99firehawk

996/986 cylnder are made of Nikasil

Russ Murphy

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

Tippy

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.

1999Porsche911

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.

Russ Murphy

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.

1999Porsche911

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?

newport996

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.

99firehawk

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

Russ Murphy

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

1999Porsche911

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.

Tippy

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.

joes c4 cab

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.

99firehawk

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

msalamza996

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?

logray

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."