Byprodriver

Did you find the IMS tensioner paddle in place like in your photo? That wear button pad looks very thin.

Ahsai

Yes and that's the amazing part. The tensioner held it in place and it's ground by the IMS chain so it became so thin. If it had fallen off, it probably would have taken the timing chains with it.

Engine was still running. No valve or piston damages. The LN ceramic ***** are so tough that they still held the IMS more or less in place while the inner race was ground down gradually.

Imo000

All ceramic bearing ***** are tough, not just the ones used in the LN bearing.

Ahsai

I finally split the case and found the rod bearings, the main bearings, and the crankshaft are all in GREAT shape and I found no other collateral damage. Can't imagine they have 100k miles on them!

I think I can conclude IMHO that indeed the IMSB failed and it took out the following parts with it:

- IMS
- Bank 1 scavenge pump
- Main oil pump
- IMS tensioner paddle
- IMS timing chain
- Slight and fine scratches on both the pistons and the cylinder walls. More on cylinders #3 and #6, the ones closest to the IMSB. I believe the scratches are from some finer metal debris. Probably could have been avoided if Cringely had stopped driving the engine in time.

I can also conclude the following:
- the oil filter valve was NOT bypassed so no metal debris have passed the oil filter. Only the fine metal dust suspended in the oil that can't be removed by the filter remains in the oil (That's why the bearings are still fine).
- the high aluminum content in the oil was from the ground up IMS paddle (by the steel IMS timing chain, and not shed from the cylinders).
- ceramic ***** are one tough son of a bitch. In case of failure, they may still hold the IMS in place and give you enough warning to stop the engine.
- when the IMSB fails, the heavier and bigger debris are settled at the bottom of the IMS and will not reach the oil pan. Only the small and medium size pieces made it to the oil pan. All debris got flung around and most of the damages are in the flywheel end of the engine.

alpine003

So just to recap, PO had LN bearing put in. Any signs of faulty installation? I forgot if PO had LN retrofit put in after he started to have any issues or not(noise or otherwise). Also were you able to closely examine the IMS bearing itself(particularly the race and cage themselves)?

Paul Waterloo

Thanks for the update and great information.

Ahsai

No sign of faulty installation I can tell plus it lasted 25k miles so probably it's not due to a botched installation. The PO (Cringely) put in the LN retrofit when he bought the car as a preventive maintenance. No issues were present at the time except it was mentioned there's a slight rattle noise from the engine that couldn't be traced. The rattle also went away after the retrofit. However, no qualifying inspection was done (inspect filter, drop oil pan, etc.) before the retrofit. The first oil change after the retrofit they found some metal pieces so a magnetic drain plug was fit. Then the next oil change they found no metal, then later on the engine failed.

The IMSB autopsy was in post #182 with photos.

Flat6 Innovations

Its hard to say what happened first without having the parts to review extensively.

That said, the engine appears to have had the cylinder scoring first, before the IMSB issue. this is why the scoring is more evident only on the one bank. if the IMSB led to the cylinder scoring, the damage would have been engine wide, not just on the most problematic bank of the engine. I also say this because the wear is concentrated at the mid- bore portion of the cylinder, not all the way up and down the bore. This is classic for the engine in question, due to rod angle and side loading at mid bore being highest due to the rod/ stroke ratio and pin height.

Cylinder wear debris is very damaging to the IMSB and other items within the engine, as it is super light and easily is suspended in the oil, being delivered everywhere internally. Cylinder wear debris is also harmful, as it is very high silicon content aluminum. This also explains more about the UOA results.

Failure assessment is forensic mechanic- ology and is difficult, to say the least.

Ahsai

Hi Jake, thanks for chiming in. Actually the piston and cylinder scratches (very light and fine at mid-bore) are on all 6 cylinders, not only limited to one bank. They are definitely worse on #3 and #6, on the IMSB side so that's why I thought the scoring is due to the IMSB debris.

Flat6 Innovations

Look at the case closely. You'll see that the IMSB is somewhat partitioned internally, which keeps the IMSB wear debris away from other internals being favored.
remember, ALL the splash oil from this engine is delivered by the piston squirters and rod bearings as waste oil, and is fed there by the main bearings. The crank scraper keeps sump oil way down in the sump, and away from the cylinders, as splash oil.

The oil that is fed from both these sources first passes through the filter/ housing.

Think about those things for a while.

Ahsai

Just to clarify, the scratches on all the cylinder walls and pistons are very very light (far from catching finger nails). The photos make them look much worse than in real-life.

Flat6 Innovations

That means nothing to me. :-)

Ahsai

Yes, Jake, I also noticed that design while examining the IMS, the black plastic oil baffle below it with gaskets, and the residual debris. So are you saying the the oil that passes the squirters (same oil that goes to the crank bearings) is already filtered so there wouldn't be any larger debris that could cause scoring on the cylinders and pistons? In other words, any scoring CANNOT be due to oil laden with fine metal debris?

Flat6 Innovations

Never say never, BUT the oil doesn't splash there. It is delivered there.

I bet the oil that was material laden bypasses the filter due to the stupidest oil filter housing design in the world. Heat the oil filter housing to 220* and see how much spring tension you can measure on the bypass spring.

These are getting old and causing all sorts of issues, but no one listens. I quit caring a long time ago.

cringely

I guess that this is the first example of performing preventative maintainence and having it bite you on the backside. I really thought I was being smart in replacing the IMS.