DSC800

. . . for killing the joy of finding and enjoying a 996 I say the winner is: Bore Scoring! At least with the IMSB you can be preemptive and take action at a reasonable cost but with BS there doesn't seem to be a definitive cause and there is no fix once you've got it.

Anyway, I'm here in San Diego and this is my first post. I'm looking for the nicest 996 6spd I can get for around $20k. Been reading a lot here and elsewhere and watching the excellent Flat Six series but I still can't get a handle on the volume it affects. I know my best bet is to go with low but consistent miles, known usage and service history and buying an example from a warm climate AND then get a PPI that includes scoping the cylinders and oil filter inspection. But still, what is the best guess as to how rampant this problem is? AND, is it really just inevitable with enough miles? When (or if) I get mine I will have the PPI focus on this problem since any external failures (water pump, AOS, even the transmission) post purchase will seem relatively minor.

From my readings, estimates that the single row IMS failure rate is 5-10%, double row is 1-2% but anyone have guesstimates on what percent of engines will get scored bores by a certain number of miles? Thanks much in advance.

Brian996

This is also not an issue for the model year 1999.

996.2

200,000 miles is good before major engine work. Porsche knows percentage of 996 engines that reach 200k, major engine builders Jack Raby and Barry Hart can probably provide a good estimate. I'm not aware of anyone outside of Raby and Hart that have enough data points to make a reasonably accurate estimate.

Cylinders were a design flaw. Mk2 996s get bore scoring and Mk1s bore scoring and cylinder ovalization leading to cracking. Would be great if experts would provide estimate how many likely to make it to 200k.

85eurocarrera

Hint; when taking tech advice from forum, vet/research it's from respected/reputable members. Click on members screen name and scroll through their comments. Try brian996 for example.....

993GT

I've seen more d-chunk failures than anything

Scott at Team Harco

You again.

Where is there mention of 200,000 miles?

Exactly. Bore cracks left undetected lead to d-chunk. Put that ahead of IMSB. Maybe even ahead of bore scoring. YMMV.

billh1963

say what?

Scott at Team Harco

Forget it, he's rolling...

NuttyProfessor

Cylinder Bore Scoring vs. IMS Bearing Failure? The Battle for Ultimate Champion of the M96 Knockout, huh?

Is this like Rocky Marciano vs. Joe Lewis or Mike Tyson vs. Muhammed Ali?

My thoughts...

Both problems can eventually lead to catastrophic failure. Most owners of the 996 wouldn't dispute that claim. However, one is more predictable and easier to diagnose than the other. One is quicker to death and loves the element of surprise, the other is a slow choke hold that will eventually take out the engine as well. Therefore, both of these problems are not something to take lightly as potential owners of these cars. Most people with a simple bore scope and a pair of mechanic's ears can diagnose the health of the cylinder bores. Not the case with a failing IMS bearing.

But how would one truly know the health of a intermediate shaft bearing?

Many would claim that you could keep a close eye of ferrous metals in the filter and sump, but what if the seller is changing the oil more regularly and cleaning the sump plate. The tech pulls the filter during a PPI and boom, nothing in the filter media. Clean! But still, a sleeping giant is about to awaken. You jump on the forums and drink the kool aid that says, "These IMS bearings are unlikely to fail". This is kind of like when the doctor advises you about high blood pressure because it "runs in your family". You brush it off because, "My great grand daddy lived to be a 105!!!". The doctor insists you change your diet and begin regular exercise, but you ignore it and then one day while driving to work on a calm day... boom! Out of no where comes a heart attack!!! Dead!

Cylinder bore scoring on the other hand, is like having blood work done and CT scans and the doctors conclusively diagnosing the early onset of clogged valves on your heart. You're given a prognosis and a window of time for intervention. It's up to you to make the right choice. Jake Raby says this is a good failure to have, because if you catch it early enough, you can save the engine. Unlike IMS bearing failure, it's not as unpredictable. Most people will begin hearing a ticking sound and then with a simple bore scope evaluation, rule out all of other possibilities.

IMS failure is like surprise attack. Ambush if you will. Bore Scoring is like seeing the enemy far in the distance.

My vote is IMS failure being the worst.

996.2

If buyers knew percentage of 996s whose engines reach 200,000 miles before major work, they could estimate the chances at 133,000 miles they spending $11k-25k and lots of time working on that engine. After Nikasil cylinders installed in engines like yours it would also be good to know how many as % reach 200k.

dporto

Uh... Yes it is - Where did you glean this remarkable wisdom from? The internet perhaps?

Scott at Team Harco

I'd venture to say that an extremely small percentage of these engines reach 200,000 miles before major work is needed.

I'm still not understanding where you came up with that number and how it applies to this thread.

Optionman1

“Seldom right but never in doubt”

wyovino

"I don't own a car and this is my first post, but I know everything." I just don't get it.

5CHN3LL

I'm assuming this (inaccurate) statement is based on extensive searching...