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DIY Urethane Motor Mounts

This DIY describes the process of filling the XD's motor mounts with urethane. The XD has a lot of “wiggle room” in the stock motor mounts. This causes serious wheel hop issues on “power launches”, usually not a problem with the stock XD However this could be a serious problem for those that have gone FI. Wheel hop is not my major concern. For lack of a better way to explain it, I am looking for a way to better connect the gas pedal to the pavement for autocross. Bear this in mind before you proceed. The XD's “mushy” motor mounts are made for a quiet and comfortable ride. Should you use this procedure you will have increased NVH in the passenger compartment.

To avoid too much NVH, I have chosen to fill only the front and rear motor mounts. Besides filling the side mounts offers little benefit.

I looked for urethane motor mount inserts. I have only found one for the XD and it is bloody expensive. The urethane used here can be had for $20-$40 depending on where you get it.

Tools & Supplies:

* 14mm socket wrench
* 14mm combination wrench
* Exacto knife
* duct tape
* oil drain pan, dishpan, etc...
* kitty litter, oil dry, sand etc...
* liquid urethane
(I used 80A liquid urethane: P/N:
8644K11 from McMaster Carr)
* MEK (methyl ethyl ketone)
* (4) jack stands
* hydraulic jack

Estimated time:

* 1-2 hours to complete
* 2 days for urethane to cure


1) Jack car up and support with jack stands. Car must be high enough for you to easily get to the rear engine mount.

2) Remove rear engine mount (part number 21930R in attached image)
* Remove bolt number 21920 and nut 1339GB
* Remove the three bolts holding the mount to the sub-frame

3) Remove front engine mount (part number 21840) using same procedure described for rear mount.

NOTE: it is not required to support the engine when removing these mounts. The engine's weight is supported entirely by the upper side mounts (P/N: 21670 & 21930R).

user posted image

Removed mounts:
user posted image

4) The motor mounts have flashing between the voids. To get good fill with the urethane, use a sharp Exacto knife to cut this flashing out.

Cut out the flashing:
user posted image

5) Clean the rubber in the mounts using MEK (methyl ethyl ketone).
MEK is available at most hardware stores.

Flashing removed:
user posted image

6) Using duct tape, or similar, tape one side of the motor mount. Try to seal as good as you can to prevent the urethane from leaking once you have poured it.

Taped mounts:
user posted image

7) Put kitty litter in a pan, and set motor mounts in it, tape side down. The kitty litter allows you to level the motor mounts in the pan and will absorb any urethane that may leak past the duct tape.

Here kitty kitty:
user posted image

8) Mix urethane per manufacturer's instructions and pour into the motor mounts.

1lb 80A liquid urethane kit:
user posted image

Filled mounts:
user posted image

9) After a few hours you can remove the motor mounts from the “litter box” and remove the duct tape. However, you need to wait for at least 2 days for the urethane to cure to 80%-90% of its full strength. I would not put the mounts back into the car until 2 days have passed. By the way, the urethane reaches full strength after 7 days.

Finished product:
user posted image

user posted image

Thank you for reading. I hope that you find this DIY useful. Happy motoring! - toecutter
Discuss this DIY in more detail here.