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How to cut open an engine oil filter and what to look for.

Oil Filter Analysis

When a machine overturns while it is running, oil stops circulating very quickly due to the loss of oil pressure. The oil filter becomes a time capsule. Remove the filter from the engine and cut it open. It will reveal the condition of the engine immediately prior to the catastrophe that ensued. Sample the oil inside the filter for lab analysis.

filter element after a major bearing failure

Someone with sinister intent might change the oil to make the damage match their story, but they hardly ever think to change the filter. Someone with sinister intent that is mechanically savvy might change both, but he can't use new oil because he has to make it look used. Sample the oil inside the filter and take a second sample from the sump. See if the results match!

Chicken or Egg?

An engine will normally be disassembled for one of two reasons: when an engine has high hours or miles or when an engine has experienced a failure. When an engine owner experiences a failure, he might make a claim regardless of whether it has been established that a loss occurred. Insurance claims for mechanical damage to engines fall into three major categories: introduction of a contaminant by alleged vandalism, sudden volumetric loss of oil by alleged vandalism, and overturn by physical rollover of the vehicle during operation. The oil filter analysis I discussed above is an important component of failure analysis for all categories, and it is the easiest to accomplish because no engine disassembly is required. Often we need to determine which came first, the failure, or the "loss"?

The most probable causes of major engine failure are overheating, lubrication (lack of or contamination of), abrasive grit, detonation, and mis-assembly. We have worked claims on every category where we were able to prove the claim meritless through failure analysis that showed that the real source of damage was not a covered loss. In the majority of these claims, lack of lubrication or contaminated lubricant is the cause of damage.

Lack of lubrication damage refers to an insufficient film of oil between the crankshaft journal and bearing. Lack of lubrication can be caused by low oil level, wrong oil viscosity and other conditions that degrade engine oil such as the presence of water or anti-freeze, or oil contamination. Examine the bearings and crankshaft for indications of an irregular wear pattern. Polishing of a bearing occurs when the oil film between the bearing and crankshaft journal decreases for an instant. This is a normal condition that can occur during starts, high oil temperatures or extreme loading. Usually, bearing polishing is not serious because the oil film is restored after a very short period of time. Bearings damaged from debris will have either scratches or embedded debris, and in serious cases, can look like a lack of lubrication failure.

The first stage of lack of lubrication failure for a bearing is smearing. A smeared bearing will have some displacement of the lead-tin overlay, usually at the center of the bearing. A smeared bearing progresses very quickly to a scuffed bearing if the oil film is not restored. A scuffed bearing shows additional displacement of material, caused by extreme heat. A seized bearing is the final stage in the progression of damage caused by insufficient oil film.

Familiarize yourself with these images and know what you are looking at when it comes to bearing appearance. Don't buy repairs for engines that suffered a mechanical failure that is not a covered loss, or worse, where no damage occurred. The two images below are normal bearings:


Below is a link to a video of me cutting an oil filter open for analysis.

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