The Engine mount, commonly referred to as the motor mount, is the most important stabilization device for the engine in the Boxster. With a deteriorating mount, there will be jerky shifts, rumbling noises while turning, and excessive idle vibration. You can see a video of a broken motor mount here:
You'll have to excuse me as I'm fairly new to making videos.
And the comparison of a new mount here:
I found the guides posted on Pelican and Pedro's guide to be good, but leaving out some useful parts and tips. I wrote these short pointers and tips to aid and help fellow forum members save some time and make the job easier. As with any jobs with working under the car, I recommend wearing some gloves to avoid the scraped knuckles you will get underneath out confined cars.
Guides referenced:
Install Front Engine Mount
Pelican Technical Article: Replacing Boxster Motor Mounts - 986 / 987
First off, jack up the car on all four jacking points. Both guides say you can back the car up on ramps but, as Mark Twain puts it, "There are Lies, damned lies, and statistics". Do not even try to do this job just using ramps, it will save you a lot of pain and anguish.
The rear underside is held in place with 10mm plastic nuts.
Here's a better picture of the motor mount location.
Here's what I found: The only time you can feasibly use a socket wrench is when undoing the engine case from the underside chassis of the car. The engine mount, affixed to the engine, can be removed with combination wrenches, mostly with the box side. Note that all measurements for the nuts and bolts used are 15mm.
The engine casing bolts removed. (They are 7mm bolt the nuts are 15mm)
I found the easiest way to get out the mount as seen in this picture. I found if you rotate it upside down, it's a lot easier to maneuver out.
Keep in mind to label the bolts and make sure you don't get them mixed up. In the event you do: There are 3 long bolts and 1 short bolt. The short bolt goes in the upper right hole, the three go in the bottom right, bottom left, and upper left hole.
Remember to document and label points well; it's even a good idea to take pictures. Yes, it's quite possible to install the the numerous components backwards!!!
Removing the engine mount from the engine casing:
Old vs. New
*Use loctite blue thread-locker on the threads when reinstalling the mount, these mounts go through a lot of vibration, so you don't want these things coming loose!*
When you're putting in the bolts back into the mount, it can be a bit tricky. You'll have to lower the engine up and down to find the perfect fit. For instance, the lower left bolt is impossible to place unless you lower the engine a few inches.
For the upper bolts, I could squeeze my hand in the cavity behind the engine casing and turn the bolts by hand until they had to be tightened by box end wrench.
I then reinstalled everything in reverse order, and enjoyed my new mount! The difference is indeed night and day.
Trivia:
*For those of you curious, my Porsche dealership quoted me $600+ tax for the job.
*Technically the Boxster uses an engine mount. Engines use internal combustion, while motors use alternative propulsion e.g. electricity. The usage of motor/engine mount depends on geography, but the later use of motor mount is more favorable as it rolls off the tongue easier.