Autopsy of a "good" IMS bearing

[jdlmodelt]

So drive it regularly, get the RPM's up. pay attention to sounds, keep the oil changed with the right kind of oil, and enjoy the ride? Mine's a 2.5l

[Walter White]

Originally Posted by Jamesp

Cutting apart the bearing to inspect the inner races revealed a series of equally spaced scuffed lines running across the bearing race. These appeared to be discrete areas of fine pitting on the races. There were 8 lines on the inner race, and 7 lines on the outer race. This is the inner race:

I am speculating that it may be a shock that is sent through the cage when the balls change from being loaded to unloaded. A ball that is under load pushes the cage, and the balls that are not under load are pushed by the cage. Perhaps a shock is sent through the cage each time a ball transitions from loaded to unloaded. This causes the ball to slam from one side of its cell to the other side of the cell. Maybe this creates a shock that travels through the whole cage and affects all the balls at once. Maybe this shock causes the balls to skid for an instant as the cell wall crashes into its ball.

[Jake Raby]

Looking at new, good used and failing bearing surfaces (races and balls) under an electron microscope really tells the story.

These photos are published in my book :-)

[Walter White]

Here is some information I found. Information on this site seems easier to find than most.

Knowledge of Bearings

[edc]

Rather than start a new thread here is some text and photos of my old IMS from a 105k miles 2004 car.

http://www.boxa.net/forum/index.php?showtopic=59044&page=3#entry709368

[edc]

Just took the seals off my bearing. It looks quite different to the first post.

[Jamesp]

Originally Posted by edc

Rather than start a new thread here is some text and photos of my old IMS from a 105k miles 2004 car.

http://www.boxa.net/forum/index.php?showtopic=59044&page=3#entry709368

Your link does not work.

[pothole]

Originally Posted by Jamesp

Your link does not work.

It does, you just have to be logged in as a member to see it. God knows why they want to restrict traffic like that, but they do.

[Jamesp]

Originally Posted by pothole

It does, you just have to be logged in as a member to see it. God knows why they want to restrict traffic like that, but they do.

Hmm.... Sure would be convenient if it were posted here...

[edc]

Here's a cut and past of the relevant posts:

Well, I now have the old IMS bearing. First things first, I am no engineer despite working for an aerospace engineering company! My photos and commentary are merely observations.

For context, and repeated from earlier posts, the car is a 2004 986S with 105k miles. No paperwork but confirmed decent history from OPC with regular servicing. I don't know for sure but I believe the car was a daily commuter although the condition of the interior suggests a car with half the miles and a weekender. I believe the oil changes were all done with 0w40 Mobil 1 (oil change prior to sale was and this spec oil is what OPC use).

The original NSK bearing was replaced with an LN ceramic one as part of a schedule of works including a clutch change.

Russ commented that this was one of the most solid bearings seen. Holding the threaded shaft and wiggling the bearing shows no play at all. Holding the shaft and attempting to spin the bearing by finger then next to noting happens. You have to maintain contact with the bearing outer race and rotate it rather than spin it. Whewn turning it there is no notchiness, the movement is very consistent and smooth. There are no weired noises.

The seals seem completely intact, no pitting or any sign of damage. There is a small indentation on one part of the seal pictured below but I presume this was done at removal or in transit via post. The outer race has some light markings that go round the circumference. Running your nail over them you cannot feel them.

Old bearing:


Marking around circumference:






Indentation on seal:




When I get the chance I will remove the seals and have a look inside.

Here is the next IMS instalment. The seals are now removed. Again, take what I say with a pinch of salt. I don't see many bearings in different states of ab/use.

To remove the seals was reasonably straight forward. The smallest flat blade bit pierces the seal. Trying to lever it out on the outer edge proved pretty hopeless.

Here is one side of the bearing opened up.

Nothing much untoward here:







Back of the seal was pretty clean, no real evidence of any debris:




In this shot I wiped my finger over some of the ball bearings. You can see at the 3pm position the bearing is cleaned of grease/oil and is silver. The bearings are otherwise covered in a light film of grease/oil which has a silver (probably metal) tinge to it.




This shot shows the seals and various finger wipe marks to show the colour of the oil/grease inside the bearing. It seems evident that oil has got past the seal but is generally a golden brown colour and the same sort of colour as a good clean oil. The grey smears are what has come off the face of the ball bearings:

[edc]

Here is a shot of the other side of the bearing. You can see at the 4pm position again the finger wiped ball bearing. Look at the grey film grease suspension that has been removed:





Next step would be to remove the ball bearings to look at the race. However, I am all out of tools for that aside from brute force.

FYI my now not so clean white board was a polystyrene bit of pizza packaging

[Jamesp]

Looks like there was no grease in the bearing, just oil. This looks similar to the Pelican Parts replacement kit. What are the numbers on the bearing's grease shield?

[edc]

I'll have a look later to check for any part numbers. This isn't a pelican part as far as I know. It was taken out of my standard engine.

[Jamesp]

I have to retract my last post - The pelican parts is a single row bearing and this is a double. I was looking at the bolt and it looks beefier than the stock bolt out of my single row.

[edc]

Mine is a 2004 car so a single row ...

[edc]

Poland nsk 917 6204du17