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Q and A

M96/97 engines

A discussion of the much publicised issues with the Carrera engines in the March 2015 GTPorsche magazine feature by Peter Morgan

A round-up of general questions

The following subject questions are asked and answered below.
Last updated 15 June 2016 (early stage bore scoring spotting):


Q: Have you any idea whether 944 (excellent condition cars), particularly S2 Cabriolets will hold some value in next say 2-3 years please?

A: The 944 market is very interesting at present as the very good condition cars are beating the market. We have seen the very best S2 and Turbos selling for typically £10K when the 'normal' price is closer to £5K. There is every indication that the very best cars are resilient to the effects of the recession and over time won't depreciate with the same rate as just 'good' condition cars. The market for well maintained Porsches has seen something of a mini boom in the past year, and with interest rates in the UK being held low, classic cars are seen as an alternative place to put cash. But this does require care and experience to realise any benefit.
A top condition S2 would fall into that category (as would the 944 Turbo, 968 and particularly 968CS). The coupes are in stronger demand than the Cabriolets and I think the latter require significant care in purchase. They do not hold their value as well as the coupe, possibly because the Boxster is such an attractive alternative. That said, every car should be assessed on its own merits and good cars will always outperform the norm. I always work on the basis that if a car appeals to me, then it will appeal to somebody else later. Top service history (with regular oil changes) is critical for the aluminium block engine's reliability. Things like owner numbers are not so important as the proven condition.    Back


Q: Does the 968 have the same timing belt and cambelt arrangement as the 928.Is the belt change timing critical. If so what criteria apply re frequency/Mileage. Or are the camshafts chain driven. And the timing belt?? I know all this a big job with the 928. Is the 968 similar in that respect.

A: The 968 has a toothed rubber cam belt that should be changed approx every 36-48K miles/4yrs (depending on who you talk to!). It is derived from the 944S2 arrangement with an automatic tensioner, which itself was derived from the 928S4 arrangement. I can't remember which camshaft is driven by the belt (probably the exhaust), but a small duplex chain in the centre of the cam then drives the other camshaft. This is tensioned automatically and the Variocam arrangement also works on this chain (to adjust the inlet cam timing). The sprockets on the cams can wear and this is an area to look out for on an older 968. The whole arrangement is more sophisticated than the 928 because of the variable valve timing.   Back


Q: I am wondering if you can advise me on which are the right tyres for the rear of my car, my car is 1996 993 Carrera (narrow body) fitted with 18-inch turbo (993) alloys at present the tyres are 265/35ZR18 however i have been told i have the wrong tyres and that i should have 285/30ZR18. Which is correct?

A: I think the standard tyre sizes for a Varioram 993 with the option 18-inch wheels are 265/35ZR18, but the Carrera S, 4S and Turbo has 285/30s on 10J rims. That suggests that you could run 285s on the rears but on the narrow body clearance could be an issue at full bump. I don't think 993s ran 9J x 18 rims, so if yours are the standard offset (40mm I think) 10J then its body clearance that is the deciding factor. I think the Turbo and RS run 65mm offset to keep the big tyre inside the arch. I have seen 285s on narrow body Carreras, but I don't know if there are any side effects.    Back

LHD cars

Q: I have read your 993 buyers guide as I will perhaps next year buy a 993 Turbo. I will be looking for a good example in Sweden, Germany or possibly an LHD car in the UK.
Obviously there are some pitfalls to avoid and I am sure I will need some help if we find a couple of good examples.How can you eventually help us? Are other countries worth considering?

A: My experience over the past year (2009) is that most of the good left hand drive cars have already left Britain for Europe, when the UK pound fell against the Euro initially. You might like to keep a watch on the Italian market, as this always used to be a good source for UK buyers looking for a well-priced LHD car. I'm not sure if that situation has changed in the past year.    Back

Rear Main Seal oil leaks on 996/997/Boxster

Q: I have a question relating to a 996. I am now selling the car and a buyer has noticed a minor seepage from the RMS.
There is evidence of an oily area in the appropriate place on the underside of the engine, but no drippage. The clutch was replaced in December 2006 and RMS done at that time. Is there any need to replace in these circumstances?

A: A very high % of 996s that I see have some sort of oil leakage past the rear main seal (or the intermediate shaft seal that is near it). Consequently the general advice is still that it is not worth tearing the engine and gearbox apart unless the oil is actually leaving drips on the ground. Otherwise it can be left until the next clutch change (assuming it is a manual gearbox). It is obviously necessary to check the engine oil at the prescribed intervals, but as long as the oil level is correct, no damage can come to the engine specifically from a leaking rear main seal. Since the Boxster launch back in 1996, it is believed there have been some 12 revisions of the RMS design, with engines built from the 2007 model year believed to be largely trouble free.  Back

Which 996?

Q: I have started window shopping looking at cars priced between £12-25K, this puts me right in the middle of 996 price range. Because of my need for reliability and manageable running costs (I anticipate doing 15,000 miles per year with the car) I have been looking at 3.6 Carrera 2 and 4S variants - the 4S because I like the look more than anything else!Which of the models would you favour - I prefer a manual to tiptronic, if this helps. What annual servicing costs should I budget for.

A: The 996 4S is probably the most popular 996 model and is ideal for high mileage driving. The C2 is a little more focused, but is still an excellent cruiser and prices are very attractive with the car coming off its initial steep depreciation curve. Either model is fairly easy to sell at the right price. Both have very good reputations for reliability. It would come down to service history and condition if I were choosing, with preference going to the 4S if they were the same. The Tiptronic automatic is an excellent choice for any 996 and the unit has proven to be reliable. While those seeking a more focused drive would choose a manual, the Tip has proven to be very popular as an everyday driver. The servicing costs are not really going to be any more than another premium saloon. The 996 has annual services that would cost around £400 with a major service every alternate year (possibly £600). Otherwise it is wear and tear items (tyres, discs/pads, plus aircon condensers perhaps every 4-5 years). There will be other odd items.

As a final note I would choose a 2002 or 2003 model year car rather than a 2004MY. This is because the '04 cars went on to a 2 year/20K mile service interval and evidence is suggesting the complex engines were just not suited to this, particularly when the cars were used solely in an urban/short journey environment.    Back

What books to buy

Q: My husband has owned a 1970 911T Euro spec for many years and is starting to get excited about possibly restoring it. I want to buy some books that will give details about Euro spec cars. Can you recommend anything? We have your book Porsche 911: Purchase & Restoration already.

A: There are not many good references on the practical side of restoration of the early Porsches. As you note, my book with Lindsay Porter (now 25 years old!) is about the only one that gets hands dirty. Without sounding as though I am trumpeting my own books, you might like to consider "Original Porsche 911", (ISBN 9781901432169), which goes into the specifications of the early models. Another good one on the early cars is by an American author Dr. B. Johnson "The 911 & 912 Porsche, A restorers guide to authenticity" (ISBN 9780929758008) (if this is still available). If you want a broad buyers guide, I am afraid it is me again with "Porsche 911, the Classic models (1964-1989)" (ISBN9780954999094).    Back

Buying a 996 Turbo

Q: I have a 1987 3.2 Carrera and am thinking of buying a 2001 996 turbo. I understand 996s can develop a problem with cylinder block ovalisation and cracking, did this extend to the turbo? Is it a model you would recommend avoiding? I would really prefer a 993 but they are so expensive!

A: The 996 Turbo has a completely different engine to the Carrera. It is based on the engine that won Le Mans in 1998 and uses the very well developed crankcase of the 993/964 models. The engine is often called the 'Mezger' engine after Porsche's brilliant mechanical design engineer Hans Mezger, who designed and developed the air-cooled flat-6. Demand for the 996 Turbo is very strong at present as it is showing such good value. The good ones are very good, but care is required. 993 Turbos have become a special contemporary classic, because they represent the last of the turbocharged air-cooled flat-6s.
996 Turbos are still good value, but don't be tempted to buy too cheaply. These cars show a fairly constant list of wear and tear items (aircon condensers, coolant rads, brakes, wastegate controllers, etc) and these can really push up cost of ownership if previous owners have not maintained the car properly. It's important to note that the Mezger engine Turbo was superceded by a brand new 'Gen 2' DFI Turbo for the start of the 2010 model year (August 2009). Back

Buying a 997 C4S

Q: I am in the market of buying a used 2006 06 reg 911 997 4S from a general dealer and require advice on when is the best, usual, time to have an independent inspection carried out by the likes of yourselves.
At the moment, I have expressed an interest in the car and, via email, have only checked that the VIN page details, year manufacture and options list etc meet and satisfy my requirements. I have not seen the car or asked about its general condition other than the dealer saying the bodywork & wheels are in excellent condition. I have yet to talk about a price with the dealer but have mentioned that, as they are not an OPC I will be arranging for an independent inspection. When is the most appropriate time within the dealings to call in your expertise? Before I have agreed a purchase price, after, deposit subject to a satisfactory report etc? Your advice will be greatly appreciated.
My other concern is the time lapse between asking for an inspection and you scheduling it in and in the meantime the unsecured car has been sold to A.N Other. Obviously I understand if the deal is not finalised I bear your costs but I need to understand how your process works so as I do not pay an inspection fee on every car I look at but fail to secure.

A: The way we work is that we are usually called in after a client has first seen a car or has satisfied themselves that the car is what he/she wants. We inspect cars for a good number of overseas or remote buyers, so what we do is to take a lot of photographs to shows the detail condition and any issues. The 230-point check would include putting a laptop on the ECU to check for fault codes, over-revs and record the engine operating hours (which allows us to take a view on the mileage being displayed on the main gauges). We would also give you a valuation on the car, using the same database as the dealer uses. We also carry full trade motor insurance to allow us to drive the car. We always try to complete the inspections within three working days.
If the car is in Hampshire, then it would probably be me that does the inspection. I would call you after the inspection and give you the 'bullet' points of any issues about the car. The main report with all the photos would follow by PDF within 12 hours (hopefully).
There is no standard way of purchasing a car, particularly when you haven't seen it. If you are satisfied that this could be the one you are looking for, then a dealer will, at some point, suggest a deposit. The market is very active at present and an unsecured car may sell. You could try and get a verbal 'first refusal' on the car from the dealer, but most will say 'first come, first served'. If the car sells after you have made the inspection booking, there would be no charge from us if we have not left our office on the day to do the inspection.A deposit of between £250-500 would show him you are serious and it would force him to take the car off the market. I would not suggest any higher sum as other factors as well as the inspection could enter the equation between deposit and completion.
The deposit should be returnable if the inspection shows up any serious issues, but there should be an undertaking that any provisional price negotiated is renegotiable if there are items to be fixed at your expense. If the dealer offers to fix them to your satisfaction, then obviously the price is likely to stay the same. He is unlikely to renegotiate on basic wear and tear items I would find, like worn upholstery, accidental minor scuffs, stone chips and so on. I would expect anything that compromises the roadworthiness and if a service is overdue, to be up for negotiation. If the dealer isn't an OPC or a wel-known Porsche independent specialist, some care should be taken about who does any servicing, repairs etc that may be required.  Back

Choosing the right Porsche

Q1: I am now at an age when I can award myself the car that has inspired me from an early age. Can you advise how I should go about selecting the right Porsche for my budget?

A1: I would first suggest you get hold of a copy of one or other of the Porsche magazines and go and see some of the cars that are being offered by the independent Porsche dealers near you. I would also suggest browsing some of the internet classified ad websites . Probably the widest selection of Porsches can be found at or That should allow you to focus in on a car to match your budget and go and 'kick some tyres' to see what you get for the money. You will find there are some big differences! Once you have got past that introductory level, you will begin to understand the differences in terms of value for money. Look for good service history as the first condition and be wary of any aftermarket modifications. Colour and mileage also affect the value significantly.

Q2: I live in the United States, and am considering buying a used 911. The 911 has always been a dream of mine to own, but a lot of what I read on the internet is beginning to scare me off a little bit, esp when I read of IMS issues on non turbo engines, manual transmission issues on the 996, cylinder scoring, etc...
Which one of the following would you recommend to buy, in terms of the most reliable? 996 Turbo, 997.1 Turbo, 996 C4S, or a 2009 997 C4S?
My original preference is the turbo since the turbo engine is more robust and does not have IMS issues and has excellent power, but the turbo seems to have more wear and tear on the coolant system and transmission than its non turbo counterparts.
Then I have been wondering if I should consider a non turbo but only if the IMS bearing has been upgraded. I have found some used 996s advertising upgraded IMS bearings from LN Engineering.
Finally I started looking at the 2009 997 C4S because of the new engine not having IMS design, but the 997 C4S is still too expensive for me.
What is your opinion, of the cars I listed above, which one would you choose that offers the combination of being the most RELIABLE and most FUN?

A2: There are many variables to consider with choosing a Porsche and I would suggest that you should think about what you want the car for first. A Carrera is a brilliant everyday driver, easy to use and great for driving to work and weekend easy touring. The Turbo is a more aggressive sports car, but still easy to drive. However, it is probably more expensive to run in terms of fuel consumption and maintenance.
If you have concerns about IMS bearing and cylinder bore wear, avoid the Gen 1 997, although the 3.6 models appear less affected by bore wear. The styling of the 996 and 997 appeal to different tastes also, so that helps choose between these. Generally the 997s are better built than the 996 and the Gen 2 997 designed out the engine issues that affected the earlier cars. So far we don't see any trending issues with the G2 DFI engine.
The engine in the Turbos and GTs is one that can trace its heritage back to the first 911 and as such it has a very good reliability record. The G2 Turbo replaced that engine and so these later models do not have so much heritage/classic appeal as the cars with the so-called Mezger motor (named after the design engineer of the engine). For the long term, any 911 with this Mezger motor appears a good buy.
All 911s are fun, but I guess if I had to choose, a Gen 1 997 Turbo would have the best combination of classic appeal, minimal depreciation and good looks. But it does have the ability to wake you up very abruptly on a rainy Monday morning commute to work!  Back

Over-rev events on a 997S

Q: We recorded a series of over-rev events on a 997 S recently (see the data below) using a diagnostic computer to read the ECU. The car was covered by a Porsche warranty and the potential buyer asked if the over-revs were serious.

A: I believe the notes below are drawn directly from the official Porsche guidelines to their dealers on the implications of engine over-rev events.

Engine operating hours counter at the inspection = 1687 hours

The ignition ranges I recorded are as follows:

  • IR1 8799 events with the last at 1680 hours
  • IR2 749 events with the last at 1669 hours
  • IR3 111 events with the last at 1669 hours
  • IR4 2 events with the last at 1620 hours
  • IR 5 & 6 no events

Porsche advise the following:

  • The 997S red line is at 7300 rpm.
  • IR1 records revs 7300-7500rpm (Porsche advise events in this range, engine mechanical damage is possible)
  • IR2 75-7700rpm (damage possible)
  • IR3 77-7900rpm (damage possible)
  • IR4 79-8400rpm (damage probable)
  • IR5 84-9500rpm (damage very probable)

Events in IR1 could be classed as (over) enthusiastic driving, particularly in first gear and delaying the change after the rev limiter cuts in. This can produce events in IR2 & 3 as well. It is not recommended. If the car is covered by a Porsche warranty, any events in these ignition ranges would introduce a potential problem if there was a warranty claim. A special 'exploratory claim' would have to be made before Porsche agreed to cover any costs (but it has given them a reason not to pay the claim). The service shop would likely be asked to do a compression leak down test or a spark plug test for any events in the mid/higher IRs before any warranty claim consideration. If any issue arises within 50 hours of the over-rev event, it would be considered in this way (the last event was just 7 hours ago). In short, any events in the over-rev segments may invalidate the Porsche warranty at the manufacturer's discretion.

All the indications are that the engine has been worked very hard at or around its redline and for a regular everyday 911, this represents unsympathetic ownership.

The above note was written some years ago and thinking has evolved somewhat today (2014). Normally we would 'pass' an M97 Carrera engine with ignitions in IR1-3 and when there is a small spike (say up to 10 ignitions) in IR4, which were at least 75 hours previously, we would give the engine the benefit of the doubt. It is likely that anything negative that was going to happen, would have happened by 75 hours. Ignitions in IR5 and 6 still continue to require further examination in our view as damage probability increases significantly with such abuse.   Back

Oil change intervals

Q: Some time ago you inspected a Porsche 996 for me (which I purchased), I am considering selling the car, but have done very low mileages since acquiring the car, (less than 2,000 miles per annum). I would welcome your view on the "perceived wisdom" as regards servicing such a low annual mileage car. I had the vehicle fully serviced around the time I purchased it (Sept 06, 58k on the clock) and have had tyres changed, new battery, ignition coils, rear shocks etc done over the intervening years, but not another service (current mileage 63,500k).The garages say it should be done annually, but then they have a vested interest in saying so. There is a very minor amount of judder under breaking as speed, I've read that this can be addressed by having the rotors skimmed, is this advised (provided they don't fall below minimum spec), I understand that Porsche do this themselves to address the judder?

A: The engine oil on a 996 should be changed annually or at 12K miles (whichever happens first) and the oil should be changed even on a lightly used car. The reason is that in our damp climate the engine oil can only absorb so much moisture before it becomes saturated. Beyond this point there is a possibility of excess moisture in the engine accelerating corrosion or wear. The oil change interval was modified for the 2004 model year such that if the mileage did not pass 12K, then an oil change every 2 years was permitted.
The key thing about buying a used car is the condition. My opinion on the importance of regular oil changes on the M96 Carrera engine has hardened over the years. I believe the engine was not suited to the change to 2 year service intervals from 2004. An annual engine oil change would, in my opinion, make it less likely the engine will suffer from bore wear or IMS bearing failure. It is also a critical requirement that the cooling system is maintained at top condition. This may include a preventative maintenance change of the coolant pump after say, 5 years life and ensuring the blue reservoir cap is not leaking. Good oil quality affects so many items in the engine. Poor oil quality can gum up the hydraulic tappets also, producing a tapping that can be confused with advanced bore scoring.  Back

Intermediate shaft failure

Q: What has your experience been with Boxster intermediate shaft failures? A friend of mine is looking to get a Boxster, but is not too confident after reading and I am not too well versed on this particular failure.

A: A very small number of post-97-2006 water cooled 911s (996 and Gen 1 997) and Boxsters/Caymans have experienced intermediate shaft bearing failure. The failures appear to be confined mainly to the cars fitted with a sealed double row bearing (approximately 2001-2006). There does not appear to be a trend of causal factors other than the fact that the original bearings were not strong enough for the very varied use that Porsches are put to these days. I could say that bearing failure appears to occur on cars with 50K plus miles, but that is not conclusive. The bottom line is that this is a lottery and because it appears only to have affected a small percentage of cars (possibly 1-2%), you should not worry about it. Some specialists offer ceramic bearings in replacement which can be fitted at relatively low cost, particularly when the clutch is changed. The IMS bearing was strengthened during the 2006 MY. This means that some 2.7s may be affected, but the Cayman S should all be 2007MY cars. 2007MY 997s (including those late 2006 delivered cars with the 56 plate) should have the strengthened bearing.

This issue would not stop me buying a car, if it was otherwise on the button. Many independent specialists now offer strengthened IMS bearings to retrofit. Replacement at clutch change time reduces the relative labour cost involved and can improve the desirability of a car at resale.

For more info on replacements, I would suggest you talk to any good independent Porsche service shop.    Back

Cylinder bore scoring on 996/997/Boxster/Cayman

Q: Should I worry about bore scoring on a Gen 1 997 or Boxster/Cayman?

A: The reality of this problem is quite different than some (with vested interest in the repairs) would have you believe. There have been a small number of failures, but these appear to have been confined to the larger engined or powerkit models (997S, Cayman 3.4, 3.6 996 X51 for instance). It does not appear to affect so much the 3.6 997, the 320hp 996s, 986 and 987 Boxsters and Cayman 2.7. It does not affect the Turbo or GT models, which have a different engine.
Nobody argues that this engine doesn't have the reliability margins of earlier air-cooled engines, but correct service and maintenance, combined with thoughtful use can significantly improve the chances of a trouble-free ownership. This does appear to be an avoidable issue and should not put you off buying these cars. An understanding of the symptoms can save you a lot of money, either when buying or during ownership.
With wider Porsche ownership, and large scale availability, Carreras were clearly being heavily used as short distance run-arounds, in the way that the family Golf or school run car had been used previously. This includes continuous short, cold running (where the fuel mixture is rich and washes the bores), immediate pulling away after starting (preventing the oil from warming and getting to the critical protection areas), and not maintaining the cooling system properly.

The damaged cylinder bore warning signs to look for are an increase in oil consumption (where greater than 1000miles/litre is OK and less than 500 miles/litre begins to show a problem). In the developing stage of this higher oil consumption, a sooty left side (on a 911 the nearside in the UK) exhaust tip will be seen (indicating heavier oil consumption in cylinder bank 2 (usually cylinders 6 and/or 5). The exhaust tips will have an uneven colour when this happens as the right tip should be a normal chocolate colour. On the 3.4 Cayman S (for instance), the complete exhaust tip goes sooty. As the wear increases, there can be a light tapping noise from the engine's right side. This rises and falls with revs. Unlike say, a temporarily blocked hydraulic tappet, this will not go away as the engine warms. The tapping is the piston contacting the cylinder head or bore.

Hartech, a UK based Porsche specialist, researched the possible causes of bore scoring (and also cheaper repair options compared to an all new engine) and their conclusions suggested that a major factor could be inadequate cooling/coolant flow around certain areas of particular bores. This allowed certain parts of the cylinder wall to get much hotter, particularly when the car was driven hard. The tendency for the larger or tuned engines to suffer the issue is thought to be due to the reduced cylinder wall thickness or hotter running of the higher power engines. The extreme heat and variance in temperature around the bore could cause the liner to change shape (going slightly oval), or affect lubrication of the piston against the liner wall, with the piston hitting the wall and finally ending in a seized engine.
This situation was not helped by the new extended service intervals from the 2004MY, with the engine oil now having to protect the engine over a two-year or 20,000 mile (30,000km) period, rather than the previous one year or 12,000mile (20,000km) interval. The importance of engine oil changes makes a full service history even more important than before. Many experts now suggest a minimum annual oil change for these cars.
The coolant system is suspected as a contributor to this issue, in that the cooling flow to cylinder banks 1 and 2 appear don't appear to take into account the differing piston thrust faces - with the bank 1 (the left bank on a 911) receiving better cooling. It is thought any defect in the cooling system should be treated as a warning signal (as a reduction in coolant system efficiency directly effects cylinder bore temperatures). Check the reservoir (on the left of the engine bay) for satisfactory coolant level and that there are no leaks from the radiators (at the front of the car) or the blue reservoir cap (showing as a white crusty deposit). 
These failures are real, but we must emphasise that they are a relatively low percentage of all the Carrera engine Porsches out there. More than a few reputable independent dealers I have spoken to say that they haven't seen a bore scored 996/997/Boxster or Cayman for years (and that is only partly down to their expertise). It should not put you off buying one of these cars, assuming you do your homework and know the obvious failure signs.  Back

Early stage bore scoring identification without tools

Q: I am looking to change my 996 for a low mileage Gen 1 997 4S. I am mechanically very knowledgeable and I perform some work on my cars myself. I'm capable of listening carefully to an engine on startup, checking for smoke, sooting in the exhaust tailpipe etc etc.. My question is... if I do these checks on a 997 that I'm looking to possibly buy and everything seems to be in order and there is nothing that worries me, if you did the same thing on a car would that be 'enough' for you go ahead and part with your money or would you still do further checks, specifically checking the cylinder bores for wear?
If I have read your notes correctly I think you are saying that if there are any problems with the cylinder bores on a 997, there will be enough external symptoms to tell you that fact without needing to go any further. I suppose the question is if there are no apparent symptoms such as smoke, sooting, ticking, could there still be an issue with the cylinder bores but with no external symptoms? If just one cylinder bore has some light scoring would that be sufficient to show the external symptoms that you mention including sooting of the left tailpipe?

A: The invisible symptom of cylinder bore scoring in its early stages is a raised oil consumption. However, by the time most owners have realised their car is using a lot of oil, even if it isn't tapping, it will have left a sooty residue in the left exhaust tip. If the exhaust tips have been thoroughly cleaned, this is also a warning sign.
A poor service history means the oil can be saturated with water and this reduces its ability to lubricate in the cylinders. We always suggest on Gen 1 cars that they should have fresh oil every year, particularly if they are urban Tiptronics.
Evidence that the cooling system has very recently been overhauled or indeed has current issues is another early warning sign. Scoring is believed to be down to the front right side cylinders becoming overheated. They are at the end of the engine cooling circuit, so if the coolant pressure is reduced or the level low, the right bank cylinders get less cooling. On the larger bore engines (the 3.8 and 3.4) there is some evidence to suggest these go oval when overheated - resulting in the scoring.

Evidence of a poorly serviced cooling system includes leakage from the blue reservoir cap or leakage from the front flexible hoses coming from the radiators. These can be seen behind the front wheels in front of the steering rack. The clamps get rusty, relax and weep. You may need to jack the front up to get a good look, but a small camera can be used to get a view from behind the wheel.
A smell of coolant from the area of the front radiators is also a tell-tale. If we see any signs of scoring, we just tell the client to pass on the car. A borescope check may only tell you what you suspect anyway. Some dealers do this as part of their pre-sale prepping, which is a good peace of mind action and shows they are a responsible seller. Scoring can develop very quickly, within a few hundred miles.
The problem appears to have gone away with the Gen 2 DFI engine.  Back

Is a borescope check essential during an inspection on a 997?

Q: Is a borescope check essential during an inspection on a 997?

A: A borescope check does little more than tell you the condition of the engine at that point and it is easy to confuse normal cylinder wear with cylinder damage due to scoring. The unscrupulous can use such checks to justify the need for a major engine rebuild. In the right, experienced hands, it can be useful for estimating the rebuild cost of an already damaged engine without the cost of taking it apart for assessment. A good cylinder bore can be damaged in very few miles if all the contributing factors are stacked against it.
A borescope check does not need to be a routine check for any used 997. Using a borescope is an invasive diagnostic method that involves removing the right side heat shield and coil packs before removing the sparking plugs. In many cases, when the heat shields and coil packs are removed from a 10 year old engine, either the shield mounts or the packs will need to be replaced. It is also necessary to turn the engine over by hand to get the pistons at the base of the bores. Many service shops have heavily promoted the importance of borescope checks on every Carrera water-cooled engine, but it must be noted they have everything to gain from this, while most engines are not even at risk from the issue. We do not claim infallibility on spotting this issue, but we also err on the side of caution. It can be very difficult for anybody to spot if the seller knows how to conceal the signs.

It is our experience that unless the issue is concealed, the external warning signs discussed above are reliable indicators. If we see the warning signs, we tell you not to buy the car. End of story.
We would also advise you to beware of borescope checks being done by those who don't have the experience to separate normal cylinder wear marking (inevitable on any car with a used mileage) and actual cylinder damage.  Back

Gen 1 or Gen 2 997?

Q: I have begun researching with a view to purchasing a (997) Carrera S. I have a question about the durability and robustness of the Gen 1 engine. I would like to ask your opinion of the 05-08 engine as this could influence my decision to buy a late 997 Gen 1 Carrera S now or hold out for 997 Gen 2 to drop in to my price bracket. What I am effectively asking is, would even an apparently well cared for, correctly serviced and driven with mechanically sympathy 997.1 inevitably suffer a failure of the known modes discussed at length in various forums etc?

A: If it was me, I would hold out and go for a properly serviced Gen 2 car. The 2007 model year (Sept 06 onwards) had stronger intermediate shaft bearings and that appears to have solved that issue, but the early Gen 1 cars in particular (05-06) seem prone to cylinder bore scoring, especially when the servicing/care is intermittent. We think it could now have affected up to 10% of the Carrera engined cars (as at Nov 2014) - and that impression has risen from 5% perhaps 2 years ago. That said, the forums are filled only with those who have had the problem or those who have everything to gain by painting as gloomy picture as possible. There is a serious shortage of expert opinion on the whole picture.
Bore scoring may be related to the design of the cooling system, not enough engine oil changes (2 years is a very long time for a complex engine) and even poor quality fuel. It does appear the engine wasn't robust enough for the changing use that today's Porsche drivers put the car through (school runs, short journeys, short periods of excessive engine revs, etc). The symptoms though can be spotted without intrusive inspection, but beware of normal cylinder wear being mistaken for more serious scoring.
Either way, the 09 onwards direct fuel injection engine was a completely new design and so far, there haven't been any solid reports of trending major issues.   Back

996 Over-rev events

Q: Are over-rev events applicable to a 2003 996? If so, are the 997S guidelines (as per the article on 997S over-revs above) applicable?
From what I gather, the risk of bore scoring on pre 2004 models is much reduced - would you agree with that?

A: Yes, the over-rev events are applicable to all 1997-2005 996 models. The 996 records only 2 ignition ranges, with IR1 being revs in the red sector of the tacho and IR2 being mechanical over-revs that require more explanation.

This is how we explain it in our inspection reports:
The 996 ECU records the over-revs as spark plug ignitions (so 3 ignitions for each full turn of the engine) in two ranges; Range 1 is between 7300 and 7900 rpm and Range 2 is over 7900 rpm. It also records the last occasion the revs were at that limit (in the total operating hours). In effect, range 1 can be hit by driving the car hard and taking the revs to the maximum (red line).

It is not that easy however, as the IR2 do need interpretation, particularly how long ago the last event happened. If the IR2 recording is what appears to be a single spike and it happened hundreds of hours ago, most experts would give the engine the benefit of the doubt and OK it.
Bore scoring on the pre-04 cars should not be an issue. IMS bearing reliability is thought to have affected only a very small percentage of the 2000-2006 Carrera engined cars out there (911 & Boxster/Cayman). Service history is critical on these cars and those that have had regular annual oil changes seem to be in better shape. Back

C16 or C98?

Q: I am looking at a 997 RHD that has been imported from Cyprus. The vehicle has a replacement service book. Therefore this is no VIL label, but I assume the country code is C98 rather than C16. Should I be unduly concerned about this?

A: I would suggest this is probably OK. Several leading independent dealers used to bring in C98 cars from Sweden or Cyprus to get round the long waiting lists for 911s that existed a few years ago. Porsche GB will not have the car on their books, but all the initial manufacturer warranties will have expired except the 10 year bodyshell warranty. Unless the car has been driven on a beach or similar, that should not be a problem.

The official dealers are nonetheless very willing to look after these cars and there is no fundamental difference between a C98 and a C16 except perhaps it may be programmed to accept lower grade fuel. The option spec of these cars is often better than the UK versions but it is important to check they have things that were standard on the UK cars (alarm/immobiliser, full leather, etc.

The difference in values between a C16 and a C98 tend to disappear after about 5 years. There is anecdotal evidence official network sold service books with REPLACEMENT stamped all over them to increase the value/exclusivity of their own cars (which it did).

All I would say is that these cars are very easy to clock and its worth having a professional with a Porsche diagnostic computer (such as PIWIS or Autologic, Durametric won't do it for pre-Gen 2 997s etc) look at the ECU to compare the DME mileage against the mileage on the dash. The computer would also look at the history of engine over-revving (any trackdays?) and also the engine/accessory system fault codes.   Back

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