John McM

Speaking of closing the case, this is a minor nightmare as no-one appears to do it the same way e.g. The 'modern' methods start with the through bolts but the workshop manual starts with the case peripheral fasteners. The reason this is important is that there is 45 minutes to put o rings in place and do up 30 plus fasteners and there are two competing priorities.

1. The through bolts control the area around the crankshaft and could impact on bearing clearances.

2. The peripheral fasteners control the case seal integrity.

On balance I prefer the modern method as I'm more concerned about bearing tolerances over the longer term.

John McM

The other nightmare is sealant choice. I will likely stick with the workshop manual spec of Loctite 574 due to its working time of 45 minutes. The Threebond product skins quite quickly in comparison.

Around the nose bearing there are so many choices. I've decided to use a light smear of Loctite 574 on the main area next to the oil channel entry, Dow Molykote 55 on the o ring and a light smear of Curil T on the edge that sits on the case edge. The leaking nose bearing appeared to have been installed completely dry so anything is an improvement.

C4inLA

That #8 bearing is quite the engineering feat. Are all the slots, holes for lubrication flow? It was interesting in the last months of my "little" project to sample all those sealants.. Add Moly 111 and the EP clutch parts grease and they all feel quite different between the thumb and finger. That Curil T has a unique feel. Closing the case, I'd be having dreams about it, happy dreams!

John McM

Oil enters through the side channel under pressure, circulates around the internal bearing surface which touches the crankshaft and flows back into the case. The two holes in the back are to allow oil that tries to escape the bearing area to flow back in the case as does the slotted relief channel by the O-ring.

I'm working out how to film the case closing. Right now, I'm thinking a Go-pro on 2 second frame grabs would equate to a minute on YouTube. Not an original idea but I'd like a record of it for posterity.

John McM

The Case reseal is on a countdown to this time next week.

I'm often impatient so forced time to think and research is helping formulate a hopefully well thought out plan.

The big question throughout the teardown was how to reseal this to end up with a leak free engine, particularly the nose bearing area. Part of the process is understanding how Porsche engineers intended the oil system to work, then I can understand why people propose what they do and whether I'll go with it or not.

To better understand it I researched basic oil system theory. Wow, so much to contemplate. I didn't realise that the system design was so complicated. Basically the pump produced pressure forces oil along galleries where their size and part tolerances determine the flow and pressure drop at individual points e.g. If bearing tolerances are worn the pressure is lower as more oil is lost at the bearing face than intended. That's why a worn engine may show reduced pressure.

The other important point is that oil flows from high to low pressure zones and Porsche have created flow points to pressure drop zones, which keeps the oil going where it should be going. With respect to the nose bearing this is critical.

John McM

What this means is that I no longer think I should interfere with the wider bearing area as this is part of the pressure drop zone i.e. The more pressure drop areas I block off the less the pressure will drop and flow where intended. What I will do is lightly coat the immediate area around the high pressure feed area to minimise the oil entering the bearing exterior but otherwise I will let Porsches design do its work where the o ring and nose bearing seal are the main defence against oil leaving the case if the pressure drop points are overloaded.

John McM

Pics say it all

John McM

Old and new, albeit the new ones were made in 1997 and stocked in 8/98. That's one heck of a carry period. I hope the new ones are Aluminum. I'm over Magnesium parts. USD 82 each.

John McM

Proof of concept with the sealant method. It appears conclusive that the best result comes from spreading a thin layer over the area with a sponge. Putting more or having a thick layer just ends up with sealant where you don't necessarily want it.

Three areas with a slightly different application method in each

John McM

Result in each area on the side of the case which had the sealant on it.

John McM

Side view of the same case side. Clear seepage inside the case with the bead method

John McM

Other case half. Nice coverage with each method but again the bead method leaves too much surplus.

John McM

The conclusion is to use the sponge spread method with care as to how much is on the inside edge. While Loctite 574 shouldn't dry in open air areas I found globs on my engine while dismantling it so I don't think it's license to go mad.

C4inLA

John,

Is the center of pic on post 655 the spong?

As I wish I had a map of how all oil flows through the case, were you able to blow air through various oil routes in case halves after cleaning kind of thing? Your keeping all bearings throughout other than #8?

Fun stuff.

John McM

Sponge method is this photo. It's really more about spreading the sealant the way you want it to go than sponging excess off the area.

Btw this was not Loctite 574. I used a past use by date bottle of Wurth Flange Sealant. I'd be worried if my 574 came out with streaks of colour in it.