Jump to content
Impact Bumpers
MarkJ

Bore scoring?

Recommended Posts

I really like 997's so bit of  a shame they are tarnished with the IMS and Bore score issues but I would love to know just how few out of the thousands produced, actually genuinely suffer from these issues. It obviously was a genuine concern as Porsche altered the engine architecture (from what I've read) to resolve these problems with the gen2. There are other improvements with the Gen2's like DFI and better aesthetics so I prefer them anyway but a bargain 997 gen1 would be attractive.

Share this post


Link to post
Share on other sites
15 minutes ago, MarkJ said:

I really like 997's so bit of  a shame they are tarnished with the IMS and Bore score issues but I would love to know just how few out of the thousands produced, actually genuinely suffer from these issues. It obviously was a genuine concern as Porsche altered the engine architecture (from what I've read) to resolve these problems with the gen2. There are other improvements with the Gen2's like DFI and better aesthetics so I prefer them anyway but a bargain 997 gen1 would be attractive.

I read somewhere it was 5% affected with IMS/rms. The earlier the gen 1, the higher the risk. Think there was an updated bearing in 2006. Bore scoring, that sounds like a use and oil issue. Ragging the motor from cold. 

Share this post


Link to post
Share on other sites

If you want to understand it, read the Hartech stuff - its many thousands of words and forensically detailed, if a little repetitive.

At the risk of over summarising, it is a real design problem (cooling system design, thin cylinder walls, long service intervals) and given the right circumstances all Gen 1 engines are susceptible.  However, not all will suffer as not all are put into that set of circumstances.  There is good news, because you can mitigate the risk - low temp thermostat, best fully synthetic oil changed yearly, don't rag them from standstill.  Its all in the Hartech bible.

If you buy one and its borescoped as "good" and you take the protective measures, then I think you would be very unlucky to suffer, so you pay the market price - which is an uninformed market price which is arguably too high for the risk the average uninformed owner is taking.  However, as an informed owner who can adjust their behaviours accordingly and mitigate the risk, then you are gaming the market a bit.  That and the fact the 3.2s have much less risk to start with - because thicker cylinder walls - was what got me comfortable with the 987S.  If you can buy one under mkt price or damaged and price factoring in repairs, then even better.  Buying as an ownership prospect is rational and justifiable, buying on the economics is harder.

Share this post


Link to post
Share on other sites

From me bruv who has been through this.....

 

"Firstly they’re two different engines. Gen 1 is the M96 (same as the gen 2 996) and M97 (the 3.8S) and on the Gen 2 997 they moved to the 9A1 (as also used in the gen 1 991’s).

Two elements - scoring and ovaling.

The cooling runs from the top down on the 1.2.3 (left bank when you stand at back of car) to bottom up on 4.5.6 (right bank). The causes the right bank to run hotter and makes it more prone to scoring and ovaling. The reason that the 3.8S is slightly more prone, but not immune, is the cylinder walls are thinner than the 3.6.

Combined with the above locasil can wear and break away from the surface making the scoring get progressively worse. The piston start to ‘tip’ which causes the edge to ‘tap’ the heads which is why you listen for the tapping noise.... as well as look for the left sooty exhaust. It’s the left exhaust tip that goes sooty because the exhaust crosses over - I.e the left tip is on the end of the right bank manifold.

If you ignore IMS bearing fear mongering the later 2000/2001 gen 1 996 3.4’s and the 986 3.2S have the most resilient M96 engines.

Incidentally there has been talk of the piston coating being an issue on 9A1 but I’ve not bothered to read in to it.

Basically, you either buy one and accept you may get a 11k bill or buy one that’s already had a rebuild. its still cheaper than buying a new car with high depreciation. Just ducking drive it and enjoy it FFS."

 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...