Strange oil leak...

So I go jack up the back of my car so that I can swap mufflers....I lifted the back end pretty high so that I can have good amount of room to take the mufflers out. All of a sudden I see oil dripping down from this area, a total of a few table spoons: This bolt is directly below this silver cap thingy: Here's a close up: What is that? So I lowered the car back down....no more oil drips. Started the car...no drips. Needless to say I didn't proceed with the muffler swap. Too frustrated... Hoping this leak isn't something major. FWIW my car does not leak anything normally. Anyone have an idea?

That is your hydraulic motor mount. Did you use any part of the engine as a lifting point to jack the car up?

I jacked it like this (borrowed pic from renntech.org): Does this mean I need to replace it? Is it hard to do?

You can not lift the car by the engine, the motor mounts are over-engineered but not by that much. They are the exact same hydraulic mounts that are used on the 993 that fail in the exact same way. I'm sorry you had to discover this on your own, I tried to warn people HERE . Fortunately the MSRP on the mounts is only $137USD. When it comes to safety issues ignore any time-saving suggestions that can't be backed up in writing. Especially if the factory specifically warns not to do something and a CTG trainer says otherwise... At the very least a warning should be included mentioning the potential problems. So that if you have no alternatives you're not flying blind. Next time jack the car by using the following lifting points. Yes you will need to replace the busted mount and you should remove the other and check it before ordering a new one just to make sure the other is ok. The procedure is real simple. Put your jack under the engine, engage the jack just enough to take pressure off the mounts (you'll see the engine move slightly). Then you can undo the lower bolt and the two upper bolts. If you compare your now busted mount to the hopefully still working mount, the busted mount will have some rubber hanging down further on the bottom side. When you install the new one(s) make sure to use a torque wrench on the fasteners. If you don't have one it will still be way cheaper to go and buy one rather than having your dealer replace the mounts.

What do you think happened that caused the mount to start leaking?

Thanks! What torque spec should they be tightened too?

I've never taken a damaged mount apart so I can't say with 100% certainty but I do know that it was a result of using the engine as a jacking point. I would also be concerned with the bearing cage and the crankcase, the 996 already has enough problems with these moving on their own. Engine carrier to Engine Mount (M12) 85Nm (63 ft-lb) Engine Mount to body (M8) 23 Nm (17 ft-lb)

I have to disagree with your assessment of lifting the car from the crankcase being the cause of this engine carrier mount failure. While it is a possible cause, it is most unlikely. The mounts can easily support the weight of the chassis and running gear from a slow lift. And while the car should not be supported from the engine for prolonged periods of time, the time that it would be needed to support it so that Jack Stands can be placed on the rear chassis mounts is well within the compression design capabilities of the mount. If this method of lifting the car would damage an engine mount, then it would be called out as a warning in the Porsche factory repair manuals, and would not be taught as a method of lifting the car at the Porsche technical training centers. What is more likely the cause of failure of the mount fluid chamber was an extreme over-pressure spike caused by the car driving over some adverse road condition like a pothole etc. If the one of the wheels hit something that caused the suspension to hit its bumpstop, but yet had more energy in the impact, that energy would be carried up the suspension carrier into the engine, and through the motor assembly/chassis mount. A pothole impact can send 100Gs through the chassis, motor and up into the body. If the engine carrier mount was not properly torqued to the motor subfame and body, it could compress excessively and rupture. Remember that in normal operation the drive-train assembly is hanging from this mount. I would suggest that the owner of this car also check for bent or out of round rear rims. The suggestion that lifting a 996 by the engine to put jackstands on the rear lifting mounts will cause the rear engine carriers to rupture is nonsense.

These also take the complete torque load.

I don't know the exact specifications for the mounts but I will try to find out. There is a big difference between doing and teaching. What is written in the 996 owners manual? Here are the warnings from the workshop manuals for the 964, 993 & 996 (they all use the same mount): There was no complaint of excess vibration or noise which is one of the symptoms of an improperly fastened mount. The two engine mounts AND the transmission mount see ~650 pounds during normal use (engine ~400 & ~200 transmission). Lifting the car by the engine is placing an additional load (~2000 pounds) on them, possibly 4-5 times what they normally see. Whether you believe it or not this is not a new phenomena, THESE hydraulic motors have been failing this way since 1989. If you lift the vehicle by the engine and the mounts start leaking with the engine still on a jack what does that tell you?

Well, I just love pissing contests with the anointed experts. But I also stand by my statements. True, the mounts for a 996/997 do have their genesis with the 993 (they even have 993 part numbers, 993.375.049.06). Generally if a generic part has a high enough reliability on one model line and has a use in another model, it is carried over. Such is the case with these motor mounts. They have proven themselves reliable over time and thus are still in use. If they were as problematic as is claimed, it is doubtful they would still be in use today. In response to lifting warnings, here in the US there are not the same warnings in the technical manuals about lifting the vehicle as there are in other countries especially in the 996 manuals. The references about lifting generally apply to platform lifts and not jack lifts, and are intended for platform lifting operations where the lift will also support the vehicle for an extended period of time, and to insure that the chassis is not lifted from the floor pan or other non-reenforced areas. Also true that the mounts normally see 600-800 pounds of "pull" on them at rest from the engine hanging. But I must clarify what forces are in effect with lift from the engine. By pushing up on the engine, the mounts would see about 2400 pounds of "push" on them from the chassis compressing the mount. This push also goes from 0 to 2400 pounds. over many seconds. This is well within the design limits of the mount. In a pothole impact situation, the mount may see 24,000 pounds or more of push on it that goes from 0 to 24,000 lbs. in just a few milliseconds, and then 6000-8000 lbs. or more of rebound pull from the engine in a few more miliseconds. These extreme shocks can set the mount up to fail at a later time. The way these types of mounts fail is from a shear tear where the rubber part of the mount is bonded into the metal support ring. The act of lifting the car up by the engine may be the trigger stimulus to cause a damaged mount to rupture, but it was not the cause. If the mount has sustained shear damage from a over-pressure impact, it is doomed to fail regardless. If the mount has not been damaged, no amount of lifting the car by the engine will cause it to fail. Liquid filled engine supports have been around for quite a while and are used on many marques. They are generally reliable but they fail just as often (or as infrequently) on an Audi or a Ford as they do on a Porsche. Invariably the cause for failure was an shock event that the car experienced days or even years earlier. I must also advise that if one does have a ruptured mount, their replacement is extremely easy. Simply support the engine from the bottom with a hydraulic jack, remove one nut that holds the bottom of the mount to the rear engine carrier support, and then on top in the engine bay, remove the bolts that hold the mount to the chassis, lift out the damaged mount and drop in a new one. The only extra steps may be to remove the air cleaner box, or on US cars the secondary air injection pump. Total time to R&R one is under 45 minutes. It is a very easy DIY job. I hope that I have been able to clarify the phenomena that some have been experiencing all these years.

So here's another question. If I use the rear jack points to jack where do I put my jack stands??