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Old 08-19-2014, 05:23 PM   #1
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Crankcase pressure results - is 5.8 bad?

I've been under the impression my AOS needed to be replaced. I'm burning through about 3 quarts of Mobile1 over each 5000 mile oil change interval. My AOS is 16,000 miles old and there is a slight amount of liquid oil in the tubes between the AOS in the intake. However this evening I connected a pressure gauge to my oil tube and am only pulling 5.6 - 5.8 inches at idle. I hear 5 inches is normal.

Is 5.8 inches reflective of a bad AOS?
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Old 08-20-2014, 02:32 AM   #2
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I've been under the impression my AOS needed to be replaced. I'm burning through about 3 quarts of Mobile1 over each 5000 mile oil change interval. My AOS is 16,000 miles old and there is a slight amount of liquid oil in the tubes between the AOS in the intake. However this evening I connected a pressure gauge to my oil tube and am only pulling 5.6 - 5.8 inches at idle. I hear 5 inches is normal.

Is 5.8 inches reflective of a bad AOS?
Depends upon inches of what. You should be around five inches of water, while most vacuum gauges are in inches of mercury, where 1 inch of water equals 0.0735 inches of mercury. So if your gauge is in inches of water, you are fine; however if it is in inches of mercury, you are in trouble.
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Old 08-20-2014, 06:28 AM   #3
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Yes inches of water.
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Old 08-21-2014, 07:09 AM   #4
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Any thoughts to why my AOS is passing oil but pressure readings are normal? Should I replace it or not?
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Old 08-21-2014, 07:44 AM   #5
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how many miles on motor?
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Old 08-21-2014, 08:30 AM   #6
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Any thoughts to why my AOS is passing oil but pressure readings are normal? Should I replace it or not?
The AOS will pass oil well before it totally craps out. Yes, I would replace it,
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Old 08-21-2014, 09:26 AM   #7
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how many miles on motor?
About 62,000.
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