Urethane filling N55 mounts


Jan 23, 2018
I had this mount sitting out of the car while I work on a custom turbo setup and couldn't help but dissect and "upgrade" it.

Here you can see where I've removed the rubber and plastic top caps that insert into those four holes. I then drilled through the partially obstructing edges of the black mount through the same four holes, to allow better application and flow of the urethane. Shake out the rubber debris and blow it out with compressed air when your done. I hit it with a little brake cleaner and then blew it out again to clean and dry things nicely.


After that, get to filling! Stuff the nozzle into one hole and fill it slowly. Eventually you'll see urethane oozing out of the adjacent hole. Switch to filling that hole around then and continue filling for a while, allowing some excess to ooze out of the hole next to it. After that, smooth it down and move to the two holes on the other side and do the same thing.


Fill in the voids around the upper, exposed portion of the mount and you're done. Let it cure for as long as you can. A day at the very least, closer to a week if you can. Urethane cures with humidity, so the encapsulated portion inside of the mount will take a LONG time to fully cure.


Since I had some urethane left, I filled the xDrive transmission mount, too.


BTW, here's what the inside of the mount looks like. I don't advise going this far, since I think most of the benefit will come from filling through the top. I just wanted to see what was up inside of this thing and ended up going a step too far.

Plastic cap cuts off with a porta-band or hack saw.

First layer of black rubber diaphragm cut away exposes a type of hydraulic reed valve assembly for damping purposes. The aluminum mesh breaks apart easily with needle nose pliers.

Captured rubber reed valve between two "mesh" port layers.
IMG_20200912_093028 (1).jpg

Last layer of aluminum "mesh" out. One more black diaphragm to cut out. You can see the oil filling here. It oozed out from the moment I cut into the first diaphragm.

Pulling out that last diaphragm, you can see the white rubber layer that's bonded to the internal circumference of the mount shell.

The black area at the center is where the upper black EPDM rubber is bonded to the internal natural rubber colored piece.

You can section and remove the damper valve assembly. From there, I cleaned and trimmed away any remnant of black diaphragm.

Then I went too far and thought this was another fluid diaphragm. It's not. Don't cut it out! The "natural" rubber IS the mount. Leave it be.

Here's mine "reassembled". I drilled 4 holes, not shown here, through the natural colored rubber to allow urethane flow and filling from the back side.

All "fixed"!!!


Jan 23, 2018
Looks like an aftermarket N54 mount with exposed bushings. N54 is way hotter than N55 through the downpipe space, I'm sure.

With the stock mount filled like mine, there's really no urethane exposed to direct heat. The engine bracket shields most of what little is exposed. I doubt heat will be its demise. Whatever does come of it, I'll post up.
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