My wife's 2007 Mazda3 (50k miles) has developed an engine rattle on start-up that appears to be a failed motor mount. Since the 5-yr powertrain warranty just expired in March (figures!), looks like I'll be replacing it in the driveway. Not a big deal, it's extremely easy to get to. A quick internet search shows these are prone to failure, with some people going through several in the course of 80 or 90k. The motor mount is $95, so I'd rather not have it be a regular maintenance item.
Here's my GRM low-budget idea: fill the space that used to be occupied by magical damping oil (30% unicorn tears by volume) with Shoe Goo. Any idea whether that might work? I have seen it done to stiffen Miata diff bushings (e.g. Keith Tanner's Seven). I don't see it being dangerous, since she's already driven the car with no fluid at all in the mount. The plan would be to buy a new mount, remove the old one, and try it out. Any other materials that might work better? I have seen rubber-only aftermarket motor mounts, but at $300 a pop, it's a little more than I would want to spend.
Nice! They ain't exactly giving it away, though. We have been messing around with casting compounds at work (for cold-flow testing turbine components), I think we might have some flexible stuff left over.
There is also a 3M window sealant that comes in a tube that can be found at local home improvement stores that has been used as well. There is a really good writeup on filling RX-8 motor mounts that is probably particularly relevant here: http://www.rx8club.com/showthread.php?t=212403
Keep reading on my site - it didn't work 
Does Energy have an inexpensive poly version? If not, why not ask them about making one?
If it were me, I would fill it up with Dow Corning RTV-3145.
Can you give me the link that discusses the failures?
My wife has an 08 Mazda3 wagon, they call it a hatch, but its a wagon. We have 82k miles on it but haven't noticed the rattle yet.
I am not familiar with how these mounts work, do you have a photo?
I have used the RTV (or silicone) cure with some success on other motor mounts, but it really depends on the configuration.
Are there any aftermarket sources? If the Mazda part is $95 you might get a comparable aftermarket for less than half that. If you do something non-oem style (RTV, silicone, shoo goo, etc) that ends up stiffer you are going to end up with more vibration transferred to the passenger compartment.
Mazdeuce - Thanks for the RX8 link! That is exactly what I was thinking. The 60 durometer option sounds pretty good for the application.
Keith - Yikes, I had read through your whole build a while ago, but forgot that the Shoe Goo failed. Energy Suspension doesn't list any parts for the Mazda3 (kind of surprising, IMO).
We have some 45 durometer pourable silicon (V-340 from Freeman Supply) at work. It's pretty soft, but that might be good for a daily driver. Thoughts?
Octavious - My wife's car is also the wagon.
Couple links:http://www.mazda3forums.com/index.php?topic=119411.0
http://www.mazda3forums.com/index.php?topic=185198.0
ShadowSix - Link to Finish Line in first post has a pic of the mount.
Oh, and here's someone with the same idea: http://www.mazda3forums.com/index.php?topic=202345
i like to use 3M product 08609. you can get it anywhere.
belteshazzar wrote:
i like to use 3M product 08609. you can get it anywhere.
oh another product to add to my must try list. thanks.
this product has not failed me yet. the oldest mount is going on 7 years now.
Hell I might even try it on my brothers Mazda 3 motor mount while I am at it.
because it's somewhat expensive, i try to line up four or five things i want to do with it before i crack open a tube.
Elsmere
New Reader
5/9/12 4:34 p.m.
I will second or third that the 3m window weld urethane works great. I filled the gaps in the motor mounts on my dad's neon about 50k ago and the motor still isnt flopping around.
mazdeuce wrote:
Pourable urethane.
http://www.mcmaster.com/#liquid-urethane/=hgjwg8
Do you think this stuff could be used in suspension bushings? (i.e.: set up outer and inner shells and pour extra hard urethane in). Might be too soft, but could solve a little problem for me.
If you search on the lemons forums (I think) somebody talks about making blanks and then working it very slowly with woodworking tools on a lathe. I think the biggest issue in pouring a bushing is keeping things centered. I haven't used it yet myself, it's on my list of stuff to do, so don't trust anything I say, but if you do try it, do it somewhere that a failure won't end your day too badly. And make sure it's not in tension in any way. Probably.
If you search on the lemons forums (I think) somebody talks about making blanks and then working it very slowly with woodworking tools on a lathe. I think the biggest issue in pouring a bushing is keeping things centered. I haven't used it yet myself, it's on my list of stuff to do, so don't trust anything I say, but if you do try it, do it somewhere that a failure won't end your day too badly. And make sure it's not in tension in any way. Probably.
Interesting. I already have some delrin that I think could be used like that, but it's hard to find a lathe with a 1" thru bore that doesn't cost a mint.
In reply to Teh E36 M3:
Can you bore a hole for the sleeve first, mount the sleeve, through bolt it, then chuck the bolt in the lathe and turn the outside from there?
I've thought about doing this but I don't even have a small lathe, I was going to use a drill that had the speed controlled by a dimmer switch. I only got as far as setting up the dimmer to control the drill. That part works anyway.
i've had good luck with 3M window weld in the past (both mr2 and the neon acr)
Is this the part you need?
Rock Auto $54.79
Quick update: Pulled the passenger motor mount out on Saturday and it looked fine. Looked underneath while I was taking off the plastic under tray (or whatever it's called) and the transmission mount looks fine, too. Didn't have time to remove the battery/intake/whatever else to look at the driver's side mount, but that's on the agenda the next time we have a nice day.
As a sweet (not!) bonus, I found out the place I have been taking the car for oil changes thinks that two bolts holding on that under tray, plus a zip tie where they had broken a plastic tab, was totally sufficient. Looks like I'm back to doing my own oil changes on that car. Slightly in their defense, the mounting design for that tray is horrific. All of the bolts had seized and the heads broke off when I went to remove them. The whole metal tab with captive nut in splash zone design could have used another look.
