Scored cylinders... and now rebuilt!

[James_W]

Chaps - looking for some advice if possible?

Model :996 Carrera 4S
Year: 2004
Modifications :None
Mileage: 55,000
Type of driving: (road/track etc) 18k p.a and couple of track days planned
Current oil used (brand and viscosity) Shell Helix Ultra 05/40

As some of you are aware I've recently taken ownership of the above (about 3 weeks ago) and having already racked up 2000 miles have noticed it is using approx 1 litre per 1000 miles - my understanding from speaking with a couple of independant specialists is that this is within the guidelines from Porsche.

- The engine has no leaks, is totally dry underneath, but there is some fairly rapid oil emulsification build up in the filler neck.
- Blows blue on ignition and the clears quickly (perfectly normal for the engine type).
- Doesn't blow smoke under normal driving, however, on kickdown I noticed a plume come from the passenger exhaust which vanishes when ease of the gas.
- There is more coking on the passenger exhaust pipe than the drivers side.

One indy (Strasse) test drove it and suggested I have nothing to worry about but should monitor oil usage and the other RPM Specialist Cars (North Yorks) have suggested the oil separator may be on its way out, although checked the throttle body which had no traces of oil...

I am concerned about the exhaust plume under heavy acceleration and the rate of oil consumption..

Would changing to a 10/40 slow down the rate of oil consumption? What recommendations could you make or thoughts re the symptoms described above?

Yours,

Percy Paranoid 

 

[Richard_Hamilton]

Personally, I think 1L/1000m is fairly high consumption for a 996 Carrera. On my old 1998 C2 I never had to top up between oil changes (6000 miles), and the level gauge would drop only 1 or 2 bars at most. Although what you are experiencing is within Porsche limits (1.5L/625m) I think it is a bit on the high side. I don't think 10W-40 will make much difference, as the hot viscosity is the same. I would go for a 5W-50 (Mobil 1 if you want an Approved oil) to see if it helps. Don't worry about the mayo in the filler tube - it's normal, especially in this weather.

 

[James_W]

Thanks Richard - so do you think I may have a more sinister issue to worry about? What tests should I have done to see whether the engine is using up the oil? Do oil separators give warning that they may be abut to fail (such as I've described)?

 

[Richard_Hamilton]

When the AOS fails you get huge clouds of WHITE smoke. Also, you get the tell-tale oil in the throttle body, which you have chacked for. I would try the 5W-50 and see how it goes. Sorry to sound a bit negative. If you really want to put your mind at rest, then the only way of checking the condition of the piston rings is to get a cylinder leakage test done.

 

[James_W]

So... Had the car inspected by Hartech who carried out cylinder pressure tests - all good at 250psi... Also did a camera endoscopy on all six cylinders. There is piston scoring in 4,5 & 6 - hence burning oil and smoking from passenger side exhaust. I bought the car from Redline who have since had it also internally inspected by Strasse who they use for servicing. Strasse have confirmed the worse and have recommended either a new engine or: - pair new crank cases - new pistons - new timing chains - new big end - new main seal - new gaskets - new anything else that's required upon inspection of the original engine... The good news from my perspective is that I only bought the car a month ago and Redline are being very supportive in paying for this work and hence the refurb route. Is there anything strengthening modifications I should request? Thoughts? James

 

[Richard_Hamilton]

If you can get Redline to agree to Hartech doing the work, then I would get them to fit their liner support rings and strengthened intermediate shaft. It woul make the engine virtually bullet-proof, and probably add desirability come sale time.

 

[James_W]

Strasse are currently totally rebuilding my engine with new crank cases from Porsche UK, pistons, timing chains etc. My understanding is that all new components will be warrantied for 2 years. To introduce the Hartech mods to a new engine crank case will invalidate the warranty from Porsche - hence not really an option at the moment. Photos of the cylinder creep scoring in old cylinders 5 and 6 - it is clearly visible that the cylinder cooling channels around the cylinder lip are missing any kind of strengthening... a clear design flaw which allows the cylinders to go oval over time which in turn means the Lokasil piston finish degrades causing debris and scoring of the cylinders.

 

[Richard_Hamilton]

Looks nasty, but I could not see the logic of replacing the crankcase, pistons, and timing chains etc. Those parts, plus gaskets, etc, will come to over £5000, plus about 40 hours labour (say £60/hour). Say £7500 plus VAT. I say "could not" because until reasonably recently an exchange engine for a 3.6 Tip was £5500, ready to fit including all ancillaries. I just looked up the latest price. £9834.18 +VAT. I wish I could jack the prices of the bits my company makes at that rate.

 

[James_W]

Agree Richard - seems as though Porsche must be seeing less claims of this nature and hence have put their prices up! We explored the feasability of an exchange engine, however, it would have meant me stumping up a few thousand extra which I din't want to and hence the rebuild route. Called in at Strasse yesterday and Chris is well on with the rebuild now - looks like the engine will consist of virually all new components (exc. crank and a few other items). They have fitted 6 new pistons as the Lokasil finish is degraded on the pistons in cylinders 1,2 & 3 as well as 4, 5, 6. New IMS bearing and RMS and have requested they fit a new oil separator instead of the old one that's on the picture below whilst the engine is out. Am really looking forward to getting it back now - should sometime next week.

 

[James_W]

Just picked up my C4S from Strasse this afternoon after it's two and a half week engine rebuild. As expected it is running perfectly and has about 90% new components including IMS bearing, RMS, AOS and six new pistons and crank cases and one new radiator... I really rate the service I received from both Strasse and Redline in getting the problems sorted out. Just need to be gentle for the next few hundred miles or so and monitor the fluids carefully! Bring on summer!

 

[Richard_Hamilton]

Sounds like you had a good result in the end. You might find the oil consumption is a bit higher than normal (but nothing like your previous figures) until it has done a few thousand miles. But you can relax and enjoy it now!

 

[James_W]

Yes - an excellent result and a lot learned. I'm now really confident in the knowledge my car has essentially had a thorough going over from the brakes upwards and that all new parts carry a two year Porsche warranty! Just been out for spin on some of Yorkshire's finest and am loving it! Cheers

 

[kasspa]

Hi James, Glad to see you are back on the road & have been well supported by your supplier.... Regards Paul

 

[James_W]

Thanks Paul for your thoughts over the past few weeks - look forward to meeting Richard and yourself at the Modern event in May! James

 

[ashley]

great news James glad its all worked out