Engine rebuild - second time...

My engine is in Hartech, stripped and I have a diagnosis... but first the history... I bought the car from an ad on this forum. The PO had to rebuild the engine due to a dropped valve seat in cylinder 3 at about 114k miles. I have the invoices for £10k http://911uk.com/viewtopic.php?t=98339&highlight= I bought the car 2 years ago with 120k miles as it had a rebuild and good history with 10 owners. 50k miles were put up in 18 months of what looked like commute between Birmingham and Sheffield! it has been great for the past 2 year - I spent a few grand on suspension and tidying bits and pieces - but recently I became concerned about a coupe of things - a bit of smoke on start, a tappety sound and fluffy idle when started. On the evening of the 26th April I took a mate for a blast. He was impressed at its performance (first time in a 911). I told him I needed to check out some things but that yes it was pulling well. We stopped off at another mates house for a couple of hours and then when I started the car it was really rough. Took about 30 seconds for the idle to settle. But once warmed up, I floored it in 3rd and it took off like a scalded cat. No problems. When we came off the motorway, we drove for about 2 miles to his house. I pulled into the drive, he hopped out, I put the car in reverse and immediately there was a bad rattle, so i shut it off. I started it quickly again to check oil pressure and see it if was engine related and shut it down immediately. Oil pressure was fine. I rang my car insurance recovery and they took me home within an hour. I started frantically reading on here and on the www and reckoned it was either timing chain issue or borescore. My car insurance rang me in the morning to see if I got home ok. They asked if I had any questions. So I asked if they would still take me to a garage and they said yes. I asked did that include a garage in the UK (I'm in Dublin) and the nice lady said she'd check with a supervisor. What she came back she asked why I couldn't go to a garage in Ireland, so I told her we didn't have the technology or experience and that while I could get the engine removed in Ireland, we would have to send it to the clever people in England - and so she said yes! I then called Hartech and they said they could take it but couldn't start on it for a few weeks. So on Thursday 2 May the nice man in a truck came and took my car to Hartech free of charge and saving me a packet.i didn't even bother pulling a filter or looking underneath. The engine is finally disassembled and I have the diagnosis. And it isn't bosescore or IMS.... It's another bad valve seat in Cylinder 2 - the neighbor of cylinder 3. Grant reckons that it can only be due to an over heated head or a bad valve seat batch. I don't have any history that would suggest an overheat. Regardless, Hartechs advice is not to use the same head again unless the 12 valve seats are replaced and this is not something they have found an acceptable solution to. While some people will replace the seats, no of them seem to be providing warranty to protect Hartech in the event a seat fails again. So where do that leave me? A full rebuild plus either a new head (£3,500) or a good used head... which seem to be like hens teeth. If anyone has one lying around, please PM me. I have a feeling that any good used ones are in Mr Corns garage! I'm happy to go with Hartechs position on the head as lightening has struck twice in my engines case. I'm coming to terms with the cost implications. I'm also a bit peeved that the cost of the head has killed any chance of a 3.9... So there you have it - 127,000 miles, 2 rebuilds and not a sniff of borescore or IMS issues... I did contemplate selling it as is, but then I'm still faced with replacing it and doing all of the work I have done already and still have a risk on the engine. And based on the recent threads here, there aren't many good ones around. Part of getting the wife across the line was telling her we can do a weekend in the Lake District when I pick it up from Hartech...I just need to figure out a way to break it to her that the budget doesn't cover a hotel and that we'll be sleeping in the car.

Sorry to hear that, you are right about the heads though. 3.4l heads are rare, but 3.6l ones are like rocking horse poo. That is one reason we are concentrating on the 3.4l heads for our project. I'm afraid I don't have any 3.6l heads at all. I was talking with another specialist a few weeks ago, and they had seen a spate of dropped seats recently. Very odd. What is the internal damage like? MC

Piston and cylinder 2 are beyond repair and some damage to head. Debris seems to have spread to other 5 cylinders and superficial damage to piston coatings so they need to be replaced or repaired and recoated. New ones are circa £500 each. Costing doesn't work with lokasil cylinders so decorating pistons will force new cylinders, but still cheaper than new pistons. I'm cool with new cylinders. The Previously replaced number 3 is steel, so I would need to replace it and number 2 anyway. Nothing else catastrophic. One cat breaking up. Clutch and flywheel need doing but I expected that. Brake pipe over the gearbox etc. you know from your experience!

obviously I am sorry to hear this and feel your pain but at least its just the first rebuild you are paying for, I've not heard many stories of dropped seats yet so maybe age is getting to them?

Sorry to read the bad financial news, I hope it's back on the road soon. I've no idea what a valve seat is, but can they be 'future proofed' along with other bits as part of a general rebuild? Or is it a luck of the draw thing?

The valve seat is a steel piece inserted into the alloy head casting that the valve sits/seals against. If there wasn't a seat, the steel valve would bash the alloy every time it closed and it would wear it down. On most engines the valve seats can be replaced - and they can be on the 996 too - but because there are 4 valves in very close proximity, and the is limited alloy material in between them, replacing them to a level of engineering that is as good as original doesn't seem to be available at the moment. Hartech have investigated but can't find anyone that will do it. That's my paraphrased understanding anyway based on what I've been told. And while I'll happily question Hartech, I'm not going to second guess them. Thanks all for the replies. Am I the first owner to have a 996 with 2 rebuilds for the same reason? Might I be eligible for a prize. :?: like a free head

Yes, you get a third failure for free. Although I am sure there are a few that have had a couple of IMS bearing failures in the same engine, especially when they have " upgraded " to an aftermarket type solution

:floor: :thumb:

Never good to see a post about an engine failure but good to see your sense of humour has survived the ordeal so far.

Nothing much to add really other than I'm sorry to hear this OP. Frustrating, especially coming from a car that should have been pretty solid with a rebuild. Interesting to note too that it's neither of the 'main" culprits that caused the failures.

Have you (or Hartech) contacted Porsche about this? They do 'recon' blocks, maybe they could do a recon head too? The cars are old now but they may help and there's nothing to lose, it would certainly be good to bring the problem to their attention.

Really sorry to hear of the issue you have suffered, doesn't seem fair as you have followed a sensible approach when buying..... Am being a bit ignorant. But you mention a bad valve seat as the culprit. Then mention damage to the bore/piston and contamination of the other cylinders. Was wondering what caused this collateral damage Did the seat (or part of it) break away from the head, or did the valve stick as a result and get broken up? You seem to be taking a very pragmatic approach to this. I hope I can approach things in a similar way when something like this befalls me. Am always on ebay etc, so will keep a look out for any 3.6 heads I see. I think you have made the decision to change hears, rather than new seats.....I think that makes complete sense.

A bit of valve seat came off and hammered around the cylinder damaging it and the piston. Some how debris got into the other cylinders - possibly getting past the rings on number 2 - and contaminated the other cylinders. I spoke to porsche this morning - only new heads on offer. They don't even offer a complete engine anymore - discontinued. Only short engines (they don't include heads). I thought if I could get a complete engine and part it out, it might be more cost effective than buying just the head, but it isn't possible anymore.

Sounds like very, very bad luck on a number of levels. Might it be worth keeping an eye out for a used engine, using the head and selling the block, crank etc? Or is this usually only possible on an exchange basis these days? Or using MisterCorn's methodology, could a 3.2 Boxster S head be modded to fit, to give a bit more scope of finding one...

A long time ago I had a 914 2.0 on which one of the pistons broke up. The bits found their way past the inlet valve, back up through the inlet manifold and into two of the other three cylinders!