Main seal damage from overfilling oil

Maintenance/Repairs
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1

I have heard many people say that overfilling the engine with oil can damage the main seals and lead to leakage. Is this true or just an old wives tale?

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An old wives tale in my opinion IF the crankcase ventilation system is working properly.

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Old Wives Tale

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However…look out for engine RESTORE. I put it in a 93 Toyota 4runner…preheated it with oil pan heater and in still took out the front seal. It was 40 below so add in the variables … but its a word of advice…

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Old Wives Tale

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If it’s really overfull it can do almost impossible stuff. There is some truth to it. Half a quart or an entire quart usually doesn’t cause problems. Five extra quarts can’t be good.

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If the oil is overfilled to the point where the rotating crankshaft comes in contact with oil, the crankshaft will aeriate the oil as it rotates. When oil is aeriated with air the oil pump can no longer pump oil throughout the engine so the engine is starved of oil and the oil pressure falls off.

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No blown seals

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Lmao these guys saying it’s an old wives tale don’t know what they are talking about. It all depends on the oil system as just a half qt to one qt too much and more can raise the oil pressure enough in certain oil systems to wreak seals I’ve seen it over and over again. I’m a diesel mechanic and build hot rods and motorcycles on the side. Short answer no it’s not a wives tale and yes it can wreak your oils seals take it from an expert who has seen it time and time again!!!

10

I guess you mean ’ wreck ’ seals .

11

Come on. The level of the motor oil in the engine has zero, zilch, nada to do with the oil pressure. The pressure stays the same as long as the oil pump pickup tube is submerged. Oil pressure has no effect on main seals although an overfilled engine can certainly leak oil past a main seal; and especially if there’s a PCV problem.

Funny thing is when I was about 17-18 years old and in high school (more than a few decades ago) I believed the same cxxp when I worked part time in a gas station. With age comes knowledge; at least in some cases.
And the old wives tale continues 9.5 years later.

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