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#1
01-06-2014, 08:28 AM
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W123 urethane or silicone reinforced motor mount?
I have a pair of Lemforder motor mounts due in from Pelican any day now. I've also been reading threads regarding reinforcing the motor mounts with urethane as a back-up for the inevitable (?) collapse.
Homemade Polyurethane Engine Mounts - bushings Poking around for some shore 30 urethane, I ran across this offering. You can get a shore 30A material in silicone or urethane. Utrecht Just in case the above doesn't work, here's the silicone: Save On Discount Smooth-On OOMOO 30 Silicone Rubber Compound Mix, Shore 30A Hardness, 6 hr Cure & More at Utrecht Here's the urethane: Save On Discount Smooth-On Reoflex 30 Urethane Mold Rubber Mix, Shore 30A Hardness, No Degassing & More at Utrecht Is Flexane a brand of urethane? Thanks! - Neil
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- Neil '83 W123 (Ol' Yeller) '82 HP 34C 
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#2
01-06-2014, 10:29 AM
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Ir appears that the urethane product would work. Since it is described as a "smooth on" product for making molds of items, I would take that to mean that it is high viscosity, which would probably be a good thing. The stuff I used was very thin and therefore prone to leaking during the setup process. It also sets up quickly which is also a good thing. Mine took 24 hours to fully cure.
If I had more mounts to fill I'd give it a shot.
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#3
10-26-2016, 10:38 PM
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I am thinking of doing this also. It would be nice to get a bit more life out of the motor mounts.
I found a 30 thickness kit here for about $35 with shipping: Polyurethane Casting Resins, Rtv Silicone Rubber and Mold Making Supplies Has anyone else done this, and if so how much extra longevity have you gotten? Also, can you just pour it into the existing mount? I am planning to use Lemfoerder. Thanks, Dkr.
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#4
10-26-2016, 10:54 PM
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Quote:
Here's a link - http://www.peachparts.com/shopforum/diesel-discussion/308791-380sl-diesel-conversion-project-22.html#post3061724 I used Meyle only because the residual "flashing" from manufacturing left an almost perfect reservoir for the urethane pour. If you use another brand you'll need to figure out a way to retain the urethane (note the "hole" in the Febi one) 
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#5
10-27-2016, 12:04 AM
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Ok, that's a good tip.
When I check the eBay listings for Meyle, they show the hole as well. I wonder if the Meyle motor mounts are uniform. Mach4: do you have an advice on making the cylindrical plug for the mold? Keep in mind I don't have an entire machine shop in my garage. How difficult was the transmission mount to do? I might add that onto the project if I am getting the urethane. Dkr.
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#7
10-27-2016, 01:07 AM
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Quote:
How difficult was the transmission mount to do? I might add that onto the project if I am getting the urethane. [/QUOTE] You can use pretty much anything that is cylindrical and fits in the hole in the mount. I used a ram from a 1 ton bottle jack that was left over from making an injector pop tester. When I made my first set of mounts out of the hard urethane I filled the entire mount. Urethane is actually pretty machinable, so I just drilled the hole. Drill a pilot hole through the top, then flip over and drill to size from the bottom. The transmission mount was dirt simple. It's been a long time but I think I used duct tape to seal off the cavity. I filled my trans mount with the hard urethane and it created a harsh vibration at around 1700 rpm. I sold it to a forum member who wanted a performance "solid" mount and I didn't bother filling the replacement mount. I personally don't think it's necessary as the engine/trans assembly is supported at three points with the two engine mounts carrying almost all the weight and there's no real downside to a collapsed trans mount compared to the engine mounts. The two sets of Meyle mounts I used both had the flashing covering the "open ends" of the mount making it perfect for a pour. It was just thin flashing so it's entirely possible that it was a "defect" which has subsequently been "corrected" or possibly torn out before shipment. I recall one of mine was torn a bit and I just used some blue masking tape to seal it up for the pour. Make sure you post pictures of your process to update the data for the follow on members.
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#8
10-27-2016, 12:53 PM
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I just bought motor mounts and am planning to buy the urethane today.
Which product did you buy from Reynolds? These two look the closest -- one is 35 weight, the other is 40. Buy Brush-On® Series "Brushable" Polyurethane Rubber Compounds from Reynolds Advanced Materials Buy EZ-Mix® 40 Brushable Urethane Rubber Compound from Reynolds Advanced Materials Dkr.
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#9
10-27-2016, 01:16 PM
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It looks like their products have been renamed since I did mine. Looking through the list, if I were to buy today I would get the VytaFlex 30. Based on the specifications, it looks identical to what I got. The Shore hardness, color, pot life and cure are all the same, and the stated application (molding concrete) would be congruent - I wouldn't expect there to be a stated application for "filling motor mounts"
 Hope that helps.
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#11
10-27-2016, 01:38 PM
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I should add, if you use a rod of some sort to mold the bolt hole, make sure you coat it with a mold release and remove it as soon as the urethane sets not after it cures. Urethane is a good glue and you might not get it out. Silicone grease is what most use.
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#12
10-27-2016, 04:01 PM
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I used 5/8" heater hose for the hole support and filled w/ PL1 polyurethane gutter caulk (Home Depot) as many "mount filler guys" do (Google Images), and cured >6 months on all mounts I filled so far. Some mounts later sunk from usage so that the heater hose was poking out, so I just peeled the hose out. That hose collapsed inward during use, so had to force the allen tool past it to loosen the top bolt.
Whatever you use, you should add structural support underneath. I recently added 3/16" steel plate under those in my 1985 (during my hydraulic mount test saga, search). If not, the thin sheet metal underneath will crack as the filler starts applying force to it (my 1984, see post). The polyurethane was still quite soft. I could depress it with my finger. It was surely doing something since it had the shape of the sheet metal depression beneath the mount. It is probably working harder w/ the flat steel plate now pressing it in. You will probably notice the engine a bit buzzier in the cabin, with more noises from anything loose, but not objectionable in my 1984. My 1985 is quite shaky now at 1500 rpm with the filled mounts on backer plates. But it had filled mounts before and was quiet. Seems I changed the engine somehow when trying the Corvette hydraulic mounts (which may be solid rubber). It was terrible with them, but still half-terrible when switched back. I did have to lift the engine to the max to get the Corvette's in, and stretched hoses slightly before I noticed to unbolt them. The lift pump inlet filter popped off the hose while wrenching, so suspect I might have gotten debris in the lift pump or such. That will be my next try when my son returns that car (have spare lift pump plus rebuild kit). I did work to purge all air from the fueling system. I cracked each injector supply tube until it dribbled and each one affected the engine about the same.
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1984 & 1985 CA 300D's 1964 & 65 Mopar's - Valiant, Dart, Newport 1996 & 2002 Chrysler minivans Last edited by BillGrissom; 10-27-2016 at 04:12 PM.
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#13
10-27-2016, 08:11 PM
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Call Smooth-On for advice on which rubber to use. They are helpful. That's who makes Vytaflex and Brush-On and many other varieties of both polyurethane and silicone. I use a lot of their stuff in my sculpture foundry.
The final hardness doesn't reflect the viscosity. Brush-On has a thick viscosity, even in the soft versions such as 30 and 40; whereas Reo-Flex, for example, is almost like motor oil in the 30 aqnd 40 varieties. Richard
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#14
10-27-2016, 11:53 PM
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Quote:
Poly-filled motor mounts - problems I think it's disingenuous to declare that filling the mounts will automatically destroy the car when your post clearly shows that the frame was damaged and definitely poorly repaired before you installed the mounts, then the rusty, crappy sheetmetal broke, which should be no surprise to anyone looking at the pictures. You then say that you had no problem with the same mounts on a different (presumably undamaged) car. I've had no problems with mine and have yet to see anyone else report any problems, other than excessive vibration with a stiffer filling. I think your dire warning should rather be: Inspect your frame for damage, rust, and shoddy repairs before installing filled mounts. Install an extra plate for good measure, but it's probably not necessary. It's enough already, I'm tired of hearing the warning without the backstory that makes it obvious that it's probably much ado about nothing. -Rog
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#15
10-28-2016, 10:08 PM
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So, I received both the urethane and the Meyle motor mounts today. The Meyle motor mounts are solid rubber despite the picture on the various websites. So, I don't need to find a way to seal it when I pour the mold. I bought 1 foot of 3/8" heater hose, cut in half and then cut up the end-points to make it fit through by the hole by itself.
I'll post some pics once I pour. Dkr.
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