Has anyone heard of any cases of bore scoring on the 991 engine? Dropping off my car with my indy for the change over valve job, we were talking about the 997 and 991. He said he had a couple cases of bore scoring in 991's in his shop.

 

Yes, I had it in cylinder #4 at about 18K miles. Started as a faint ticking sound, like a dry lifter. Dealer said keep driving it. After a few thousand miles, it got louder and started consuming oil at a rate of >6qts every 10k miles!!

Dealer finally pulled the spark plugs and #4 was black and wet with oil. Borescope showed significant scoring in just that cylinder.

I ended up getting a completely new engine at 23k miles. Completely covered by CPO warranty. Whew!

Dan

 

BTW, mine is a 2013 C4S with PDK. Always driven pretty gently. Tracked once for a total of about 40min.

Dan

 

Does anyone know if this bore scoring stuff has been fixed for good atleast in 991.2 ? (all that alisul/nikasil and what not).

 

When was the ticking sound most apparent?

 

I have not heard anything about the 9A1 engine and bore scoring. Charles Navarro hasn’t seen it either according to Panorama, March issue, page 90! Do you have pictures of the plug or a bore scope to share?

 

Tampa991 - ticking was apparent at idle and gentle initial acceleration. Above about 2300rpm it couldn't be heard.

Dan

 

Alisul/Nikasil hasn't been used in quite some time - 9A1 have cast-iron bore liners, 9A2 is Rotating Single-Wire" (RSW) iron coated lining, which I have read is like 3-D printing on the cylinder head and supposed to be very robust.

sean

 

9A1 uses Alusil bore lining per Flat-6 and many other sources. I had slight bore scoring confirmed on my 997.2 (9A1) that consumed about 1liter every 1500 miles. Just did UOAs to stay on top of wear and aluminum content to make sure it wasn’t getting any worse and kept topping up until I traded in for 991.2. Drove it like that for 5 years.

https://rennlist.com/forums/997-foru...l#post14570999

 

It exist. Not as bad I’d say as M96/97 but I’ve talked to more than one or two that’s tore into 9A1s. Here’s a good read - https://rennlist.com/forums/997-foru...l#post14573451

 

I stand corrected. I thought Porsche had made the change after the M96/97 Series.

 

Here are some photos from when they discovered the scoring in my 2013 991 C4S. I also have to correct myself, it was cylinder #1, not #4. You will see attached a spark plug from #1 (very black) and #2 (clean). There is also a photo from the borescope showing the scoring in #1.

Dan

 

Here is a 9A1 from a 997.2...still havent heard many cases of the 991.1 though..likely because we haven't had enough miles build up in this generation.

https://www.youtube.com/watch?v=02HxKanh-JY&t=324s

 

Must be a rare issue in the 991 platform. I had my spark plugs changed at 33k miles on my 2013 991 3.4 and they were clean as a whistle.

 

Wow, it just amazes me, Honda and Toyota can build pretty much bullet proof motors but we have these crazy odd issues with just about every generation of 911. Okay before pounding, yeah I know these are high performance cars, and I am a 911 fanboy, but still, at this point you would figure they could get past these crazy things like PDK bombs, IMS/RMS, bore scoring. Now with that said, my 911 is going nowhere.