crater in rod bearing, what does this mean? Options

[mightyohm]

This is an extreme closup of a rod bearing on a 2.0 I tore down. There is a small crater in the bearing. It is at least a few thousands deep and definitely catches a nail. The scratches through it are from me scraping at it with my nail to see if more would flake off.

Anyone seen this before? I have a cam bearing that is much worse but no pics yet.

[mightyohm]

Another pic, different angle.

Nevermind all the crud on that bearing, it's been sitting outside for a while now. It was clean when I removed it.

[ChrisReale]

Oil starvation? (IMG:style_emoticons/default/confused24.gif)

[mightyohm]

Here's the cam bearing, much worse.

[ArtechnikA]

i donno - i don't see as many engine parts as the experts. that kind of thing looks like corrosion, tho.

"what does it mean"? it means you need new bearings ! but you knew that. i'm pretty much of the opinion that rod bearings should be replaced any time the heads are off, 'cause they have a hard life in our engines, they're not expensive, and they're not that hard to replace.

just remember the scene from 'Men In Black,' where there's "always an Orgelian Nebula, or a Wooznatchian Galaxy" or some such damned thing, and the only thing that lets people get through their ordinary lives is that They Do Not Know.

i bet if a bunch of us went out and tore down our engines we'd find any number of lurking horrors, especially those of us with older cars with incomplete history. the only thing that gives ne strength to turn the key every time start it is that it ran okay the last time i did, and if there are lurking horrors, I Do Not Know.

when i have a Darned Good Reason to tear it down, i will Know - but until that time, i'm going to drive it as if a minor bearing irregularity is no cause for alarm 1) because i have no choice and 2) because that's close enough to the truth for me.

[Mark Henry]

Delamination, seen it many times.
The bearing has seen a long hard life, good job you're replacing them.
Main cuprit's are age, overheating and oil breakdown.
I have a customers crank with the center main like that, will need a .020 cut just to clean up. We found him a better crank.

[Jake Raby]

The OEM bearings sometimes had this problem. I see ALOT of cam bearings that have that issue...

[Mark Henry]

Yep, OEM main bearings.

[mightyohm]

Jake, you are right, these are OEM bearings with VW part #s on the back. I don't think this motor has ever been opened up before. Good to know guys... Thanks for the info. At first I thought maybe I had done the damage during the disassembly process but once I saw the rod bearing I knew for sure it was not something I could have done.

[Jake Raby]

A tad bit of the delamination won't hurt anything for a long time... It just holds some extra oil .

The New mahle bearings also do this in a short time- so do Metal Leve... I Like Glyco rod bearings and KS mains....

[Matt Romanowski]

I was always under the impression, especially with old motors, that this was a sort of "acid etch." I have only ever seen it in old motors.

Matt

[tracks914]

I've never seen it but what I would like to know is, if it is delamination, where did the babbit go? If it came off, peeled off or whatever, it would surely "pick up" and wipe (or score) the rest of the bearing.
I deal with babbit bearings for a living working on large and small hydro electric generators. We scape them, repore them, fix them, melt them down whatever it takes to get them running again but have never seen "holes" like that without a "wipe" next to it. (IMG:style_emoticons/default/confused24.gif)
I kind of like the"acid etch" theory but haven't seen one first hand to offer credible assistance.

[Thorshammer]

Many of you have seen this before, but this is indeed corrosion. When the motor is stored for a long period of time, the oil should be changed prior to storage. Combustion contaminates when mixed with moisture can form acid concentrations. The surface (babbitt) of most bearings is very porous and is easily attacked or etched. The first time the motor turns over, it flakes off and this is what you get. Some aftermarket bearings don't use as porous a material as the factory bearings and it will happen much less. But keep in mind when you rebuild a 914 motor you don't normally plan on storing it for long periods of time. The bearing porosity is also a good reason to "presoak" rod and main bearings in oil warmed to about 140 degrees and then allow them to cool. This does a much better job of bearing break in than assembly lube alone. Others may have a better way. Suggestions?.


Erik Madsen
Madsen Engineering