Dear PO: Replacing the Motor mounts 360.

Dear PO,

Original Owner, thank you for paying thousands above MSRP to import my euro. She is loved. PO(s) (prior owner), I decided to replace the motor mounts on the car today. I did it in my garage with the rear wheels on ramps. I saw when she was on a lift before that you had upgraded the motor mount to the more modern part. I commend you for that. I basically raised the rear end, took off the bottom panel and saw there were five bolts on each mount. Four that hold the mount to the body and one big bolt and nut in the center. I started by taking a 24 mm socket and 24 mm wrench that I bought at Northern tool for about 15 bucks. I put the wrench on the top of the big bolt to secure the nut. I then took the 24mm socket and put it on the bolt head on the bottom of the car. I used a cheater wrench to help me do the deed. It was tough, but I managed to get it moving. I turned and turned. The bolt fought me. It was a fine thread.. but it fought. It groaned, it creaked. But in the end I got it off. As it turns out your mechanic, Klaus, the one that used to repair tanks for the Romanian army? The one that you took the car to because he once fixed your wife's 500sl that time.. I know that a tank tread takes 300-400 ft/lb of torque to get seated... but you don't have to torque it down so much. You see with all that cranking the threads almost stripped off. Luckily I went to an ACE hardware and they had a tight thread 5/8 x 4" standard bolt and nut that worked perfect. The 24mm wrench and socket worked perfect to get it in. It only cost me 2 bucks each nut and bolt.
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.. I then went and undid the other four(4) 17mm bolts and nuts on each motor mount. They came off real easy and didn't strip.

I then took a wooden pad and placed it on my floor jack. I raised the engine juuussst enough to remove the old mounts. It went in on the side of the car to make room. I placed the pad right behind the oil drain plug on the bottom of the engine. I raised it real easy, millimeter by millimeter, always checking the water hoses. After 15 or 18mm or so, the old mount came out. I did have to stretch the bottom of the rubber to get it out. But get it out I did.

As you can see, they were very flat. But my new ones are not smushed.

I squeaked and pulled on the rubber and got the new mounts in. The key was getting the bottom rubber into the hole where it rests. Its tough to squeeze it in, but it won't hurt the mount.
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But you see I noticed something. When you had Klaus "update the motor mounts" so you could sell it and buy a GTR or M5, he skimped. You see, the new motor mounts use a different washer on the bottom. See in the diagram below the new, how it has that little raised section in the middle? Well, Klaus used the old flat type. I get it, I really do. The stupid new washer is $60 some odd bucks! The mounts were $150 a piece! I have no problem when your mechanics use an "equivalent" solution when they jury rig.

The problem is that when Klaus re-used the washer, it "smooshed" down the motor mount. In essence it compressed it wearing the mount out prematurely. Indeed the rubber itself isn't even too cracked.

Its OK. When I replaced the bolt, I put 2 5/8" spring washers above the flat washer on each side.. in essence doing what the raised potion of the new washer does when compressed down. When I put it all together and bolted it all up, it worked perfect! (100 lb/ft big bolt, i think 70 ish smaller ones. I just did it nice and tight with some thread locker on the big bolts even given the heat there) Who knew $1.00 worth of washers could have a similar effect as $120 worth of Ferrari parts. I wish he'd done this. Overall about 3 hours for both mounts. There were no more vibrations in the cabin. Heck, it even felt as smooth as my Boxster! Quieter, smoother. So nice.

So PO, with this I'll say goodbye. I'm sure I'll write you again. If you see Klaus, give him my best and tell him I hope that old mercedes Diesel holds up. There isn't anything else to do now except enjoy the car. It really is running great.

All the best,

Curt
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I want to drive it. Now.

Seriously. Exact same diameter, exact same length. Exact same nut, head, weight, etc. The only thing that is different is the threads on the bolt and the matchign nut. Which for all practical purposes is immaterial. The exact same bolt with just differences in threads. For half the price of the Ricambi part. Functionally they are identical. Seriously, it's just threads. Metric fine vs. standard fine.

Works great.

 

These motor mounts were actually pretty easy to replace. The hardest part was the large center bolt that shouldn't have been that challenging to replace.

In contrast to other cars, I'll use my 928 as a reference to which you have to drop the steering rack and a cross member and IIRC to then lift the engine off the mounts, the FCar is a breeze. If I had a lift it would have been a 1-2 hour job max. I'm just being a redneck and using ramps. At least for the 928 the book has what 6-8 hours? With bolts that break and are frozen.. 12?

Motor mounts are reported as a "high wear" item. They are close to the headers and can heat up rather easily.. but my mechanic reports he's never done a replacement on a 360. I think in my case, an inexpensive 360 that I bought knowing it needed some things, this was due to erroneous installation by a prior mechanic. Bear in mind I also owned this car now 3 years before replacing this part. It's not mission critical so to speak. Its also a relatively easy enough job that if I ever have to do it again, I won't mind doing it versus lets say replacing the oil/water intercooler below the air intake which is a much bigger PITA with tight spacing. I think this car at 13 years of age at least as reliable as the Boxster I had. It's easier to fix, and once fixed holds up just as well.

 

The second that I put them in I noticed a dramatic reduction in vibrations.

Mr. Crall,
I understand where you're coming from and respect your feedback.

However, please allow me to issue a rebuttal.

1) Metric hardware versus non-metric hardware. The dimensions of the bolt and the nut in metric and non-metric are EXACTLY the same. Down to the 0.02 millimeter. I checked with my caliper. The pitch of the thread and the locking nut perform the EXACT same function, in the EXACT same manner in both cases. It application is documented in my repair log. If the next owner (I have no intention to sell) doesn't look/doesn't care. Their problem. I have no intention to flip this car. Ever.

If the original ferrari nut trashes the bolt the way mine did.. a mechanic will just use a new set of each right? Which means a non-metric application is a moot point for the next mechanic..

2) Fit. As a 99' the original mount did NOT have a lower spacer, so you could put the bolt through the mount and just tighten it up. The newer mounts require a spacer and this evident on the install. The PO assumed the old modality and tighted to the end. Thus, the mount was overcompressed and failed.

3) Spacers. A spacer is a simple piece of metal. Nothing more, nothing less. One thick $60 piece of aluminum does the exact same thing as steel washers below it. Furthermore the contact point on the metal within the center of the motor mount is maintained with the washers that I used, it did not extend into the rubber. The mechanics of the mount, vertical forces downward and lateral forces are EXACTLY the same in both configurations. Which is why..

At a year out.. its flawless performing as expected and designed. Inspections in 3, 6, and 9 month intervals show no degredation of the mount, no overcompression of the rubber, and no issues with bolt placement or function.

In essence, the repair does EXACTLY the same as the OEM configuration.

Now how was this dumb?

I admit I would PREFER to do the OEM repair with OEM equipment. And if it fails I will.

So far its been funtioning perfectly.

Edit: As clarification, this was the new mount.. NOT the original round 99' mounts. It had been replaced prior and in the past few years with the new style. But because of over compression the mount had failed.

 

Did not change the tranny mount. I'm having symptoms yet.. but when I do I might evaluate doing it myself versus having someone else do it. Its the press fit in. Not sure I feel like using some brake pads with holes drilled in them..

 

If you have a later car with the new mounts you'll probably NOT need to Macguyver the spacer like I did... It really is easy.

 

All answers given respectfully.. .

#1. If the threads are that degraded with removal.. would I want them cleaned and prepared with a tap and die or re-used. That is a question for the owner. It is very much appreciated cost wise to clean and re-use. Or.. just buy new bolts and nuts and re-apply. You know its going to work. Regarding the physical labor of removing 5 bolts per side, replacing, and then reassembling... what would a professional do differently?

#2. Ergo it didn't.

#3. So the old mount is a single cylinder of metal surrounded by rubber with a bolt going through it with a large washer on the bottom and a washer on the bottom. When you torque the bolt throught the center, it compresses the metal cylinder (lets say 2.5 inches long?) between two washers. The new design uses a shorter metal cylinder that abuts the engine mount on the top with no washer, and has a metal masher with a built in spacer on the bottom. the main bolt is torqued to compress the shorter metal cylinder. When you put the washer on the newer style mounts, there is a space between the large washer on the bottom and the metal cylinder in the center of the mount. As you know with the newer mount, this is filled with a thicker metal extension ontop of the large washer on the bottom, that in essence makes up the difference in distance in the mount that was lost from the prior design. The difference in height from the inside cylinder to the flatter aspect on which sites the lower washer. +/- some compressible rubber of 1-2mm lets say. Measured the difference with my calipers.

As I understand it, the frames crack on our early cars with track use even with professionally installed motor mounts, with proper spacers.

How do I know it works as intended? Comparable vibration reductions to 360's I ride in, and reduction in the vibration in my car. I didn't see in the WSM a specification for engine deviation and motion under operation at a given RPM. I also don't see any difference in operation with other 360's I've ridden in or seen running. Is there a spec that I haven't seen?

In addition, on inspection of my cars frame. There is no cracking.

So.. I reiterate with only the highest regard for your input here.. there is no cracking, reduction in vibration comparable to other cars I ride in and observe operating, no further compression in the rubber, no new vibrations, no shifting of the bolts, no bolts coming loose.. if I have the results that appear the repair functions equivalent to OEM, exactly how don't I understand the dynamics? I just don't understand what I'm missing?....