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bazhart
Approved Trader


Joined: 20 May 2009
Posts: 974
Location: Bolton Lancashire


PostPosted: Fri Sep 20, 2019 9:05 am    Post subject: Reply with quote

I’ve taken pictures to help explain but can’t easily upload them – I can email them to someone to upload if there are any volunteers, otherwise similar pictures can be found on our website www.hartech.org

The normal potential problems with the cylinder design are scoring/scuffing & cracking.

Scoring isn’t as common in the 996 3.4 engine as the 3.6, 3.8 & 3.4 987 models but it can still happen, particularly with the Ferroprint pistons.

There are numerous contributory factors with scoring but the underlying issue is that the cylinder bore running face (Lokasil) isn’t quite up to the job in many cases. This is why we choose to go with Nickel Ceramic plating (like in the Metzger engine) as a running surface which is much more durable – it is electro plated onto an aluminium alloy wet liner which shares the same expansion and contraction rates as the rest of the block so is nice and stable in both the deck height and integrity of fit rather than a different material with half the expansion and contraction rate.

Cylinder cracking is a totally different issue and comes about because the original design is essentially a tube of metal just surrounded by water without any support at the top. The thrust loading over the years pushes against one portion of the cylinder and it gradually goes oval and eventually cracks. Our new cylinders are a “top hat” design so naturally stronger and are locked against the casting in a precision machined diameter - so cannot move so will not migrate oval and crack. The original design is an “open deck” whereas the wedging of our liner against the other part of the block makes it more of a “closed deck”. (Incidentally, this isn’t a classic problem with the smaller engines as the cylinder walls are thicker & stronger).

The “closed deck” element of our liner can be re-produced by infilling the space with a support ring of metal.

The pictures you showed me yesterday David are original Lokasil cylinders but with support rings fitted – hence them being described as “closed deck”. They are NOT liners nor Nikasil plated. They don’t look like our work either (well certainly not anything we’ve done for the last 15 years).

Going off tangent a little, there are 2 classic areas in these engines which will eventually lead to a failure through natural wear & tear/degradation – cylinders gradually migrating oval eventually cracking & crank shaft bearings wearing out. There’s a pattern where both seem to start happening at similar mileages (90k-100k upwards). There are obviously lots of cases where engines last longer but there are also others which don’t quite make it (we have 2 in at the moment – 1 at 75k and 1 at 80k).

Cylinder cracking isn’t too much of a drama – a re-build is needed but the damage is isolated but crank shaft bearing failure is another story and a disaster. The crank & rod will usually be wrecked and potentially the carrier. The debris then usually spreads and will kill the oil pumps and, more often than not gets into the cylinders damaging pistons and potentially the bore surface material. In the very worst cases the rod breaks and the whole engine can be smashed and written off. Cranks, carriers etc are getting much harder to source & second hand values are creeping up.

Consequently, there’s a very strong case for replacing the crank bearings as the mileage gets higher before they’ve failed, particularly if the owners plan is to keep the car for some time.

Hope that helps !

Grant
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jond58
Monza


Joined: 19 Jun 2017
Posts: 213
Location: York


PostPosted: Fri Sep 20, 2019 10:07 am    Post subject: Reply with quote

Sorry to add confusion but we’re Porsche not offering the short block at a massively discounted price ? I’m sure I read somewhere a figure of around £4K? Given the ‘100k mile’ concern and my useage as a weekend toy of 5k miles for four grand I’d get 20years of useage?!?
 
  
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eabeukes
Monza


Joined: 30 Jan 2018
Posts: 181
Location: Aylesbury

1999 Porsche 996 Carrera 2

PostPosted: Fri Sep 20, 2019 10:24 am    Post subject: Reply with quote

jond58 wrote:
Sorry to add confusion but we’re Porsche not offering the short block at a massively discounted price ? I’m sure I read somewhere a figure of around £4K? Given the ‘100k mile’ concern and my useage as a weekend toy of 5k miles for four grand I’d get 20years of useage?!?


This was a mis-quote by a magazine, with Porsche UK confirming the prices of short blocks were still way higher (and still with the same inherent faults) than going to Hartech (others are avaialble)
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DAVIDGT996
Trainee


Joined: 24 Feb 2019
Posts: 75
Location: Colchester


PostPosted: Fri Sep 20, 2019 10:47 am    Post subject: Reply with quote

jond58 wrote:
Sorry to add confusion but we’re Porsche not offering the short block at a massively discounted price ? I’m sure I read somewhere a figure of around £4K? Given the ‘100k mile’ concern and my useage as a weekend toy of 5k miles for four grand I’d get 20years of useage?!?
i looked into that as well with Design911 Uk but found as my crank is not serviceable I would have lost the return of the surcharge £4K ish?
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DAVIDGT996
Trainee


Joined: 24 Feb 2019
Posts: 75
Location: Colchester


PostPosted: Fri Sep 20, 2019 11:25 am    Post subject: Reply with quote

bazhart wrote:
I’

The pictures you showed me yesterday David are original Lokasil cylinders but with support rings fitted – hence them being described as “closed deck”. They are NOT liners nor Nikasil plated. They don’t look like our work either (well certainly not anything we’ve done for the last 15 years).

Hope that helps !

Grant
Thanks for this. I am a bit clearer now on what has failed now. which looks to be the original cylinders.
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eabeukes
Monza


Joined: 30 Jan 2018
Posts: 181
Location: Aylesbury

1999 Porsche 996 Carrera 2

PostPosted: Fri Sep 20, 2019 12:20 pm    Post subject: Hartech supplied photos Reply with quote

Photos from Hartech:
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arry wrote:
To hell with resale; drive it hard, enjoy it, enjoy maintaining it.
 



IMG_3949.JPG
 Description:
Support ring fitted to an original cylinder – note the support ring re-produced.
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IMG_3949.JPG



IMG_3968.JPG
 Description:
Hartech “Closed Deck” wet liner fitted ­– note the space around the cylinder “filled in”.
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IMG_3968.JPG



IMG_3951.JPG
 Description:
Hartech “Closed Deck” wet liner – note the “top hat” shape.
 Filesize:  108.83 KB
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IMG_3951.JPG



IMG_3955.JPG
 Description:
Original “Open-Deck” design – note the empty space around the cylinder.
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IMG_3955.JPG


  
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DAVIDGT996
Trainee


Joined: 24 Feb 2019
Posts: 75
Location: Colchester


PostPosted: Sat Sep 21, 2019 8:09 am    Post subject: photos - open deck Reply with quote

On the open deck photo I can understand now where the weak spots are - I assume it's where the gap between the outer cylinder wall and the block is the greatest.

The pressure in the cylinder is greatest at the top so that's where the strengthening work is concentrated with the trade off between using thicker grade metal for strength and the depth at which go down the sides and restricting the coolant flow around the cylinders. I assume that's what is meant by 'wet' and dry closing? Correct me if I am wrong as I am only just learning stuff.

When did this close decking start to happen on the Porche 996/997 engines and what version are we on now? I was looking at deck closing used by a Sabaru racing team who say they are on version 4 having coupied the Japanese original deck closing design in 2001 and then tweaked it. Version 4 is where they use thicker grade metal at the weak spots and thinner grade at the not so susceptible areas whilst maitaining the cooling channels/properties.
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DAVIDGT996
Trainee


Joined: 24 Feb 2019
Posts: 75
Location: Colchester


PostPosted: Sat Sep 21, 2019 8:33 am    Post subject: Retaining rings Reply with quote

Going back to my engine problems - if the engine has been broken before at some stage would you just do that to put in retaining rings on all 6 cylinders? Do you just take out the engine out to perform preventative maintenance.

How can you tell if the bores are still orginal or have been sleeved at some stage?
[/i]
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MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7255
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Sat Sep 21, 2019 8:39 am    Post subject: Reply with quote

I would open an engine to do preventative maintenance by changing the bearings, I wouldn't do it to fit retaining rings. Most people wouldn't do it at all, believing that these engines will go on well past 100k miles without problems. Some will, some won't.

I would imagine the bores would look different, if liners have been fitted then it won't look like part of the original casting.

MC
 
  
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cheshire911
Estoril


Joined: 10 Jun 2012
Posts: 3846



PostPosted: Sat Sep 21, 2019 9:13 am    Post subject: Reply with quote

DAVIDGT996 wrote:
bazhart wrote:
I’

The pictures you showed me yesterday David are original Lokasil cylinders but with support rings fitted – hence them being described as “closed deck”. They are NOT liners nor Nikasil plated. They don’t look like our work either (well certainly not anything we’ve done for the last 15 years).

Hope that helps !

Grant
Thanks for this. I am a bit clearer now on what has failed now. which looks to be the original cylinders.


In all honesty, I'd seriously be guided by Hartech on options moving forward. They have probably the most resesrch and dxperience with rebuilding these engines. You can have the engine removed locally and couriered to Hartech or if you have the cover, have the car recovered to Hartech.
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996 2002 X50 Turbo Manual
"Once bitten; forever smitten"
 
  
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cheshire911
Estoril


Joined: 10 Jun 2012
Posts: 3846



PostPosted: Sat Sep 21, 2019 9:14 am    Post subject: Reply with quote

DAVIDGT996 wrote:
bazhart wrote:
I’

The pictures you showed me yesterday David are original Lokasil cylinders but with support rings fitted – hence them being described as “closed deck”. They are NOT liners nor Nikasil plated. They don’t look like our work either (well certainly not anything we’ve done for the last 15 years).

Hope that helps !

Grant
Thanks for this. I am a bit clearer now on what has failed now. which looks to be the original cylinders.


In all honesty, I'd seriously be guided by Hartech on options moving forward. They have probably the most resesrch and dxperience with rebuilding these engines. You can have the engine removed locally and couriered to Hartech or if you have the cover, have the car recovered to Hartech.
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DAVIDGT996
Trainee


Joined: 24 Feb 2019
Posts: 75
Location: Colchester


PostPosted: Sat Sep 21, 2019 10:13 am    Post subject: Reply with quote

[quote="cheshire911"]
DAVIDGT996 wrote:


In all honesty, I'd seriously be guided by Hartech on options moving forward. They have probably the most resesrch and dxperience with rebuilding these engines. You can have the engine removed locally and couriered to Hartech or if you have the cover, have the car recovered to Hartech.
The engine is already out and broken.One of the options I have been given is to send bank 2 to Hartech for sleeving/decking work.

As above I have already spoken to them for help/guidance. I am just doing my own research for better understanding on the inherent weaknesses of these engines and the solutions to address these currently on the market.

I am an Accountant with a few clients in motorsport industry but not specifically Porsches- they do Autocross & build sports cars for the Japanese marketplace.
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Dammit
Indianapolis


Joined: 23 Sep 2016
Posts: 2372



PostPosted: Sat Sep 21, 2019 11:01 am    Post subject: Reply with quote

Obviously money is always a factor in these things, but should it not be the defining factor on what you choose to do I'd do both banks at the same time.

The key weaknesses of these 3.4 engines are (in no particular order):

- Bores going oval/cracking
- Main bearings being significantly worn by ~100k (see also BMW's V8 and V10 for this problem)
- IMS bearing (although anecdotally these seem to either disintegrate by 40,000 miles or keep going)

And the tappet chest can crack, but that's very rare I think (under normal operating conditions), plus oil starvation (again, on track-hounds).

For the later 3.6 you can add bore-scoring to the above list.

You can tackle all of the first three during your rebuild, which I would hope would then mean many miles of routine oil and filter changes ahead of you.
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911munKy
Montreal


Joined: 26 Nov 2014
Posts: 559



PostPosted: Sat Sep 21, 2019 1:37 pm    Post subject: Reply with quote

^ so not having funds atm for a preemptive engine rebuild due to a house extension (and not wanting to spend £££ unnecessarily) would it be sensible to assume that:

1. Since my 2000 C2 is now on 110k+ with what what I believe to be an original IMSB that statistically it should be OK. (Seals will get flipped off if gearbox is removed)
2. I get an oil analysis every 6000m and monitor the Copper particles of which an increase should indicate main bearing wear, no increase so far and no metal particles in oil filter or magnetic sump plug.
3. It doesn’t use any oil and has always performed well in the 5 years I have used it as my main car all year round and doesn’t have any engine related fault codes relating to cam timing etc according to my OBD2 reader.

My plan is to keep it a long time and when the engine shows it’s first problem requiring removal get all the weaknesses fixed then (unless it hits 200k without any issues first in which case it might get treated to a rebuilds anyway ) thumbsup
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Jamesx19
Nürburgring


Joined: 10 Jul 2015
Posts: 475
Location: Brighton


PostPosted: Sat Sep 21, 2019 7:30 pm    Post subject: Reply with quote

I was following your steps 1,2,3. All going to plan. Oil analysis looking ok for copper content (9 parts per whatever it is, million?) with comment being "no significant wear"

2,500 miles later I'm seeing copper flakes in the oil filter and apparently just caught it before the crank was shagged.

#Just sayin'. It might be I buzzed the engine :dont know: I wasn't worried about working it hard.
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GMG
Nürburgring


Joined: 07 Jan 2018
Posts: 441
Location: Devon


PostPosted: Sun Sep 22, 2019 6:04 am    Post subject: Reply with quote

...these are not Honda engines that will go on forever...they are sensitive and fragile things that have a fondness for melting...it's not true to report that IMS bearings past a particular mileage will be fine...mine collapsed at 69k....crank bearings are likely to be very worn according to reliable sources at 80k plus with the potential collateral crankshaft damage...Oh and they like to score their bores...when mine was stripped 5&6 were showing signs of this;not bad according to Hartech but evident nonetheless...

I say the following ,not prejoratively , but owners are deluding themselves if they believe otherwise hence my repeated advice to potential buyers would be ...buy one that has been treated to a thorough engine rebuild...unless you have £10 k (my rebuild ended up closer to £14k!) available should it be needed ?

They are relatively cheap to buy however they can have running costs aligned with their original £60k price tag...
 
  
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911munKy
Montreal


Joined: 26 Nov 2014
Posts: 559



PostPosted: Sun Sep 22, 2019 8:49 am    Post subject: Reply with quote

Jamesx19 wrote:
I was following your steps 1,2,3. All going to plan. Oil analysis looking ok for copper content (9 parts per whatever it is, million?) with comment being "no significant wear"

2,500 miles later I'm seeing copper flakes in the oil filter and apparently just caught it before the crank was shagged.

#Just sayin'. It might be I buzzed the engine Dont know I wasn't worried about working it hard.


Sounds like it could happen quickly at the mileage I'm at, no idea how much ‘meat’ I still have on my main bearings - “do you feel lucky punk?”

A preemptive rebuild makes sense if you have the funds but I don’t right now. I know it’s going to be about 50-100% more expensive to rebuild if something breaks (or may even write the lump/car off) but if the crank is reusable and the bores aren’t scored (they were good 30k ago when inspected) then I reckon it will cost about £7k to refresh and fix some of the main weaknesses.

I think I should increase the oil inspections to every 3000m from now on for peace of mind.
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Jamesx19
Nürburgring


Joined: 10 Jul 2015
Posts: 475
Location: Brighton


PostPosted: Sun Sep 22, 2019 7:40 pm    Post subject: Reply with quote

Hey 911munKy.

You could always just drop the oil filter and inspect, would be relatively cheap rather than dropping oil that's probably fine.

Might make you too paranoid to drive it like you want though!!

Best of luck with rebuild OP. Lots of choices on offer. The "everything" package might be only be best for a keeper. Otherwise maybe just fixing the broken bits could work for a more reasonable cost.
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g911omr
Spa-Francorchamps


Joined: 29 Sep 2009
Posts: 304



PostPosted: Mon Sep 23, 2019 7:45 am    Post subject: Reply with quote

The fundamental problem with these cars is poor build quality. There is evidence every where you look. The gear shifter for example. Total crap.
Have a gander at the construction of the accelerator pedal...Again, total crap.
I chap I know has a 2000 year BMW 520. The difference in fit and finish compared with my C2 is night and day.
 
  
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bazhart
Approved Trader


Joined: 20 May 2009
Posts: 974
Location: Bolton Lancashire


PostPosted: Mon Sep 23, 2019 9:04 am    Post subject: Comprehensive report on the 4 main failures now available Reply with quote

It must be really hard for owners to know what advice to believe and from whom. Especially new owners who have not been looking at Porsche forums for the past few years (that have contained a lot of information). As a result the same old questions keep re-emerging.

Some contributors provide good honest advice, some purposely mislead (for what they perceive as a personal business benefit), some promote an inferior product claiming no failures (when we see the opposite during rebuilds), and some just have not researched things well enough or from a professional enough background and jump to conclusions from a small number of rebuilds insufficient to draw reliable correlations from.

It is a minefield and so to try and help we have put together a report on the 4 main problems afflicting these engines. For anyone unfamiliar with our history, I would guess we have been involved in the highest number of rebuilds for the longest period and have professionally qualified and experienced engineering staff, a fully operational machine shop that manufactures parts and a superb record of Porsche racing Championships in different classes and events.

TECHNOPHOBE WARNING.

The problem for us is that whereas some of the issues were easy to identify, simple to solve and the results have proven the test of time, others are really very complicated, took a long time for us to understand and will take a lot of time, patience and some engineering knowledge to follow.

We have therefore put together this report into IMS Bearing failures, cylinder cracking, “D” Chunking, Cylinder scoring and Gen 2 cylinder seizing (with a comment on less common problems including crankshaft regrinding at the end).

It includes descriptions of some basics needed to really understand the content, a short simplified version and a long detailed alternative, an index (at the end for those only with time to skip through it) and a bio of the writer (for those unsure who and what to believe).

To obtain a copy you need to contact Sharon at admin@hartech.org from whom you will need to accept a confidentiality agreement before we send on our valuable intellectual property to help you.

We are not sure if this is the best way to help so constructive feed back will be gratefully received via direct E-mail to Sharon. Having spent hours writing it I will not be personally responding to arguments about it on this forum. For readers who found it helpful there may be future additions circulated if requested.

Baz
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