Cat D2 D3400 Main Bearing Babbitt Separation - What Causes This?

Hi Toby,
my guess from the pic attached and Cat literature with similar pictures of spalled bearing surfaces is Cat say from :- exceeding the expected life of the bearing.

By the wear pattern low on the bearing shell I could suspect excessive clearance from undersize journal or as said above just plain fatigue of the bearing material over many hours of operation.
Lugging by operating in too high a gear when towing etc. may play a part too.

Maybe do some clearance checks and see what you find. Also suggest check the crank for truth, ie. bend, twist, etc.

Google could come up with many pix and other scenarios too.

Interested to see what you can come up with.

Cheers,
Eddie B.

I know I must be dreaming but it looks like a hammer blow near your thumb. Metal has been displaced to the side.

In the IH world the big v8’s can wipe out cam bearings if sitting for a long time. The recommendation there is to prime the oil system before turning the engine so you don’t wipe out the babbit layer. Were there any chips of babbit in your oil pan?

That looks to me like typical erosion caused by water in the oil.

It looks like electrolysis removed some component or impurity of the babbett. Maybe there was some slag that got into the pour.

Welding on the machine. Not properly grounding close to your weld area will arc bearings.

I had the same thing in my D4-2T:
[attachment=55749]2013-07-13 024.jpg[/attachment][attachment=55750]2013-07-13 026.jpg[/attachment]
There were rust pits through the bottom of the water jacket where anti-freeze was seeping into the oil but it wasn't enough to notice. There was enough sediment in the bottom of the water jacket to keep the holes plugged somewhat, but after cleaning it out, this is what was left:
[attachment=55751]2013-07-13 028.jpg[/attachment]
After finding this, I assumed that the bearings were dissolved by anti-freeze.
Brian

Yes, seen it before. Worst case I've seen was Jack up in Hood River Oregon (if I recall right) when he was going through the building of his D311 bio-diesel generating plant. Looked like worms had eaten the bearings. Product of water in the lube oil and acid formation that eats the bearing material.