987/997 IMS problem fix Direct Oil Feed?

[impactbumper]

Originally Posted by masraum

So, if I understand you correctly, You're saying that the early engines had a certain percentage of failures (just to pick a round number, lets say 5%). And then the last couple of years had an update that drastically reduced their chances of failure (lets say 1% or maybe .5%). Then I think we can all agree that as of 2009, there's 0% chance since there is no IMS.

Right on the money (numbers being "lets say").


Furthermore, and this might start a controversy but I have to say the 3.6 motors are less prone to failure than 3.8 (997 generation, revised engines).


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[DWBOX2000]

Change the wAterpump and aos at 50k and drive on. Most Porsches have had problems over the years. The 1800 to replace the ims is a lot cheaper than most of the other porsche problems. My memory is lacking but I recall head studs, thermo reactors or something, exploding air boxes, plastic stuff in the metzger bullet proof motors to name a few. Other people have argued this point extensively. I am not enough of a motor head to give specifics but I have read enough that i believe there is lots of truth to this argument.
David

[Deschodt]

Originally Posted by impactbumper

Furthermore, and this might start a controversy but I have to say the 3.6 motors are less prone to failure than 3.8 (997 generation, revised engines).

I don't think that's controversial at all - that's pretty much what all UK Porsche magazines reported as well ;-)

They (I think it was 911& Porsche world) had a series on the IMS issues a while back... Pretty much mirrors what was said in this thread. More frequent on M96 (but ironically fixeable pre-emptively), somewhat less frequent on M97 (but not really pre-emptively fixeable for a reasonable $, since case must be split), the issue is more prevalent with S than Base models it seems, also more prevalent on cars that were babied too much vs cars that were driven hard but maintained properly. That's from memory now...

We've been there before in other threads, it comes down to risk aversion. Yes the risk is probably low, but I just *know* I'd be the unlucky one ;-) Given the approx $25K bill (maybe less if using an independent?) for a new motor, now that Porsche is done with courtesy repairs and discounted remanufactured engines, buying a more expensive 09+ makes sense if you are worried about it.

If however you live a charmed life, buy a first gen and cross your fingers. There is also a very small subset of 997.1 which have an M96 engine, but nobody can pinpoint an exact VIN# to determine changeover to M97. I've seen one at a shop, getting an LN IMS, I'd have bought it if it was FS ;-)

The irony is that for a while 996s were in the dump price wise, but now you can fix them (bearing in mind the LN fix also has a limited shelf life of 40K miles if I recall correctly), so they are going up in price. 997.2 are staying high because no IMS at all...
It's now just the 997.1 in no-man's land, until some clever person figures out an IMS fix for them that does not require a case split. I heard something was in the works... haven't heard since...

[masraum]

Originally Posted by Deschodt

It's now just the 997.1 in no-man's land, until some clever person figures out an IMS fix for them that does not require a case split. I heard something was in the works... haven't heard since...

What about the oil injection from my original post? If you do it preemptively, you don't need to remove the factory bearing. The "fix" in my OP seems like it's ideal for the motors that require that the case be split.

[LEAKYSEALS951]

Originally Posted by masraum

What about the oil injection from my original post? If you do it preemptively, you don't need to remove the factory bearing. The "fix" in my OP seems like it's ideal for the motors that require that the case be split.

I thought about this briefly when I owned a 2006 997s. At the time, the 911 and porsche world (or whatever article it was) was still open on the internet (It has to my knowledge been closed.) In it, was a tirade of customer reports of IMS failures (at the time- boxster, 996, 2005 997, etc. Also, in it, were the scored cylinders on the 3.8 997S engines. Higher than normal oil consumption, an oily diarrhea from the exhaust, kabamm!!!!

Between the unchangeable IMS and the cylinder scoring (and impending symptoms of oncoming scoring=very high oil consumption) I dumped the car and got eventually got back into an aircooled 911. (The 997s I bought had high miles and burned significant oil- made all the more frustrating by the lack of an honest to goodness dipstick to monitor!)

So- to make 2006-2008 997 3.8 work (for us tinkerers)- make a pressure fed system for the IMS, and address the cylinder scoring. Someone will. It might require a full rebuild with new pistons and IMS mods- but someone will. A good example is the inner plastic seal on the IMS bearing with a pressure fed fix. I guess you "could just punch it into the engine and hope it disappears", but addressing it in a rebuild would be better.

I think the long term issue/question for 2006+ IMS is this: Is the oversized bearing strong enough to a point where the majority of engines need an overall rebuild due to mileage before the enlarged "hail mary" oversized IMS fails? It so, it is a success. If not, I look at it as a $14 bearing that needs an $18,000 rebuild to replace it, assuming the pistons don't scratch the bore first.

Overall, I am optimistic. These cars really are nice. It will happen in time. Until that time. I would replace the broken headstuds on my 78 SC any day over dealing with that stuff. Why? Because I can. As a backyard redneck mechanic, I can. Not only can I replace them, I can replace them cheap. New studs, new seals, new cams, and I am in like flinn. Do I want to? No, but I have a contingency.

I also remember- at the age of 14 or so, reading magazines (panorama? maybe) on failing 944 timing belts. At the time it was more complex than an impending Y2K. In time, I owned several 944's, and replaced those $7 belts with little concern or effort.

So too will a solution for the 2006-2008's (or any waranteed motor replaced with an oversized IMS) come into play! I can't wait!

[speeder]

Originally Posted by masraum

So, if I understand you correctly, You're saying that the early engines had a certain percentage of failures (just to pick a round number, lets say 5%). And then the last couple of years had an update that drastically reduced their chances of failure (lets say 1% or maybe .5%). Then I think we can all agree that as of 2009, there's 0% chance since there is no IMS.

2009s absolutely have an IMS, as do all 911s ever produced since 1965.

[dtw]

Originally Posted by speeder

2009s absolutely have an IMS, as do all 911s ever produced since 1965.

Can't remember what year the 997.2 engine debuted, but I think it was 2009. That engine did in fact delete the intermediate shaft altogether. The cams are driven directly from the crankshaft.

[masraum]

Originally Posted by speeder

2009s absolutely have an IMS, as do all 911s ever produced since 1965.

https://www.oregonpca.org/resources/ims-bearing-the-full-story/

the M97 engine was retired and was replaced with the 9A1 engine which features improvements such as direct fuel injection and more notably, the lack of an intermediate shaft or IMS bearing.

[masraum]

Some interesting info in the article. There are some typos, but if you can read around those...
Apparently, the article is a write up from LN Engineering. I guess that means that I trust some of the facts, but then I'm also cynical about someone that sells a product writing an unbiased article.

The intermediate shaft found in the M96 and later M97 engine was revised three times. The earliest design incorporated a dual-row ball-bearing used through model year 1999 and in some 2000 and 2001 models. Starting in model year 2000, Porsche began phasing out the dual row bearing and went to a smaller single row, with significantly less load capacity. From model year 2002 -2006, all engines used this smaller, lower capacity bearing. Starting with the 2006 model year, the design was again revised to use a much larger single row bearing with the same load capacity of the early dual-row ball-bearings. This bearing increased in diameter, which increased the bearing and ball speed, further improving the bearing. However, starting with the 2006 model year, Porsche in its third revision of the intermediate shaft bearing, changed over to a design that is not serviceable, leaving later model years with no recourse for addressing this issue with preventative maintenance

The [Mezger intermediate shaft] design has been retained with the watercooled 996 Turbo, GT2, and GT3 models as their engines are based off the same 964 engine case with the same internals as the earlier aircooled engines. This intermediate shaft features plain bearings (no ball bearings) that are pressure fed engine oil for lubrication and never fail.

Unfortunately, due to how the crankcase was designed, there are no oil passages from which pressurized engine oil can be used to lubricate a plain bearing on the side closest to the flywheel. The IMS in the M96 (and subsequent M97) engine is located directly beneath the crankshaft carrier and is connected to the crankshaft by means of a chain. The IMS has a sealed ball bearing on one end (closest to the flywheel) and a plain bearing on the other end, which resides in the oil pump/coolant console. Additionally, it is this ball-bearing that handles the majority of the load on the intermediate shaft.

According to information published about the Eisen IMS Class Action Lawsuit, the single row IMS bearing used in 2000 through 2005 model years is reported to have an 8% failure rate, versus less than 1% with the dual row IMS bearing. The 8% failure rate cited by the settlement documents is not far off of the calculated L10 life LN Engineering has been using for the last five years! With half the load capacity, it is clear to see that the reduced load capacity of the single row IMS bearing is a significant contributing factor to the increased number of failures.

[speeder]

I stand corrected, did not know this. I'd love to see how they did this in that engine design.

Of course, Mezger and all other 911 engines since the beginning had intermediate shafts.

[rusnak]

^Yes, that Oregon PCA arcicle was the exact same one that I read before pulling the trigger on my '11 Caman with the 9A1 engine. Oil consumption has been nil, and it's a fun car.

One weird thing about it is PASM. When hustling it around a corner, you expect to kick the rear end out a bit and expect the apex to be where you know it should be, then PASM kicks in and scoots you about 8 feet to the inside. It's really odd the first few times it happens. It feels like sitting on a chair on linoleum, and having someone scoot the chair to one side.

[gtc]

The fact that LN now recommends replacing their ball bearing IMS retrofits every 75k or 6 years suggests to me that a 5% or even 8% failure rate for the stock bearing is too low of an estimate.

I have a buddy who's "fixed" IMS failed. I suspect we'll see more. As much as I would love to tinker with a cheap boxster, I'm not willing to take the gamble.

Also, we haven't even mentioned all the other ways in which these engines fail.