htny

as someone who bought about 6 months ago, I felt that the turbos dropped earlier (only speaking to CPO), but it's not scientific, just studied

chsu74

I am not surprised with Bruce's decision and saddened by his departure.

pongobaz

+1. This is getting out of hand.

phaphaphooey

School is in session. This is the best I have ever seen someone take Ben to task on one of his usual opinionated musings. So, what happened to the nicer kinder Ben from 2 weeks ago?

manny_g

i read a thread on the 997tt board where a guy who just purchased his tt with less than 500 miles has to have his engine replaced because of a porous block. this was the condition as explained to the owner by the tech at the dealer.....porsche wants to replace his engine but he is pushing for a new car, can't blame him.

Riad

I love my engine.

salayc

I agree that the argument is mostly specious, however, these terms have real meaning in the industry, and if people want to make informed decisions about their cars, the first step would be to understand their construction to be able to separate the hype from fact. I think it's far more important to understand the M96 engine block than to continue to post pure conjecture like: "engines fail because they are garage queens", or "no remanufactured engines have ever been replaced."
Perhaps I am alone in this, but I think spending some time to learn about the engines might lead to more informed decision making rather than listening to all of this hype.

Benjamin Choi

if you actually read streather's 996 book and matched it to his lame claims above regarding the 996, you'd laugh in his damn face and ask if he's senile. look past the rather insulting, childish words he spouts off at a guy who's confronting him of his erroneous ways. he's huff and puff because i cut into him and he knows it. i hardly ever traded posts with the guy until this here today.

taken to task? pls. he's gettin worked by me. special contributor? WAHAHAH laughable.

insite

this behavior is quite bizarre; are you off your meds?

Benjamin Choi

yea you took the wrong bottle from my cabinet bro - don't drive call the doctor cuz it ain't propecia

pl

where is bob and dell when we need them THE MOST?

htny

I'm with you man, more technical less BS, but it doesn't matter what we classify Lokasil as, it only matters what Lokasil actually is. Liner/Lining whatever people want to class it as, just doesn't mean anything, it's a different type of process which neither word serves well enough to be helpful to us. I feel like the very fact that we are debating over such fine points illustrates that we don't want to understand the process/construction as novel, and would rather try to equate it to something we are familiar with by throwing it in a box. Instead of worrying about how to classify Lokasil, I feel like it's better just to focus on understanding the process itself, its functional goals, and just how integral it is.

I think clearing up misconceptions begins with sharing information from relatively authoritative, or at least somewhat judicious resources. To that end, here's a nice piece from PCA which I found helpful:
----------------
Scott Slauson wrote this up both online in the Boxster section, as well as for Panorama Magazine. See below. Does this happen a lot with the 1999 996, no it really does not. I think yours is the first such report I have. Let us know if your dealer or PCNA will be helping with the cost of the repair.

If you switch to a later car, you should not have this happen. However some of the other issues are still present, those are covered here in the 996 section. See the Car Buying sub-section for the summaries and how that fits by model year.

If PCNA provides you a rebuilt engine, I would be confident in it regardless of year, and it should come with a 2 year warranty in any case.

Scott's original writeup:

With the introduction of the Boxster Porsche teamed up with Kolbenschmidt to manufacture their newly designed water cooled engine. These engines were to utilize the newly introduced Lokasil liners. The liners themselves offer a higher friction free service area . This is most useful in not only the longevity of the cylinder but in the ever growing higher mileage service interval. The cases experienced several issues starting with their porosity . In 1997 many of these newly released engines would seep oil through the cases themselves. This seepage was due to a problem in the manufacturing process. When the cases are made in a high pressure die casting the air in the die has to escape. Should the alloy enter to fast and not let all the air out you would have trapped air pockets. These pockets produced a porous area in where they were. This area would then allow seepage of the oil. The reason it would generally be oil and not coolant was due to the casting process. The air would be trapped in the bottom to center rear of the castings in which housed the oil.

Another well known problem was the liner failures in late 1998 to early 1999. This would have affected the 1999 model year cars only. These failures were also due to a manufacture process of the crankcases or engine blocks. The cylinder liners are made of an alloy made abrasion resistant by adding silicon. Prior to casting the crankcase, the cylinder liners are fixed in position by an operator , then surrounded by a conventional aluminum alloy casting. This is done by inserting the preformed cylinder liners manufactured by Plochigen-based Ceram TecAg in a special freeze casting process into the die. The dies are then closed and a high pressure die casting (HPDC) and squeeze casting (SC) are utilized to achieve this. Three casting machines with a closing force of 1,800 tons are used for this purpose. The advantage of the Lokasil process is that the silicon required is applied only where it is needed. Lokasil base material cost less than Alusil and is easier to process. These liners or preforms are of high silicon content of 20-27% and offer a high reduction to friction. Kolbenschmidt holds the patent to Lokasil and is also known for their Alusil and Galnikal piston liners. Lokasil is a "sacrificial" bore liner comprised of silicon fibers in a binding that, when inserted into the block mold, burns out the fibers, leaving the high-content silicon surface directly in the bores. This actually allows the “sacrificial” liner to become one with the block thus eliminating a separate part in the block.

In 1998 Kolbenschmidt had dropped the casting machine while it was being moved. Do to the time to repair the machine Porsche was in a bind. This could slow the Boxster production down severely unless a fix was found. Kolbenschmidt had suggested using the failed quality controlled (QC) blocks they had. Most of these blocks had casting defect or a porosity problem in at least one cylinder. The fix was simple and by all means acceptable to standards when done correctly. What they suggested was to re-sleeve the bad cylinders. Porsche accepted and Kolbenschmidt began the process of the repairs until the casting machine issue was fixed. This process would start by boring out the failed cylinder to allow for the insertion of the liner. There is also a groove cut around the top of the cylinder to keep the sleeve from dropping. This groove is approximately 2.0mm larger in the size of the cylinders width and goes down approximately 4.5mm. Now the next step was the insertion of these liners. It was decided to press the liners in the blocks. This is where the error occurred. Some of these liners were pressed in at a higher rate than the top retaining ring could handle. This would then fracture the ring at the top of the liner. When this ring failed under operating conditions it would be catastrophic. The ring itself would fall apart inside the combustion chamber. At this time the piston would force this debris up into the cylinder head. The piston rings would grab the liner and pull it down from the momentum of the crankshaft. Some of these engines would be replaced from coolant loss before they totally self destructed in this fashion. This was do to the ring starting to come apart but not fully. This would compromise the sealing of the head gasket and cause the coolant to either be burnt or expelled from the combustion pressure.

Porsche has not divulged exactly how many engines this actually occurred in other than a broad range of 2.5 engines in late 1998 -early 1999 . Nor have they released any engine numbers that have had sleeves installed. Generally speaking the problem would occur within the first several thousand miles. They have been very good in correcting this for their customers in and out of warranty.

Scott Slauson - PCA WebSite - 6/14/2004

Joel Reiser - PCA WebSite - 8/11/2006

jury_ca

Actually, the way to calculate the potential financial outlay (ignoring TVM) is to take the expense (12K) multiplied by the probability of failure.

In the end, it works out to peanuts, so enjoy your cars.

..that goes for you too, space-cadet.

insite

that does a good job of explaining what happened with the sleeved blocks. i think porsche may use sleeve and liner to mean two different things. most of the time when i think of a sleeve OR a liner, i think of a thin cylinder of metal that is NOT aluminum that is inserted into a case so that it won't bind with the pistons (aluminum pistons in an aluminum cylinder will bind without a wear surface).

this is EXACTLY the case with the sleeved porous blocks. they took porous blocks from the scrap heap and sleeved them w/ what was probably steel. the idea was that the steel sleeves would render the porosity problem moot. the further problem with these motors was that in some cases, the sleeve slipped inside the block and caused catastrophic failure.

the standard block, however, has no sleeves / liners in a conventional sense. it's closer to a coating, but it really isn't a coating, either. you can think of metal as a matrix of molecules that look like a 3D lattice. in between these molecules, they put silicon. the combination matrix of the aluminum alloy & silicon impregnation allows the aluminum pistons to slide without binding in the cylinder, as it would were the cylinder strictly aluminum alloy. the hybrid material also has better wear charicteristics than the aluminum alloy alone.

it's a very interesting solution. i wonder if it's actually any cheaper or better than a conventional sleeve would be? afterall, the thermal expansion coefficient of alumnum is huge compared w/ ferrous alloys.....

EDIT: to be clear, the sleeved porous blocks were M96.20 boxster motors; none of these went to the 996.

salayc

Thanks for the article and providing an intelligent perspective. I still think sorting out the semantics is important. For example, if we can determine that early sleeved blocks are prone to failure and the newer KS ATAG process does not use them on the 3.6 and 3.4 rebuilds then that information should help anyone with a blown engine to make a decision or at least to rest easy. (I am not saying the latter is true, it's just conjecture)
To have more members who do their research, and less who post emotional opinions can be very valuable.