Cylinder wall cracking thought...

I have been thinking of the cylinder cracking problem in the 996s. If this is a problem, how is the supercharged crowd doing? After all, there cylinder pressure is substantially higher than our N/As which in theory should lead to more failure. And if this is truly a problem, why would Ruf put his supercharger and name on a product that could potentially fail? In the drag racing world, you would fill up the water passages (too an extent) throughout the block of an engine with block cement to increase the blocks' strength, and also increase cylinder strength. I wondered if this is possible in our engines? I want to run a turbo system (my homemade design) in the future but want to run higher than 6 lbs of boost, I want like 15-20 lbs depending on how I am running the car. But to do this, you have to lower the compression ratio. I was wondering what kind of compression ratio change would there be by using thicker head gaskets? I have faith in the 996 block to withstand high hp/tq, due to its 7 main bearings and I want to take advantage of the 4 valve design. The older turbos had 2 valves and barely make the hp of the 996 so I know there is great potential to boost the 996 engine if I can just get the compression ratio down enough without changing the heads and costing big dollars.

Who said that there was a problem with cylinder cracking? I run a higher effective compression ratio that the TT's in my little old stock 3.4 engine with a static compression ratio of 11.3:1.

1999Porsche911- there was a thread about cylinder wall failures I had read on this forum, I think it was called "engine blown" or something to that extent. The person said he was DE'ing and the motor popped, once torn down, he found that he had blown out the top of a cylinder wall. Many others chimed in with the same experience. Then someone had put a link to a British company that bores out the factory cylinder liner and puts like a 2 X's bigger sleeve in the block. I dont understand what you mean by "higher effective ratio" over a TT. Cylinder pressure in a turbocharged engine (996 TT) I would asume is greater than our 11.3:1 engines. I know that "compression ratio" and "cylinder pressure" dont go hand and hand (although there is to an extent a direct correlation) because of camshafts can bleed cylinder presssure (for supercharged applications so boost can be increased controlling detonation) or increase cylinder pressure (for N/A engines to increase power). My point was, N/A motors have no doubt broken cylinder walls. I just dont know if it was from a weak cylinder wall or coolant leaking into the cylinder hydraulic locking the cylinder. Nothing can withstand hydraulic locking and I hope that this is the real problem because if it is the first (just a weak cylinder wall) , supercharging (turbocharging) the 996 could be a time bomb.

Mine was one that cracked cylinder #1. PM me for pics. It is simply a weak spot in the cylinder wall that could have been easily fixed with a small "bridge" between the weak part of the cylinder wall and the block edge, about 1/" away. It may have impeded coolant though. PM me if you have any questions. If I were going to supercharge a 996, it would be a 2002 or newer.

the problem was more with dropped sleves then randomly cracking cylinder walls. If you blow out a cyl wall chance are its from a hydrolock condition where the cyl was filled with water and it tried to compress it, or you overheated the engine at some point and oit lead to a stress fracture. I would not use block filler on a any porsche engine, coolant passages are designe to prevent hotspoting in the cylinders which is a big deal especialy if your gonan be forcing extra air into the engine. YOu can lower the compression how much depends on how thick of head gaskets, but to run 15+ psi your gonna need to get some forged pistons You will also need to tune it somehow along with lots of other things i just did a whole run down about why not to turbo a na 996 search for boost Do a lot of home work and alot of research before you start your project, unless youve fabbed turbo setups before i wouldnt recomned your first one being a porche.

The actuall problem was not that the sleeve cracked per say. The sleeves were slipping. Due to casting problems (not known to Porsche, Block casting was outsourced) the sleeves were slipping. This means that the sleeve would come loose from the block. Then a piston headed twards bdc would grab the sleeve, take it to bdc, and then back up to tdc. Then whamo! Pull it apart and youve got lots of broken parts/cracked head/sleeve/piston/block it all usually depends on where in the rod ratio scope that the sleeve slipped on that cylinder.

Joe - I hate to hear that happened, I pray it doesnt happen to me. Sometimes I think Porsche should owe up to something this unbelievable and uncalled for. Any engine regardless of miles should not have a sleeve slip and Porsche should pay. 99 & pwr2lbs - I was completely wrong on what caused the cylinder breaking, but the British company said, I believe, that it was just a weak casting. Yes, I forgot that the $80,000 car I own doesnt have forged pistons! This is forcing me that much closer to a 964 T.

The Porsche TTs use a totally different motor design and I doubt they share very few if any parts. I believe they are based on the air cooled design of years past although they are water cooled, and have a dry sump oiling system. They are much more robust and lend themselves to being heavily modified for racing. This is my understanding, please correct me if I'm wrong.

Well, I don't lose any sleep over my 996 "timebomb" that has been boosted with an SC for more than 35,000 miles. No seal leaks or burning oil. But, I also do not run the Mobil Water (0W40). When she blows...she blows.

Yes, I dont lose sleep over it either and I dont want to cause panic but on Joe's thread, there were plenty this has happened to. It was not just a one time thing, but I am glad you have had no problems with your engine! I did not know that your engine was S/C'd. I only run 10W-30 in winter and 15W-50 in the summer Mobil 1 because as I posted before, my oil pressure at idle on 95 degrees or higher days in traffic can get down to 0.8 bar. Once I change to the 15W-50, the pressure willl be around 1.2 bar but that still is like 17-18 PSI! Yikes

they use a 964 block with water cooled (not m96) heads. only parts they share are the pulleys and coils

My 2000 996 has 54k miles on it, and last week the lube oil and coolant fluids had comingled. According to Houston based Pro-Technik [phone removed]) and Porsche dealership Momentum, this is a pretty common problem on early water cooled engines, both 996 and Boxster. According to Pro-Technik, the probelm is combination of magnesium and aluminum in the cylinders, heads and block, where galvanic corrosion between the different metals causes the magnesium to corrode. According to Momentum, there is no way of preventing this, and no way to know before it already has happened. Basically every 996/Boxster before 2002 is a sitting duck, knowing that sooner or later this will happen. The only solution is a complete engine change! As a Porsche enthusiast for more than 30 years, I would believe that the Weissach metalurgists would have known this basic chemistry/physics. But now, when warranties are gone, the costs are thrown in the face of unfortunate Porsche owners. Momentum has suggested $18k to $20k for the job. Where is Porsche's liability in this case, where the cause is an obvious design fault? Anyone out there with some good answers?

Welcome to my world Hey really, most any significant issue on the M96 driveline from engine, bearings, gears, shafts, whole gear boxes, etc, can be remedied........with replacement. On the upside, the $18-20K sounds steep......I don't think a reman. plus core plus labor really should be much more than $12K. Fly....hopefully PCNA will step up and help ya out........good luck to ya.

99/100 TIMES INTER MIX IS A BAD OIL COOLER, IVE NEVER SEEN OR HEAD OF THE PROBLEMS YOUR DESCRIBING. DO SOME RESEARCH BEFORE YOU CASUE PANDEMONEM OVER AN IMPORPER DIAGNOSIS ON A ONE TIME SITUATION EVERY 996 IS NOT A TIME BOMB

Magnesium nor aluminum would hold up to the heat and stress of a cylinder. It has to be steel, cast iron, or chromium lined (like aircraft cylinders) which I do not know what Porsche uses. Every aluminum engine I know of uses a disimilar metal sleeve and I have never heard of a reaction of the two causing issues, I believe there is more to it like, fits and clearances. Although I dont claim to be an expert, just my knowledge of engines over the years.

996/986 cylnder are made of Nikasil

That's just plain wrong. Every Porsche I've owned has had aluminum cylinders.

You are wrong, you have to have some kind of coating (nikasil, chrome) or the alunminum of the piston and the aluminum of the cylinder would gall, not to mention the steel rings on the pistons would tear the aluminum cylinders instantly. Not to mention forged pistons are a harder aluminum than the aluminum of the cylinder. The piston would seize in the bore without a hard coating over the aluminum.

You are correct. You cannot have, for example. aluminum to aluminum contact as it creates too much friction. Nikasil or some other coating is needed to at all contact areas.

How about Aluminum and silica? Alusil. 951 motors. And in your post it appeared to me you were stating that aluminum cylinders wouldn't hold up without a sleeve or chromium plating. Saying that a nikasil coated cylinder isn't aluminum is silly. Kinda like saying your wheels aren't aluminum because they're anodized to protect the finish.

Aluminum cylinders would not hold up. You cannot claim that your cylinders are aluminum when it is sleeved or coated with another material. The cylinder is the inside of the bore and since it is sleeved or coated, the cylinder is not aluminum. The block may be aluminum, but not the cylinders. Is a wooden baseball bat that is corked, a wooden bat or cork?

Mine must have been the 1 out of 100...but seriouly...intermix in early 3.4L is a documented problem...the coolant and oil run very closely together in some parts of the engine, in the block specifically. They are sperate, but the walls break down and they mix in isolated areas....My car did this and the engine was replaced under warranty at 74K miles. I would not call the 996 a time bomb, but there is some merit to the diagnosis....now 18k is WAY too much for the repair.

inermix is a docmented problem. Headgasket failure, oil cooler failure and sleve failure. im yet to take one apart that had broken down passage ways or material from block break down in the the coolant or oil. 18k is too much, engine is about 9k + labor 2-3k

So that round thing that sticks up from the bottom of the block isn't a cylinder?

The pistons do not touch any aluminum, regardless of what you want to call the material that makes up a cylinder. If you want to be percise, the piston touches nothing in a properly setup engine. Aluminum with Silicon, is no longer aluminum. Aluminum to aluminum pistons to cylinder would not last long before the engine seized up.

Okay, I dont want to get into a pissing match, but those pictures do not prove anything. Where the carbon build-up is (very top of cylinder) would show if the cylinder is lined or not. Let me back up, I am a aircraft mechanic and the horizontally opposed motors of aircraft are of very similar design of the air-cooled 911 variants. YES, the cast cylinder is made of ALUMINUM, but the inside lining is of thousandths thick chromium in SOME but not all engines. They first plate the bore of the ALUMINUM cylinder with chromium, then they reverse the polarity and the chromium cracks, leaving a nice crosshatch for oil to cling to. If you had the cylinder completely cleaned to a shine, I believe you would see a parting line, showing where the aluminum ends and the plating of whatever material (nikasil, steel) begins. If that cylinder does not have some type of coating to protect the ALUMINUM, I will not know what to say other than I was wrong, I apologize, and you learn something everyday.

Well, my cylinder #1 intermixed the coolant with the oil - WHEN THE CYLINDER CRACKED IN 2 PLACES. Instead of guessing what the problem was and buying a new motor, I paid a guy to tear the motor apart so I could see EXACTLY what went wrong. At first we figured it was a slipped cylinder lining (as they cannot be aluminum as posted above), but that did not turn out to be the case. Newport 996 - how did you get PCNA to replace the motor at 74K under warranty? Was it CPO'd? Are you the original owner? They told me to pound sand when mine had only 52K miles.

hard to tell what the casue of failure was after the fact, if the head gasket fails it will flood the cyinder and hydro lock usually destroying the piston or the cylinder wall or valves or rings ro all of the above

Hi I have a 2001 c4 cab which has recently suffered from a cracked cylinder 1. Porsche really screwed up with these engines! does anyone know whats the cheapest fix for this? and how much it would cost?

A used engine is the cheapest route and will cost between 6-10k. Tearing the engine down and having the cylinders fixed will cost minimum 6/7k DIY (4k alone for the larger bore), assuming that is the only problem... having a shop do it will be in the 15-20k range. Used engines http://www.flat6innovations.com/shop/home.php?cat=394 Sleeving http://www.lnengineering.com/boxster.html "In either situation, we can upgrade your engine to use our Nickies™ as long as there are no cracks in the case that protrude deeper than the bottom of the water jacket, where in that case, the integrity of the whole crankcase has been compromised! (see below). If the damage on the crankcase side, the damage is not repairable."

You chose to resurrect a five year old thread about turbocharging to ask a question about your damaged cylinder? Interesting choice...

Quotes source post: 8758587

Best solution:

Yes might be best, but the poster did ask for "cheapest". <COUGH> LOL. Actually sorry... this might be the cheapest solution... Currently bidding at $3999.99 for a 3.4L. http://cgi.ebay.com/ebaymotors/260826154414