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YOUR RESEARCHEngine rebuild after IMS failure
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Install incorrectly
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Performed · outcome unconfirmed · Original poster
My shop believes that the replacement bearing had to be installed incorrectly to fail so early, but it is also clearly an inferior one.
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Performed · outcome unconfirmed · Original poster
I had the work done as part of the purchase and the shop who sold the car told me that they installed the LN Retrofit bearing.
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Performed · outcome unconfirmed · Original poster
Since the intermediate shaft had to be replaced, we just installed the Porsche bearing that was included for now.
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Performed · outcome unconfirmed · Original poster
The invoice just mentioned "IMS bearing replaced".
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Performed · outcome unconfirmed · Original poster
Since the intermediate shaft had to be replaced, we just installed the Porsche bearing that was included for now.
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So my 3.4 engine failed 1.5 years and around 8000 miles after the original IMS bearing was replaced. I had the work done as part of the purchase and the shop who sold the car told me that they installed the LN Retrofit bearing. However, after disassembly, it turned out that they used a completely different bearing with the only marking "Made in Germany" and metal *****, not ceramic. The bearing was completely destroyed and it also messed up the intermediate shaft.
Anyway, it's time to make some choices about what to do and not to do at this point. The intermediate shaft needs to be replaced, but I'm pretty sure I don't want a new original-style Porsche IMS bearing in there, so I'm going to have my shop (not the one that did the previous replacement obviously) install the IMS solution.
The question is what to do with the cylinder linings. There is some very light scoring on cylinder 4 and 6, just a single line and you can't feel anything when running your finger nail over it. It's a 3.4 (with around 60k miles) so it's much less vulnerable to bore scoring, so if the IMS bearing had not failed, it probably would have done another 60k miles without any problem.
Another option is to replace the cylinder linings with new Alusil linings. The best option would of course be Nickies, but that requires shipping the block overseas which is quite a hassle.
Opinions please?
I would get the IMS Solution done only if I was sure the rest of the engine doesn�t need any work performed. If it does, you might be better off doing the full rebuild now. For example, let�s say�Doesn�t make sense to drop, call it $8k today (Solution plus other bits) and then have to do the full rebuild only a few years down the line for another $20k.
In summary, an inspection and documentation would be critical. You don�t want some previously failed component piece (such as the failed IMSB) to cause another failure and destroy the engine.
So, this posting is light on details and would benefit from a more detailed description of 'failed'. Did the IMSB disintegrate and cause collateral damage? Are any valves, pistons or conrods damaged? Do you have metal flakes/shavings/pieces in the oil galleries? Are the heads salvageable? You get the picture....
LN is US based and can replace the cylinders with Nickies and have kits to rebuild the engine. But I'd recommend a quality builder to inspect the damage and ascertain what the parts and labor list will look like. And I wouldn't rebuild any M96 engine without contemplating the LN IMSolution (oil-fed plain bearing) to replace the IMSB.
Did they just say it was an LN bearing or was it noted as such on the repair invoice? Seems shady, and a falsified invoice could mean trouble for them. As much of a non-review type person I am, I would make other people aware of their shadiness.
Thanks De Jeeper, but my shop already has a new intermediate shaft ready for installation.
Fortunately it looks like I shut down the engine soon enough -- no damage to valves, pistons, etc. My shop has completely disassembled the engine and there's just the normal wear and tear for a 60k mile engine. I will definitely put in the IMS solution since I don't want to ever worry about this again!
My main decision at this point is whether to also change the cylinder linings, or leave them alone.
The invoice just mentioned "IMS bearing replaced". At that time I was a complete 996 newbie. Only later did I read up and realized that it mattered which type of bearing you put in -- so I asked them which one they used and they said the LN Retrofit bearing. Which wasn't true.
I took a picture but somehow my phone didn't save it. I'll get some pictures.
You need to measure your cylinders for taper and ovality. Ignoring the slight scoring for a moment, with exceseive taper or ovality, even with new rings you wont get good ring seal. If you are doing this right, get the nickies. If you are in europe check with hartech...ln engineering is your go to in the us
I just wanted to make perfectly clear that what was installed was not an LN IMS Retrofit. Many shops will blanket state they are putting in a retrofit bearing and then use a competitor's bearing. Just like everyone uses the name Kleenex when it could be Puffs or generic tissue paper.
We see the same thing with people thinking the DOF is the same as the IMS Solution.
If there is light scoring already, it's not going to get better and will likely get much worse. However like Quadcammer mentioned, if you check the bores they will likely be well beyond the wear limit for ovality and taper (which is just shy of .003"). Re-ringing simply isn't an option.
We have people ship us blocks for Nickies from all around the world, so distance isn't a problem.
The short block program has ended. KS contacted everyone in the industry a few weeks back trying to sell the remaining blocks that the factory did not want.
Are you in a position to have the cylinders re-sleeved without undue financial pain?
have you explored an increase in displacement if you re-sleeve? I went from 3.6 liters to 3.8 liters when my 2003 bearing failed at no additional cost. A nice plus.
my block was sent to LN here in the USA. Not a big deal. I think your decision should be �driven� by how long you plan to keep it.
I have no plans to sell this car. The exterior and interior colors are perfect for me, and the 997 and 991 don't appeal to me as much, so I'm not looking in that direction. There might be a 993 or 964 in my garage at some point, but in addition to the 996. I love how fun it is to drive, combined with some comfort and practicality and that you can drive it in winter, as opposed to earlier cars. I also have a '72 Targa but I still really miss the 996 right now.
I wouldn't want to replace the short block anyway, as I would prefer keeping the matching numbers block.
I do think that keeping the existing bores will probably work for the foreseeable future, but it is a slight risk.
Any opinions on the option to replace the liners with Alusil liners? Are they better than Lokasil or in the same ball park?
I was aware that Kolbenschmidt makes Alusil repair sleeves, however I've never seen anyone actually use them, let alone in an M96 block. It's probably going to cost as much which would then require special pistons (a new set from Porsche) at great cost. This would also limit you to doing the engine to a stock size as well. Not money well spent and it too can suffer from the same scoring issues which we see in 9A1, Cayenne, Panamera, and Macan engines with Alusil blocks.
call hartech in the UK and follow their advice. Endless number of people try to reinvent the wheel on a solution to bore scoring and wear and it just doesn't make sense. Barry at Hartech will clear it up for you and present you with the options available to you at various price points.
The car is back! The engine has been rebuilt using the existing pistons and cylinders -- the amount of scoring after 100,000 km was negligible so I decided to keep these. The rest of the engine also looked to be in good shape, so if the IMS bearing hadn't failed, it would probably have happily done another 100,000 kms. In a way, it's good that it was otherwise healthy, but it also means this rebuild was basically unnecessary. I probably could have left the original dual-row bearing in there and have had no problem whatsoever.
Very bad news was that it was impossible to get hold of the IMS solution -- apparently there is no supply anywhere because there is a shortage of an internal component. Since the intermediate shaft had to be replaced, we just installed the Porsche bearing that was included for now. I fully intend to replace this with the IMS solution as soon as it's available again. No more ball bearings for me if I can help it. For that reason, I saw no advantage of replacing the Porsche bearing with a Retrofit bearing. That new bearing should last at least a year. Does anyone know, by the way, what type of bearing is fitted with a new intermediate shaft from Porsche? Is it the same as the single-row bearing used from 2000? Or is it an improved design?
Here are some pictures of the bearing that failed with the damage it caused to the intermediate shaft. I was lucky -- in a way -- that there was no further damage to the engine.
I'm happy for you she's back on the road!
Did you get a record for the wear of the cylinders regarding taper and ovality or what drove your decision to use cylinders and pistons as they were?
Thanks! The cylinders are almost always out of spec, but they looked good and were certainly no reason for a rebuild, plus I had negligible oil consumption. Had I lived reasonably close to F6I or Hartech as opposed to in another continent/country, I might have contemplated a rebuild there (albeit with a vast price difference). Sending the short block to LN or Hartech also seemed like a major hassle. Finally, my local shop who did the work and who I trust advised me to keep the existing cylinders and they have seen a lot of 996/997s. Anyway I�m happily back on the road.
My shop believes that the replacement bearing had to be installed incorrectly to fail so early, but it is also clearly an inferior one. That I think is the lesson to learn from this.
