. From the top use a 16mm ( or 5/8”) ratcheting box end wrench and loosen the bolts. They will not come out due to their length, but the engine mounts will drop off the bolts when they are loosened enough.
• From the bottom of the car, fish the right side engine mount rearward and pull out between the cat , bellhousing, and subframe. You may need to raise the engine a tad if it won’t come out. It may take a little finessing and tugging to remove. The left side mount will come out towards the front between the steering rack and subframe.
• Press the new mounts into the same areas the old ones came from. Get into a position under the car where you are supported and can hold the engine mount against the upper bracket with one hand and still reach the upper bolt with a couple fingers of the other hand. As you press the mount against the upper bracket, screw the bolt into the mount. Just a couple threads is all you need. Now spin the mount clockwise to tighten while keeping a finger on the bolt. After several spins, you will feel there is a place where the mount locating pin will pop into the recess on the upper mount bracket. At this point the mount will no longer spin. You can now go to the top of the engine and fully tighten the bolt to ~55NM. Tightening the upper bolt is much easier while the engine is lifted so I recommend doing now.
• Reinstall the two front steering rack bolts / nuts and tighen all four bolts to spec.
• Lower the engine slowly watching for the engine mount threaded holes to stay in alignment with the subframe holes. Mine required no side to side adjustment but could be necessary with a crow bar.
• Reinstall lower mount bolts using Locktite and torque to ~35NM.
• Reinstall air ducts, lower engine cover, connect battery and your done!