More on Motor Mounts - PeachParts Mercedes-Benz Forum

NoSparkNeeded · #1 11-05-2013, 07:33 PM

These are a couple things I learned today whilst looking up other things.
I previously stated that I was missing a "splash" shield on top of my right motor mount on my wife's 84 300SD. I guess it really isn't "missing", it was never there if I'm interpreting the FSM correctly. On page 22-211 there is
a little chart. It says there is a shield only on the left. It also says the left
mount has 2 blue dots, the right has 1. I think the dots relate to hardness. It also lists 2 different part numbers for the mounts. Now this is
listed as a 126.120. I don't know if that refers exactly to our car or not.
All this probably doesn't functionally mean much, I just thought it was curious.

Diesel911 · #2 11-05-2013, 10:25 PM

Quote:

Originally Posted by NoSparkNeeded

These are a couple things I learned today whilst looking up other things.
I previously stated that I was missing a "splash" shield on top of my right motor mount on my wife's 84 300SD. I guess it really isn't "missing", it was never there if I'm interpreting the FSM correctly. On page 22-211 there is
a little chart. It says there is a shield only on the left. It also says the left
mount has 2 blue dots, the right has 1. I think the dots relate to hardness. It also lists 2 different part numbers for the mounts. Now this is
listed as a 126.120. I don't know if that refers exactly to our car or not.
All this probably doesn't functionally mean much, I just thought it was curious.

126.120 is most likely the Chassis type; W126.120. My W123 is a W123.133.
I think you are going to find that the only Company that makes the Motor Mount with the green dot part number is going to be Febi or Myele. And, that means there is a high chance that they would be made in China or some other area on that side of the World.

TnBob · #3 11-05-2013, 11:03 PM

Have you considered making your own from urethane ?

shadetree77 · #4 11-05-2013, 11:30 PM

i have some very old NOS mounts that have the different part numbers and dots. they don't
make them in different hardness anymore. get some lemförder mounts; they are the same ones that the dealer is selling, except they have the mercedes star ground off
TnBob, how do you make them out of urethane?

NoSparkNeeded · #5 11-06-2013, 12:32 AM

I have 2 new Lemforders to go in this weekend. I just happened to run across the new info today and thought others would be interested about the info in the FSM as I had not seen any mention of such a thing.

mach4 · #6 11-06-2013, 10:08 AM

Quote:

Originally Posted by shadetree77

...how do you make them out of urethane?

It's probably not feasible to actually make your own, but you can do the next best thing, and that's to use a cheap set and fill them with urethane. The failure of the mounts is primarily due to collapse. If they are filled, they can't collapse.

Here's a link to how to do the job along with recommended mounts to use to make the job dramatically easier - 380SL Diesel Conversion Project

Before

After

NoSparkNeeded · #7 11-06-2013, 04:30 PM

Filling them like that would make them last virtually forever I'd think. Do
you think it transmits enough extra vibration to be felt at any significant
level?
I have a Jaguar XJS V12 that I replaced all the rubber bushings with urethane. Trans, Motor, steering, shocks etc. Luckily the aftermarket
had all those for sale at a reasonable price.
The GOOD. It handles so much better and more precisely due to the rack
being now mounted in urethane. At least now they will last. Almost
all old bushings had turned to GOO. No kidding, goo.
The BAD. Urethane on the Jag does increase noise and vibration to a very small extent. The V12 is so quiet that you can hear any extra noise. The increase isn't much, but I could hear and feel it at first, but after that first hour I no longer notice it. I doubt anyone would notice unless they had a fast before and after as I did.

whunter · #8 11-06-2013, 05:18 PM

Quote:

Originally Posted by NoSparkNeeded

These are a couple things I learned today whilst looking up other things.
I previously stated that I was missing a "splash" shield on top of my right motor mount on my wife's 84 300SD. I guess it really isn't "missing", it was never there if I'm interpreting the FSM correctly. On page 22-211 there is
a little chart. It says there is a shield only on the left. It also says the left
mount has 2 blue dots, the right has 1. I think the dots relate to hardness. It also lists 2 different part numbers for the mounts. Now this is
listed as a 126.120. I don't know if that refers exactly to our car or not.
All this probably doesn't functionally mean much, I just thought it was curious.

The engine mounts superseded to a single part number for both.

126.120 = Chassis W126 Model 300SD

.

Diesel911 · #9 11-06-2013, 06:06 PM

Quote:

Originally Posted by NoSparkNeeded

Filling them like that would make them last virtually forever I'd think. Do
you think it transmits enough extra vibration to be felt at any significant
level?
I have a Jaguar XJS V12 that I replaced all the rubber bushings with urethane. Trans, Motor, steering, shocks etc. Luckily the aftermarket
had all those for sale at a reasonable price.
The GOOD. It handles so much better and more precisely due to the rack
being now mounted in urethane. At least now they will last. Almost
all old bushings had turned to GOO. No kidding, goo.
The BAD. Urethane on the Jag does increase noise and vibration to a very small extent. The V12 is so quiet that you can hear any extra noise. The increase isn't much, but I could hear and feel it at first, but after that first hour I no longer notice it. I doubt anyone would notice unless they had a fast before and after as I did.

Filling the Motor Mounts also stiffens them and you may feel more vibration.

mach4 · #10 11-06-2013, 08:36 PM

If you read through my build thread, you will see where I originally filled a set of mounts with Shore A 75 urethane which turned out to be way too hard. It worked great, but transmitted a whole lot of vibration at idle - not unlike solid mounts. It took awhile to figure out what was going on as I worked through other possibilities - injectors, timing, fuel, damper and so on. I finally replaced the filled mounts with stock mounts as a test and the idle vibration went away completely. Knowing that it was the filled mounts, I did another set of mounts with very soft Shore A 30 urethane, and the vibration levels were virtually indistinguishable from unfilled ones.

The specific symptoms were bad vibration at idle to about 1000 rpm and then a secondary vibration at 1700-2000 rpm. At other times, it was very smooth. The secondary vibration turned out to be from the filled transmission mount. That wasn't nearly as critical, so I just replaced it with an unfilled mount. Ended up selling the filled mount to a forum member that wanted a stiffer transmission mount for performance reasons. He reported the same vibration, but was happy with the performance gains.

A quick side note - in the week or so that I had the unfilled mounts in the car, the mounts collapsed 1/4 inch.

I've been running filled mounts for 34000 miles now with no measurable collapse.

Vstech and Thayer, mods on this forum, have both driven the car so they can independently verify whether there is any adverse vibration levels.

LandYaghtLover · #11 11-06-2013, 08:46 PM

Great read! I have two OEM mounts coming. This will be my third install in two years! I think I will do as above!

gear-head · #12 12-14-2013, 03:35 PM

Mach4, care to share where do you get this "Shore A 75 urethane", please?

mach4 · #13 12-14-2013, 04:38 PM

Quote:

Originally Posted by gear-head

Mach4, care to share where do you get this "Shore A 75 urethane", please?

The Shore A 75 Urethane should only be used if you are trying to get extremely firm mounts. Using this urethane will give you close to solid mount kind of performance. Very high vibration levels particularly at idle. If this is what you're looking for, AeroMarine Products is a good source.

The Shore A 30 Urethane that I have used successfully and recommend can be sourced through Reynolds Advanced Materials. It appears that they have a "next generation" product called ReoFlex which is available in Shore A 20, 30, 40, 50 and 60 hardnesses. While this isn't the actual product I used, it's the one that replaced the one I used. It's what I would order today if I were to create another set of mounts.

Also I recommend the Meyle mounts. They may not be the best mounts available, but the way the flashing remains from their manufacturing process leaves an almost perfect void into which you can pour your urethane. With other mounts there is no flashing and you'll need to figure out how to seal up the "side" of the mounts to retain the urethane. Since your mounts can't collapse, you can use slightly inferior mounts to start with.

For those that have or are going to make a pop tester, the ram on a 2 ton bottle jack that you'll remove and throw away, is the perfect size to shove in the bolt hole to seal that up and cast a nice bolt hole. Cut in half - one for each mount.

See this link for more details - 380SL Diesel Conversion Project

gear-head · #14 12-17-2013, 02:55 AM

Quote:

Originally Posted by mach4

Also I recommend the Meyle mounts... the way the flashing remains from their manufacturing process leaves an almost perfect void into which you can pour your urethane. With other mounts there is no flashing and you'll need to figure out how to seal up the "side" of the mounts....

...the ram on a 2 ton bottle jack that you'll remove and throw away, is the perfect size to shove in the bolt hole to seal that up and cast a nice bolt hole. Cut in half - one for each mount.

See this link for more details - 380SL Diesel Conversion Project

Fascinating information, I do appreciate all that. So I'm curious if by any chance you might know, off hand, if any other "cheap" brands that may have similar manufacturing process/design leaving similar flashing? Or a source for said brand? Second question, any / all brand(s) of 2 ton bottle jack has the same size ram?

Did you use One Step Release Agent & Sealer from Reynolds, or is there another product you have used/would recommend, please?

tia, best regards

tia, best regards

mach4 · #15 12-17-2013, 02:40 PM

Quote:

Originally Posted by gear-head

So I'm curious if by any chance you might know, off hand, if any other "cheap" brands that may have similar manufacturing process/design leaving similar flashing? Or a source for said brand? Second question, any / all brand(s) of 2 ton bottle jack has the same size ram?

Did you use One Step Release Agent & Sealer from Reynolds, or is there another product you have used/would recommend, please?

I have no knowledge of other brands that may or may not have sufficient flashing covering the open end of the mount. You can often tell from the pictures in the shopping cart whether this is the case.

I think most bottle jacks are built on the same formula, possibly by the same manufacturer and marketed under lots of brands. I only bought the one I used for my pop tester.

As far as mold release, you only need that if you're going to be making multiple filler pucks from one mount. Urethane is a good adhesive, but I found that after being in the car for a bit, they just pop out.

Here's what one looks like removed from the mount.