Engine Mount Dissection

[roguetoaster]

Thought some of you might enjoy seeing what's inside of the stock hydraulic mounts. Total fluid capacity seems to be about 1/4 cup.

Only did this when I replaced my mounts today with fresh ones when trying to nail down a vibration issue.

These mounts were intact when pulled from the car, and had not exhibited any signs of fluid leakage (I drilled the hole to check for fluid/relieve pressure before cutting). They were about 1/2" shorter than the new mounts, and were about 7 years old. No pics of the new E30 mounts, but we know what they look like.

From the looks of it, the lower is a reservoir and has a diaphragm with a fluid passage in the aluminum.







Also wanted to do a quick comparison between 11811137076, the E30 M42 mount, and 11811141377, the E36 M42/4 mount. E36 mount is the new one. The E36 mount will only fit if one were to grind off the locating tab as it sits too far from the mount stud.

[TobyB]

Neat- thanks for that.
I'd always wondered what they were up to in there.

t

[Gkwan]

Thanks for sharing!

[fresh_TD]

Good info here!

[jaredmac11]

Does quality pay here? Ive seen a variety of prices in hydraulic mounts. Which did you put in? Id be interested to hear your before/after thoughts.

[ForcedFirebird]

I always swapped in e28 m5 mounts. Same dowel location, same threaded rod offset, but mush more solid and longer lasting.

[roguetoaster]

Quality totally pays for a street car. The mounts that I took out were BMW parts, were 7 years old (I drive like an idiot) and still had not failed, but were clearly on the way to doing so. The ones I put in were BMW parts, granted, they are ~$80 per mount, and I hope to get the same sort of longevity. In the case of these engine mounts I wouldn't go aftermarket.

The new mounts certainly seem to have reduced vibration (especially between 3500-5000), but they did not solve the problem completely. IMO the E28 mounts are a bit too harsh for a daily and do seem to endanger the subframe slightly. Perhaps the non-HD E28 mounts would be better. Further, E28 mounts have studs that are overly long, making install slightly more difficult on the passenger side, you also have to trim the alignment tab prior to install, which must serve some purpose.

[ForcedFirebird]

Yes, they are much stiffer, specially with the m42 rattle trap. Haven't had any complaints about them, but have with UHMW/Poly where they asked for stock back after some driving. Even though they are significantly higher in cost, the OEM mounts are far superior to aftermarket.

[jaredmac11]

Quality totally pays for a street car. The mounts that I took out were BMW parts, were 7 years old (I drive like an idiot) and still had not failed, but were clearly on the way to doing so. The ones I put in were BMW parts, granted, they are ~$80 per mount, and I hope to get the same sort of longevity. In the case of these engine mounts I wouldn't go aftermarket.

The new mounts certainly seem to have reduced vibration (especially between 3500-5000), but they did not solve the problem completely. IMO the E28 mounts are a bit too harsh for a daily and do seem to endanger the subframe slightly. Perhaps the non-HD E28 mounts would be better. Further, E28 mounts have studs that are overly long, making install slightly more difficult on the passenger side, you also have to trim the alignment tab prior to install, which must serve some purpose.

Very helpful. I was hoping to target quality aftermarket ones because $80 a piece felt ridiculous and I wasnt sure how much of that was just a BMW part.

[roguetoaster]

Unless something has changed, the mounts out there that are stock M42 fitment are made by Hamburg or MTC. Neither of those brands usually makes great parts. Yes, some will be fine, but as they are normally more than half of the price of the OE ones I'd rather pay up now than do the work again in less than half the time the more expensive ones ought to last.

[varg]

I didn't find the E28 mounts too stiff or harsh with my M42. As a matter of fact it still rocked over enough to bang my wastegate actuator against the wheel well when I did an enthusiastic clutch dump, so they weren't stiff enough. YMMV, I also daily drive and road trip my car with solid plastic bushings and stiffer springs than most people's track cars.

m42 rattle trap.

Damn straight

[TobyB]

Yes, but most of us don't have the wastegate, see...

heh

t