Upper Engine Mount

kaddo · Post by **kaddo** » 25 Nov 2009, 13:21

Yep, mine broke, too.
I see many posts on replacing that rubber part,
but did any of you try filling it up with silicone?

I keep thinking... what can possibly happen?
Maybe there is something I miss completely.

Curious to hear comments, I will appreciate your help.

Post by **polskamafia mjl** » 25 Nov 2009, 16:41

The rubber does a surprisingly good job of dissipating engine vibrations, in addition wouldn't it be incredibly hard to fill it up with silicone??

kaddo · Post by **kaddo** » 25 Nov 2009, 17:41

polskamafia mjl wrote:The rubber does a surprisingly good job of dissipating engine vibrations, in addition wouldn't it be incredibly hard to fill it up with silicone??

Thanks for your interest, Polish Mafia.

Hard? Not at all. I'll have access to both sides of the broken rubber and that probably without having to undo the assembly.
All I need to do is pump some silicone in by using a caulking gun.

Again, my main concern was not to allow, or disallow a damaging movement on the engine.

As you may know, the rubber part resembles a hockey puck.
Like a tiny bicycle wheel with its hub connected to the rim with only two spokes. The rest is air, which indicates to me that the manufacturer was concerned with limiting the up-and-down movement and only allowing some to the front-to-back. Those spokes became separated from the rim and now the front-to-back has zero resistance, but the up-and-down is unchanged.

My idea is that I could repair the damage and obtain a similar effect by simply injecting silicone between those two spokes.
It will still offer some give, but will hold the spokes in their original place, and therefore let them continue do the intended job.

I was mostly concerned with not giving too much rigidity, but after reading about the use of those solid Polyurethane bushing being an accepted replacement, I figure silicone may be an even more appropriated material. Am I making any sense, what you think?

Post by **polskamafia mjl** » 25 Nov 2009, 20:23

That does make a lot of sense. I would however like to point out that a lot of people don't recommend the polyurethane mount from IPD because they are too rigid and increase engine vibrations in the cabin. However, your method is extrememely interesting. If you do do it, make a write up and then get back to us about your results as far as feeling vibrations in the cabin. If the silicone method turns out to be as good or better than the OEM rubber bushing than you will have given us a new option when considering a replacement part for the motor mount.

kaddo · Post by **kaddo** » 25 Nov 2009, 23:11

polskamafia mjl wrote:That does make a lot of sense. I would however like to point out that a lot of people don't recommend the polyurethane mount from IPD because they are too rigid and increase engine vibrations in the cabin. However, your method is extrememely interesting. If you do do it, make a write up and then get back to us about your results as far as feeling vibrations in the cabin. If the silicone method turns out to be as good or better than the OEM rubber bushing than you will have given us a new option when considering a replacement part for the motor mount.

Thanks for your encouraging comment, polskamafia!
If successful, I will surely contribute by posting details of my "silicone job"

.

Meanwhile, I came up with a better alternative, I think.
I must take a closer look at that rubber mount and this time measure the two empty spaces around the hub.
Then, I will find a rubber hose with the OD a bit larger than that and by collapsing it, I will try to push it through, first from one side, then back from the other.
Such loop will re-center the hub and provide the necessary, but not excessive resistance to the horizontal movement of the engine.
I can't see why this shouldn't work, can you?

I will check tomorrow the local hardware store for their stock on hoses and test the idea. When all done, I will post a photo.

Post by **Ozark Lee** » 26 Nov 2009, 00:50

kaddo,

Give it a shot, I like the way both you and polskamafia think, a very reasoned and logical discussion.

I really don't think it will work since the loads on the bushing are lateral and the bonding power (how much it acts like a glue to hold things together) of silicone, even in laboratory conditions, sucks. Under the hood of a car is not laboratory conditions by any stretch of the imagination unless you do climate change research for a living.

Silicone is very good under compression, however, and if you fill the vertical voids in the mount the silicone may actually limit the horizontal (torque) travel and tame things down and provide a cheap cure for a problem that we all face with our 850s.

At the end of the day you have nothing to lose except a tube of silicone. If it doesn't work it will have really created no new problems for you - as you change out the bushing for the new replacement.

Let us know.

...Lee

kaddo · Post by **kaddo** » 26 Nov 2009, 06:14

Ozark Lee wrote:kaddo,
I really don't think it will work since the loads on the bushing are lateral and the bonding power (how much it acts like a glue to hold things together) of silicone, even in laboratory conditions, sucks.................
...........................
Silicone is very good under compression, however, and if you fill the vertical voids in the mount the silicone may actually limit the horizontal (torque) travel and tame things down
...Lee

Your input is always valued, Lee.
Yes, silicone won't be of a much help if used as adhesive.
Knowing it, here I only rely on its compression characteristics.
Once cured, I think the silicone will become one with the surrounding rubber not by gluing, but by using it as mold.
Being mostly concerned with too much resistance to the lateral movement, is that I thought of using the rubber hose method, in stead.
What's your opinion on that?

kaddo · Post by **kaddo** » 26 Nov 2009, 09:10

The "silicone implant" is done.
I kept tossing in my head between that and the rubber hose method.
Decided to go for the silicone simply because it was... simpler.
Will let it fully cure till tomorrow and then see how the engine likes it.
I don't expect anything to go terribly wrong, but we all know that Murphy never sleeps.

Post by **RobTheModd** » 26 Nov 2009, 13:05

Just wondering.
Which is best for the mount to replace. And get minimal vibration?

kaddo · Post by **kaddo** » 26 Nov 2009, 13:21

RobTheModd wrote:Just wondering.
Which is best for the mount to replace. And get minimal vibration?

Not sure I understand your question, Rob.
Please, rephrase.