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Old 09-09-2018, 06:49 PM   #1
Bahaa425
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Default Too much blow by?

Hello if you could help me diagnose whether or not Iím getting some excessive blow by, that would be great. Below is a video of my oil filler cap with a small amount of vapor coming out once the engine is off. When the engine is idling or being revved, I donít have any vapor, only once I shut the engine off.

Motor has about 3500 on the rebuild.

Video url: https://youtu.be/FQoK1R4kPUw

Let me know your thoughts
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Old 09-09-2018, 08:03 PM   #2
Bahaa425
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Correct me if Iím wrong, but after reading some more I found that this is normal in most cases. As explained on another forum


ďCondensation develops in the crank case from the engine heat cycling hot & cold as it draws in humidity from the air.
Some of those vapors coming out of the oil fill is moisture boiling out of the oil and this is very normal. All moisture would be gone after 30 minutes or so of driving after fully warm. Oil has a flash point of 350F to 450F degrees depending on the oil. The flash point is the temperature that contents of the oil turn from liquid to vapor.
Even though the oil temp normally is about 20 to 40 degrees above the coolant temp about 240F, the oil is always in contact with internal parts that normally reach well above the flash point of the oil.
The exhaust valve guide area, upper piston area are those hotspots that will burn tiny amounts of oil at all times turning to carbon & releasing vapor as oil and the additives in it burn off into the crankcase.
Most the vapors are sucked up & re-burned via the PCV system but the PCV has limited function at idle.
This explains other normal crankcase vapors & why oil gets dark & old. Ē
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Old 09-09-2018, 08:13 PM   #3
viper_crazy
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That looks pretty normal to me. I wouldn't worry about it, as long as you don't have "mayonnaise" in your oil, you're good.
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Old 09-09-2018, 09:00 PM   #4
Bahaa425
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Quote:
Originally Posted by viper_crazy View Post
That looks pretty normal to me. I wouldn't worry about it, as long as you don't have "mayonnaise" in your oil, you're good.
Yea oil is clean, just been seeing some high feedback correction numbers under low load ~1.2 and under 3k rpm and just trying to rule out some things. I believe itís just noise but never hurts to be cautious
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Old 09-09-2018, 09:16 PM   #5
viper_crazy
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When was the last time the plugs were changed?
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Old 09-09-2018, 10:24 PM   #6
Bahaa425
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Quote:
Originally Posted by viper_crazy View Post
When was the last time the plugs were changed?
During the rebuild so ~3500 miles ago.
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Old 09-13-2018, 10:54 PM   #7
mrbunz
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Mine does the same.. i dont think you need to worry.
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Old 09-14-2018, 12:10 AM   #8
viper_crazy
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Probably just noise. If you rebuilt with forged internals, you may need to desensitize the knock threshold a bit. If you can't do this, you'll need a protune. If you went with an OEM block, then there's not much you need to do, as long as your DAM is at 1.0 (or 16, depending what year you have), I don't think there's anything to worry about.

Keep in mind, the ECU is constantly trying to push the limits of the spark advance within its maximum allowed parameters. When it detects a bit of knock, it backs off a bit to a safe level and advances a bit more a again, and the cycle repeats. As long as you don't have any permanent knock correction (or your DAM drops from its maximum value), the best you can do is just monitor/log from time to time as a bit of a health check up.
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Old 09-14-2018, 03:34 PM   #9
subaru_gc8
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if youre engine is running and there is a good amount of smoke coming out of the filler tube, then you have a problem. what you are testing means nothing
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Old 09-14-2018, 03:57 PM   #10
cn07
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^^^^Word
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