Yet another serious M96 problem is porous engine case! The engines can weep coolant or oil into the outside of the engine, or internally, where either fluid is not supposed to go. Fortunately, this is mostly a problem with early production M96 engines, although any year engine can exhibit the problem. Dr. Porsche is probably spinning in his grave and is preparing to haunt the engineers that designed this crap pile.
The only solution is to replace the engine case! Then, you better take your brand new engine case and get it re-sleeved by LN Engineering! Some shops claim to have success in welding up some of the cases where you can access the porous area, but we would not risk doing something like that.
Yet another issue that is serious but not as dramatic is a leaking rear main seal. Sometimes, the leak can be so bad that the engine can loose most of the oil in a track session or in between oil changes. Often, the clutch is ruined by being sprayed with oil. Many times the leak resists attempts to fix it.
The reason why the leak is hard to fix is possibly two-fold; the seal carrier is not positively located by two dowels on the end of the block, only one, so the seal may be installed off-center. The other more insidious reason is the idiotic method of retaining the crank within the engine cases that can allow a lot of tolerance stack regarding the cranks location within the engine!
Later cars have an improved rear main seal and often retrofitting this seal can fix the leak. Sometimes not… You would think an expensive sports car would be a little more figured out before it was released to the public!
The M96-M97 has the crank captured by a girdle that is an independent part separate from the case. It fits tightly within the case. Because of this, the girdle cannot be aligned bored to correct any crookedness it might have. The crank’s location depends on the accuracy of the machining of insides and outsides of the girdle, the case and the clearances and location of the crank within the girdle!
That is a lot of tolerance stack that is difficult for any machining operation to control and impossible for the engine builder to correct if anything is out of kilter. Thinking about the issues that could happen here can make the head spin. Feel like killing an engineer yet? Oil leaks, lubrication, bearing issues and crank failures anyone?
The stupid does not end there. The process of installing the wrist pins is perhaps one of the craziest bits of mechanical dexterity required in the automotive world. See the holes in the cylinder bores? You have to install the wrist pins through these!
Working on this is right down there with installing Nissan Z32 turbos in the car. Let us take that back, it is worse. Maybe complicated brain surgery is easier or vascular micro-grafting.
Ok, the whole procedure is a little beyond the scope of this article, but it involves threading wrist pins through the lined up holes in the cylinders with this special Delrin tool and several other diabolical tools.