Ahhh, but how do you know they are what they claim??
Again, I am not trying to be an A$$ here, but unless we get someone to cut open an MN12 performance mount, we will never really know the whole story or if they are hollow like the rest.
My story started with an 89 SC I used to own. Both original mounts were shot so I ponied out some big $$ ching ching for replacement hydraulic mounts. I was lucky in the way that for installation I had access to a lift, which made install a little easier. But, I would say that within 3 months, the drivers side mount was broken again. So I brought those back and got my $$ back and went to Twin "B" Auto Parts (I lived in VA Beach in 1998). I remember someone posting on the SCCOA that a certain year Tbird used solid mounts on one side and hydraulic on the other (Ford's attempt to fix their huge screw up). I went to Twin B and sure enough, they had the solid rubber mounts for all of $25.00 each. This was much better than the $65.00 each for the hydraulics at the time. I got the solids, put them in a week later, and never had another problem till I got rid of that car a year later (stupid me traded it in on a, you guessed it, a 99 Mustang GT).
I guess the morale of this story is that do we ever know exactly what we are getting? I wonder if you cut the $40.00 mounts and checked them out, would you find them to be hollow as well?
I think the whole problem with the "hydraulic" mounts is this...they are "hydraulic"!! Sounds simple and stupid right? Think of it this way, after my tour of duty in our great United States NAVY (no sarchasm, I loved it, but screwed up my back and could not stay in.. anyways) I learned quite a bit about hydraulics and fluid dynamics. Look at the shape of the mount before installation, looks good right? Real uniform, no creases or obvious flaws, etc. Take those two "hydraulic" mounts and install them. See how they crush sort of under the weight of the engine? They deform quite a bit don't they, at least mine did. So, here is where the hydraulics part comes in. What happens to fluid under pressure? You cannot compress a fluid as it has a definite volume and takes up a definite amount of space right (some may not agree, but that is the principle of hydraulics). Now that the weight of the engine is trying to crush these mounts, the fluid inside the mounts is now pressurized. The fluid inside is going to try and find any way out of the mount that it can. A simple crack in the inside of the mount, or a tear on the inside can start the process. Add to the equation the engines natural tendency to twist under accell and descel, and the mount is stressed incredibly. I would think that the fluid filled mounts are under much more stress than the solid or "hollow" mounts are because the fluid is always fighting to get out right? Add another factor of abuse and clutch dumping, and heat/elements, and utter lack of movement limitation (i.e. torque strap) and it is no wonder the hydraulic mounts fail.
So, there is my theory, see what you think, I am going to go out to my garage and see if these are hollow and if so, oh well.
