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LN Engineering Ceramic IMS Bearing Failure at 30k miles
I had a local shop preemptively replace original IMS bearing with the LNE ceramic bearing in August 2013 at 54 kmi. They said that they had to do an inspection in which they cut open the oil filter and it was clean.
The magnetic drain plug was clean (just microscopic fuzz) at each oil change until I changed the oil in January 2015 at 86 kmi, when there were lots of metal flakes up to about 0.8 mm long. I cut open the oil filter and saw the same thing. I drove a few hundred more miles and the drain plug had more flakes on it.
Here are some of the flakes that I wiped off of my magnetic drain plug with a paper towel.
The car ran fine and made no unusual noises. After getting conflicting advice from several mechanics, I stopped driving the car, had the motor removed, and sent it to MB Motorsports in Illinois for a rebuild. They disassembled it and found that the IMSB was wobbly (see video at https://docs.google.com/file/d/0Bwcd...lnUGJURkk/edit).
As you can see jn the photos below, the ceramic ***** are fine, but the inner and outer races have a lot of steel missing. This steel from the IMS bearing had gotten to the crankshaft and damaged its bearings. Apparently I caught it a while before complete engine failure, which would have cost more for the rebuilt as my core would have been almost worthless.
Here's the bearing still in my old engine. The video shows how the shaft protruding out is wobbly.
The IMS flange. On new bearings, the date code (G2 here) should match that on the shoulder bolt (H2 below). Mine from two years ago obviously don't.
The dot-peened label from LNE on the shoulder bolt.
After removal, the ball bearings and races are still held together.
Disassembling the bearing.
With the rubber removed, the ceramic ***** are visible.
Disassembled.
Nasty wear on the outer race.
Ugly wear on the inner race. This appears to be the source of my metal flakes.
The LNE IMSB cost about $3K to install. The rebuilt engine and installation is another $14K or so. I'm out $17K, when if I had done nothing, I would probably have been fine (statistically, I've read of an 8% failure rate for the 996.2s, and those are lightly driven, which is not my case).
When I had the LNE IMSB installed two years ago, I thought it was a permanent, low-risk fix. I am particularly disappointed that at some point after that, LNE decided that this product, the IMS Retrofit, was not a permanent fix. They now say that if you love your car (which I really do) to install a different product, the IMS Solution.
I called LN Engineering and they didn't have anything helpful to say. The technical guy I talked to said that the single-row bearing was a weak design (agreed) and that if it was going to go, it would have in the few thousand mile (no, it was fine for about 30 kmi). They did not record my name or any other information, so they are not taking statistics on this.
Here are the four replacements for the stock IMSB I know of:
* LNE IMS Retrofit, which has ceramic ball bearings. This was an interesting idea, but it turned out to be a bad one, because the harder ceramic bearings can wear the steel races. Heck, I use ceramics to sharpen my very hard steel knives.
* Pressure-fed steel or ceramic ball bearings, which Pedro's Garage uses. This resolves the problem of lack of lubrication that the stock bearings had. I would be wary of the ceramic bearings.
* LNE IMS Solution, which uses a pressure-fed plain bearing. This is a great idea, and it's not a new one: Porsche used in on intermediate shafts for 911s up through the 996s with the M96 engine. The 996 GT3 still used it. The biggest problem I have seen with this is finding a local installer.
* German roller bearings, which MB Motorsports, Vertex, and other rebuilders use. Roller bearings can handle much higher loads than ball bearings because the force is distributed over a much larger area, resulting in a lower contact stress. I've heard it said that roller bearings are not good for side loads. I don't see an issue in this case because the other end of the intermediate shaft already has a plain bearing holding it in place. I've also heard that roller bearings cannot handle the engine speed. Take a look at a parts diagram for the transmission. It has roller bearings, and the input shaft is of course running at the same speed as the crankshaft. And the IMS runs at 2/3 of the crankshaft speed.
** One more product I have to comment on is the LNE IMS Guardian. This is a pair of electrical contacts integrated into their magnetic drain plug. When enough metal flakes pile up, the contacts are shorted together, closing an electrical circuit. This just tells you that your engine is generating ferromagnetic metal flakes, most likely from the IMSB. The problem is that by then it's too late to replace the IMSB. LNE's own rules require that there be no metal flakes in the oil before installing the IMS Retrofit or IMS Solution. This means that the owner is already screwed and needs an engine rebuild. The car can be driven a while longer before complete engine failure, or the driver can stop (like I did) before the engine dies at an inconvenient time and get a rebuild. This same concept is used in some aircraft internal-combustion engines, and it's clearly a good idea to land once there's metal in that engine oil. I just don't see it helping much in a car as long as a magnetic drain plug is used and inspected at each oil change.
While figuring out what to do, I'd like to thank Jake Raby for his many e-mail responses to my questions. As a PhD engineer, I really respect and appreciate what he and LNE are doing: finding the M96/M97 failure modes and addressing them (which really was Porsche's job, but they dropped the ball on that one). In the end, shipping my car to Flat 6 for a few months or more (depending on their lead time) and spending $22K+ just wasn't possible for me right now, although I do believe that the result would be nearly bullet-proof. And I could have gone from 3.6 to 3.8 liters with new LNE Nickies cylinders for the same price.
In the end, I found an X51 engine that was being rebuilt at MB Motorsports for $12K that I could get in a month or so (plus $2K local installation). I'd like to thank Agnes and Martin there for taking photos of my engine and the used bearing. I know Jake and MB are feuding, but both know what they are doing and offer great products at different price points and with different lead times.
I don't understand the H2 v. G2 date stamps and what that implies?
I also don't understand the rubber seals since I thought the retrofit was splash lubricated. . . in the pictures on the LNE website it looks like the retrofit bearings don't have these seals. Was this a change in production, or just not in the photos on the LNE website?
I don't understand the H2 v. G2 date stamps and what that implies?
I also don't understand the rubber seals since I thought the retrofit was splash lubricated. . . in the pictures on the LNE website it looks like the retrofit bearings don't have these seals. Was this a change in production, or just not in the photos on the LNE website?
The number and letter designations are production run dates and batch identifications.
All the LN bearings are if an open design, the seal is ONLY on the backside of the bearing to keep oil from filling the IMS tube with oil.
I have noted the localized inner race wear that's seen here with many OEM bearings that were failing. I have finally found what leads to this, and it will forever change the qualification process for engines that will be retrofitted in the near future.
The number and letter designations are production run dates and batch identifications.
All the LN bearings are if an open design, the seal is ONLY on the backside of the bearing to keep oil from filling the IMS tube with oil.
I have noted the localized inner race wear that's seen here with many OEM bearings that were failing. I have finally found what leads to this, and it will forever change the qualification process for engines that will be retrofitted in the near future.
In the first photo, the black seal is on the front side though. Um...
"I was rear-ended last year hard enough to knock the aftermarket stereo out of the dashboard. The external damage looked minor (see photos). It turned out that the internal "rails" that act as a frame were crushed inward an inch on the right and half an inch on the left. You can see that the right tailpipe extends more than the right one and that the rear panel has buckled a bit. It cost $12K to repair, which included removing and reinstalling the engine.
About 30k miles ago I had the LN Engineering IMS bearing installed. I only use Mobil 1 0W-40 and change the oil and filter at 2/3 the interval that Porsche recommends. At each oil change there has just been a little fuzz on the magnetic drain plug. I just changed my oil last weekend for the first time since getting hit. This time my drain plug was completely coated with flakes of metal in the 0.4 to 0.8 mm size range. I cut open my filter and saw more of the same.
Usually metal in a 996 engine is from the IMS bearing failing, but mine is now ceramic, so that shouldn't be it. Does anyone know how an accident might cause the metal flakes in the engine oil? Is there something like an engine dimension that I can measure to show that the accident caused engine damage. If it's from the accident, of course I'll have the other driver's insurance pay for it. I don't see coming up with $22K to have the engine rebuilt any time soon. "
In the first photo, the black seal is on the front side though. Um...
That looks like a cage to me, it doesn't extend out onto the seal groove in the outer race or inner race. The seal on the back side is marked RS1 which is the designation for single sided sealing.
04-19-2015, 11:44 PM
LN Engineering Ceramic IMS Bearing Failure at 30k miles
