OK. We have all heard of using 3M Window Weld in our engine mounts, and Energy Suspensions motor mount inserts. You have probably also heard about how hard those products are and that they are not daily driver friendly and some people even remove them because they say the vibration and noise just isn't worth it.

So I did a little homework to find out what grade of urethane would be appropriate. Here is a hardness scale :



Based on this scale, the ES inserts are in the ballpark of 85-90A. On a sidenote, a bowling ball is about 100A.

So based on the some of the info I found on the net (the nissan guys have done a lot of homework on this), 60A seemed to be the best bet. I figured that it would stop movement without rattling my teeth out.

Thanks again to the nissan guys, I found that Mcmaster-carr ( www.mcmaster-carr.com ) carries urethane casting compound in various hardnesses. They are as follows :

Flexible Urethane, Shore 60A - 8644K24
Flexible Urethane, Shore 80A - 8644K11
Flexible Urethane, Shore 94A - 8644K18

There are other places that carry urethane casting compound such as www.smooth-on.com , but when I called their tech support, they were unsure if it could deal with the temps that it might see in the engine bay. So I went with mcmaster-carr since the nissan folks had been successful with it.

To start, I couldn't deal with the downtime of removing my mounts and filling them and I also wanted to make sure that I started with a good mount instead of patching a broken one, so I picked up a set of new mounts, sides and rear. My car has > 120k, so it was time anyways. Based on what I've read from others on the ES inserts, I decided to just fill the 2 side mounts and not touch the rear mount.

Here are the 2 new mounts :


The first thing that you have to do is tape up the mounts to prevent the urethane from leaking out. I used duct tape. Why duct tape? Because it is waterproof, so it should minimize any leakage. The urethane is a little thicker than syrup, but can still ooze out if you do a poor job taping them up, and then you have a mess on your hands. I suggest that you place them in a disposable *leakproof* container. The mom/wife/girlfriend/whoever won't like it if you spill this stuff.


Here is the 60A urethane. It is like epoxy and comes in 2 parts. It comes in exactly the right ratio, so just dump the little container into the big container and mix well for at least 2 minutes. It even comes with a mixing stick. Once you join these 2 liquids, there is no going back. This stuff sets in about 15 minutes, so that is how long you have to work with it before it gels up. This is why you tape the mounts first.


Here are the mounts after I have poured the urethane into them. These 2 mounts only required roughly *HALF* of the urethane, so you could split the cost with a buddy and do them for 2 cars at once.


Now we wait... How long? About 48hrs. This stuff has to cure for 2 days and DO NOT try to rush it. Also temp needs to be roughly 70deg. It was winter time, so I just turned up the heat. You will notice that in less than 8hrs, the urethane will be hard to the touch, but you still have to let it cure the entire 48hrs.

We have waited our 48hrs, and this is what they look like once the tape has been removed.


Based on the info that I read on how to properly cure polyurethane, another 4hrs at 150deg will improve their strength and durability. Well... I found out that my oven only goes down to 170F (d@mn new-fangled oven with digital controls). So I broke out the cast iron, popped it into the oven @ 170 and got the pots hot. That is a deep frying pan and its lid. Once hot, pulled them out of the oven, placed a towel in the bottom of the pan and set the mounts inside, then put the lid back on. The pots are just sitting on top of the stove now, the burner is *NOT* on. I then left and came back sometime that afternoon. Of course this rig wasn't hot for 4hrs, but it was better than nothing. Also follow directions and temperatures closely. This stuff can only handle 180F. Remember urethane is just a form of rubber and it can still melt.


Now, I'm all set and ready to go. At least that is what I thought. When I go to install the first mount, I notice that there is a pad welded onto the frame where the mount goes... Looks like it is basically like a bumpstop for the mount. Didn't know that it was there and my home-made mounts won't clear it. So I break out the die grinder w/wire-wheel attachment and start grinding on my newly made mounts. I removed about 1/4-3/8" of the polyurethane off the top of the mount. This pic shows where it was removed. You could avoid this step if you place a piece of wood or something in the mount after you tape, but before you pour the urethane.


Here is my lower driver's side mount... It has seen better days, but it does explain the *thunk* whenever I made a hard turn.



So... Initial impressions... The interior does buzz and I do get some vibration at idle. I have noticed that it is only when my idle dips below about 600 or so that there is any noticeable vibration, but when it does, it is annoying. With the radio at a moderate listening level, you can't even hear the buzzing (if there is any). Once the engine is past 1000rpm or so, there is no noticeable buzzing or anything. While driving I do notice some more feedback in the gas pedal from the engine, but I like feedback from the car.

As for handling... I love it! Car handles beautifully, goes wherever I point it. The sloppiness that I was feeling is gone. Launching is also better. I don't drag launch or anything like that, but even an aggressive take-off feels better.

For now I can live with the occassional buzz and vibration. If it starts to bother me, then I plan to pull the mounts and drill a few holes into the urethane to help make them a little more pliable.

As for what prompted me to do this, I took the car to the dyno a few weeks back for a baseline run and watched the engine as the guy at the shop reved the motor. It jiggled back and forth like it was doing the harlem shake... it was ridiculous...

Why didn't I buy aftermarket mounts? Well, they are either overpriced, don't tell you how hard they are, or both...

Anyways, this is a relatively simple and inexpensive mod. It will require some mechanical ability to actually install them. Installation time should be roughly 2hrs.

You can find an install howto here :
http://www.hazone.com/hmtrmount.htm