Just the usual, 996 engine rebuild

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Two weekends ago, started up the car, huge cloud of smoke the day before it's MOT. Obviously no point in going for the test, the fact that the road was engulfed with a smoke haze akin to downtown Beirut pointed to the fact that it was unlikely to pass the emissions element! Luckily, the mechanic I use for the girlfriend's car happens to build Subaru race engines so was more than happy to give it a go to at least try and diagnose the problem. So, for a few days last week, in-between other work, he took out the engine and gearbox and began to strip it down.

AOS looked fine so that was discounted and a visual inspection of the cylinder heads showed up nothing either. So there was nothing else for it but to split the case. The only thing that was awry was a split seal on one of the pistons. Have the sent the case away to check for ovalisation but visually it looked fine and the bores perfect. Happy in that all the worse case scenarios seem to have been avoided but a bit gutted that one seal is going to, in all likelihood, end up costing about £3000. I am now on the shopping list of parts to make it worthwhile on the labour front. This poses a few questions as to what exactly I should replace so all help or suggestions appreciated please:

Clutch plate and clutch bearing
Low temperature thermostat
Complete Seal and gasket kit
RMS seal if not included in above
IMS bearing - thoughts on supplier? European Parts Solution via Design 911 or LN Engineering?
Air and Oil Separator
All three timing chains
Full service kit, including Spark plugs

Anything else glaringly obvious I have missed?

Thanks in advance, Rich

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Thanks for the replies, it's a 2002 model 3.6 but has done 172,000 miles (106,000 done by me on the motorways of the UK) so the Hartech route makes it all a bit uneconomical if I'm honest. That is likely to push the bill nearer to the value of the car and luckily for me, the missus is of a view that it and the Karmann Ghia need to go to get a newer 911! Unfortunately I have missed the boat in terms of a GT3 etc but still plenty of nice motors around.

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Thanks MTR but the missus has seen a blue 997 and whilst maybe not this particular car, it will be a 997 in blue!

Not sure if oil seal is the right terminology Bert but on the piston, there is a lip and sitting underneath the lip is a seal and it was this, on one cylinder only, that a piece had separated. Hope that helps, may even try and take a photo this week.

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Moosh said:

Did the smoke continue when you drove off or did it stop?

It stopped after a minute or so, initial thought was head gasket and it was burning off water but this was definitely oil based smoke. No coolant contamination in the oil, no fragments in the oil when we drained it off and nothing on the sump plug/strainer.

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Moosh said:

after the smoke stopped did run okay

Yes, although I only went 20 mph back from the garage but seemed fine; wasn't hunting or misfiring and no loss of power that I could detect but I didn't floor it. No warning gauges and temperature was it's usual self

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Great news over the weekend, absolutely nothing wrong with the engine casing, no delamination of the bores and ovalisation is absolutely minimal. Cylinder heads also had a clean bill of health, no cracks or warping so a skim and the valves need to be re-seated. Final bill is going to be a few thousand due to the likes of the new IMS, RMS, AOS, clutch plate, clutch bearing and timing chains etc. All in all, a fair amount of relief. Did take on board the view of sending it to Hartech but really can't justify that economically with the mileage it has. Just glad it's not off for scrap. Both engineering shops are happy to provide reports of their findings for peace of mind.

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Tap450 said:

Might sound silly but are you sure it's not just abit of oil sat in the bore? Has it been using any oil? The flat engines do smoke on start up some times when there's oil in the notes from were it's been stood?

The only thing that found was a piston ring/seal that had split; everything else has passed the check! Not sure how much one is, but it's resulted in a large bill but could have been a whole lot worse!

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Definitely sure, there is smoke and there is something akin to a pall of smoke from a live firing range! Anyway, bit too late now as it's in a million pieces in the garage awaiting a shopping list of parts... The seals and gaskets from Euro Car Parts are £464 before anything else.

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c4sman said:

This thread kinda supports my theory that all m96 owners are not crazy as their engines are not all about to implode. 172k miles on a high performance engine sounds pretty good to me and even now the problem is not catastrophic. Sorry that the OP is having to shell out but sounds as if you've had your monies worth.

I've done 106k miles in just under five years, come rain or shine and this is the first major thing. Admittedly, most of those miles have been on the delightful A3, M3 or A34 but even so, it's been bloody fantastic. I have serviced it regularly and apart from this, there has been the usual coffin arms etc and a sheared water pump which again, coasted to halt on the motorway, be the butt of everyone's horns as they drive by but didn't try to get to Membury services and all was well!

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m444ttb said:

That sounds largely like good news to me! Grant @ Hartech just called about mine following its strip down. Lucky i was prepared to spend lots of money as I was about to have very little choice. Crank bearings just down to the copper and an IMS bearing that could have self-destructed at any time.

It's very good news, ok, of course I could have done without it but with an upgraded IMS bearing, clutch, timing chains, seals, gaskets and AOS then it should be good for a whole lot more miles yet. The engineers couldn't believe the lack of wear given the mileage and is certainly testimony to the merits of Mobil 1 in my mind. Hoping yours is equally successful.

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All the spares have either arrived or on their way except for one thing, the IMS solution. The more I read, the more confused I become (which isn't the hardest thing in the world admittedly), so it appears the options I have are:

LN 106-08.2 which seems to be popular although considered expensive and is recommended changing every 40,000 miles;

European Parts Solution which is a lifetime solution but seems to be a bit of an unknown quantity; or

replacement Porsche part if available.

My original IMS looks from the outside to be in good condition but of course, internally there has to be a lot of wear. Any considered advice would be appreciated.

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griffter said:

There are also oil fed ims bearing solutions. It's an interesting dilemma and I don't know what I'll do when the time comes.

Me neither, unfortunately my time has come!

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Scockers said:

I agree. Sounds normal.

Thanks everyone, but unfortunately it is used everyday come snow, rain and shine and it was an inordinate amount of smoke; I've seen less on a firing range!!

Just collecting all the parts, new clutch etc but still stuck on what to do with the IMS bearing but will explore further the bearing change. Only downside is all the prevaricating means the timelines are slipping to the right.

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Tap450 said:

If I was you I'd change it while your there. Iv seen one go last week and they course a lot of damage. And you will be back to square one saves you a lot of hassle and money. I'm sure you can get a ceramic one but I'd go and buy one from your local Porsche centre

That's what I've done, couldn't really find a satisfactory remedy that I was convinced by, especially with the amount of miles I do I would be changing the LN one every 18 months!

[sm34uk]

Long story but when we took it into Porsche, they said they only replaced the housing but not the bearing and they were absolutely insistent on that. Strangely the one they supplied, for a 3.6 didn't fit, the nut was 15mm and mine 18mm-19mm. The part on mine was from a 997 so the only explanation has to be it has already been done; but Porsche couldn't explain it or have a record.

Anyway, the engine has now been put back together and is absolutely awesome, just have to run it in now. Not had the final bill but am pretty confident it should provide me with another 170k miles and am looking forward to taking it to Regal when it's run in to see what it is delivering on the rolling road. I was fortunate enough to win a competition in Total 911 for an EVOMSit re-map through Regal. It was measured at 310bhp before and 316.5bhp after so will be interesting to see what it is now. Early days but very promising. Even if there is no change, just having a new clutch and fly wheel will improve the feel immensely.

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Now for the difficult part of running it in; been a long time since I have ever had to do that but worth it given the outlay. Difficult part is not giving it any right foot! Engine seems really strong so far but not taken it near to 4000 rpm let alone any higher. Doing about 100-150 miles before changing over the oil. So far, all the signs are good and I am very pleased indeed.

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hartech said:

The original 996 single or double row bearing would have had an 8mm thread and a 13mm nut (across flats).

Various replacements had changed the internal bearing and the spindle (as indeed ours did) to a 10mm thread size (the originals were too flimsy) and the nut size for that is 17mm (across flats).

The later large bearing IMS has a 12mm thread size and a 22mm nut (across flats).

The only conclusion from this is that your engine had a modified non Porsche spindle fitted either as a job with the engine together (in situ) or during an engine rebuild (when it was apart).

The assumption then is that it also probably had a new bearing of some sort. Not sure exactly what you mean by a "housing" but would be interested to find out. Perhaps it was fitted with a different "spider".

Perhaps the engine had already been rebuilt once? have you checked the engine numbers to work out the age of the engine (they come without numbers so if none are present it was a replacement not stamped up but then I would have expected it to have the standard nut or larger bearing nut - neither of which it had.

Baz

Hi Baz,

spoke with Dan who rebuilt the engine and from his memory it was the 17mm nut size attached to the housing (that was the term Porsche used) but is in all likelihood the three legged spider to which you refer. Certainly the first nut that Porsche supplied was far too small so a much larger nut had to be supplied but was from the 997 part numbers.

I will have to go through all the old invoices from Porsche to see if I can find any reference to the engine being rebuilt as they were at a bit of a loss to explain as to why the 997 part was on there.