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Engine blow-by

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Old Aug 16, 2020 | 12:25 PM
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Engine blow-by

I have some blow-by on my engine. I am currently using Shell Rotella 15-40 and 1 qt of Lucas oil stabilizer. Any suggestions what would help with this problem other than a rebuild? How about Castrol straight 40 wt and more Lucas. I am just trying to reduce the amount.
Thanks
 
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Old Aug 16, 2020 | 12:55 PM
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Since most blowby circulates through the CDR valve then into the intake stream you have no idea how much blowby you have unless you first block off the CDR valve so all blowby is trapped in the crankase. Then to do it right, a reading is taken with a manometer plumbed into the oil fill tube. If the reading exceeds 6" at 3000 RPM blowby is excessive. Can't see how switching oil would have any effect, engine wear is engine wear regardless of choice of oil.
 
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Old Aug 16, 2020 | 02:55 PM
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Originally Posted by RaymondIV
Since most blowby circulates through the CDR valve then into the intake stream you have no idea how much blowby you have unless you first block off the CDR valve so all blowby is trapped in the crankase. Then to do it right, a reading is taken with a manometer plumbed into the oil fill tube. If the reading exceeds 6" at 3000 RPM blowby is excessive. Can't see how switching oil would have any effect, engine wear is engine wear regardless of choice of oil.
I figured the higher viscosity might make the compression rings "seat " better in the cylinder.
 
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Old Aug 17, 2020 | 09:06 AM
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Originally Posted by Tom D
I figured the higher viscosity might make the compression rings "seat " better in the cylinder.
I thought I read a while back on this forum that the IDI is known for having quite a bit of blow by and it's not much to worry about?

As far as oil, I've switched my rig to the full synthetic Rotella 15/40w and it seems a bit happier chewing on that. Gained a hair more oil pressure on the factory gauge. Once I recover a bit from all the money I've thrown at my rig I'll put in some after market gauges and report back with accurate readings. Suppose I should track down my slow leaks first...
 
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Old Aug 17, 2020 | 10:53 AM
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6" of water is only 0.2 PSI
 
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Old Aug 17, 2020 | 11:02 AM
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You're big on manuals, look it up. I've tested quite a few DT466's and their factory spec is exactly the same----6" at max no load RPM.
 
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Old Aug 18, 2020 | 09:02 AM
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Thank you all for your input. I will try to borrow a manometer and check it out. It doesn't seem to be any different than 100k miles ago. I guess I shouldn't worry about it. I certainly am not going to rebuild it.
 
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Old Aug 18, 2020 | 10:10 AM
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I use a Magnehelic gauge myself, with a pair of adapters for the screw on oil filler cap/

There are several DIY blow by testers online that are easy to construct/

Anyway you won't know what it is until it is measured.



 
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Old Aug 18, 2020 | 10:20 AM
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Even when new the IDI had a lot of blowby, it's a design of the rings.
 
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Old Aug 18, 2020 | 12:56 PM
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All engines have Blow By to some degree. It is a natural process of combustion
with in the engine. Some pressure will leak past the rings. The oil in the crank
case gets hot,some oil mist and blow by get sucked into the intake and burned.
Big deal.
Seems no matter what car/truck forum, every one is stressed out by Blow BY.
Want a catch can of some sorts, because the stuff will ruin their engines.

On one Mercedes Forum there is a long winded discussion on Blow BY. The
title as I remember is something like, Catch a bag of Blow BY.
They attached a black Garbage bag to see how long it took to fill. Was a funny
thread.


Charlie
 
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Old Aug 19, 2020 | 10:08 AM
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True, true, and true, Charmalu! But you forgot about the often verbally abused CDR valve. It's accused of causing everything but flat tires.
 
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