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Bearing material

Practical Engine Building

Relevant Module: Failure Analysis > Dirt & Debris Related Failures

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Can bearing material from a worn engine bypass the oil filter and re enter the engine ? Or is it to large to bypass the filter element .

In theory, no - but in practice maybe. Spin-on oil filters have a bypass valve built into them, and if the filter has enough debris built up on it to restrict the flow, the bypass may open and allow debris to pass into the oil-ways.

If it's a worn engine, regular oil and filter changes should have meant that there's only a very small amount each time, and the bypass should stay closed. There is another exception, though - if the oil is viscous enough, usually on a VERY cold start, it's possible for the bypass to open because there's so much resistance to the thick oil from the filter element.

If you're enquiring because you ran a bearing, you may very well get away with pulling the oil pump, thoroughly cleaning it AND the pickup filter and pipework, and the engine oil passages btween the pump and the filter mount, but the best option is to pull the engine and thoroughly clean all the passages out. If you have an oil cooler, etc, that will also need to be cleaned.

There have been engines built that didn't have any oil filters, relying on a simple mesh screen on the pickup, and the first gen' Chev' small block rear main bearing was fed unfiltered oil because of the way the pump was retro' fitted - the first year's engine didn't have one and it was added later. Don't know if the big block had the same issue, as haven't had one apart, but I doubt it.

Like Gord said, theoretically it shouldn't happen, but in practice it can, and I agree on cold start you may bypass a significant amount.

There are a number of places bearing material can come from and cause damage. Engine bearings, turbo bearings, oil coolers, cam phasers and VVT gears to name a few. I'm not clear what situation you're describing, but in case it helps....after an engine issue occurs, I replace all those parts to avoid contamination after damage repair.

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