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Old 19-07-2018, 15:04   #1
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Checking the Oil Level

I challenge someone to come up with convincing reason to me that when checking the engine oil there initially isn't any. But if you clean the dipstick and stick it back in and wait 30 seconds and retry there the oil is now full. That on my dipstick is a level change of 1.5" on the dipstick and probably 2 quarts in the engine.

Now I've hear the "the dipstick pulls a vacuum" story before. But I take the fill cap off when I check the oil. But that doesn't explain why there wouldn't have been oil in the dip tube to start with.

Is there some magic antigravity thing going on in the dip tube before you start checking that has made the oil leave. How can the oil level initially be different in the tube than the oil pan (with the oil pan being higher than the tube)

Have at it.
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Old 19-07-2018, 15:11   #2
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Re: Checking the Oil Level

It get an electrostatic negative charge and repels the oil,; when you wipe discharges electrons and the oil will stick?
No idea really.
What puzzles me, is where the level should be because axis angle of mounting.
Last change I got it arse backward for some unexplicable reason.
DS is aft of center.
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Old 19-07-2018, 15:48   #3
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Re: Checking the Oil Level

Unseat the dipstick, to break vacuum, then push in and pull out. Crankcase is under slight vacuum from hose to intake manifold when engine is running. This pulls the oil down inside the tube on some engines.

It's a feature :-)...
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Old 19-07-2018, 15:51   #4
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Re: Checking the Oil Level

Kind of like a diving bell. The dipstick tube goes almost all the way to the bottom of the oil pan. The dipstick itself plugs the tube at top end. When you pull the stick, you loose pressure and oil fills the tube.
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Old 19-07-2018, 16:49   #5
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Re: Checking the Oil Level

Quote:
Originally Posted by sailorboy1 View Post
I challenge someone to come up with convincing reason to me that when checking the engine oil there initially isn't any. But if you clean the dipstick and stick it back in and wait 30 seconds and retry there the oil is now full. That on my dipstick is a level change of 1.5" on the dipstick and probably 2 quarts in the engine.

Now I've hear the "the dipstick pulls a vacuum" story before. But I take the fill cap off when I check the oil. But that doesn't explain why there wouldn't have been oil in the dip tube to start with.

Is there some magic antigravity thing going on in the dip tube before you start checking that has made the oil leave. How can the oil level initially be different in the tube than the oil pan (with the oil pan being higher than the tube)

Have at it.
I'm guessing you have a Yanmar. I have a 4JH and have the same issue. My oil check method is to pull the dipstick out comepletely, then open the oil cap, do my rest of engine check and then come back and measure the oil. The reason this happens has to do with the way the dipstick tube is setup. On a regular car engine the dipstick tub ususally attaches to the side of the block and as a result the dip stick is directly in the open oil pan with lots of air space.

on my yanmar the stock dipstick tube is actually connected to the side of the oil pan (more like a port) so the oil has to migrate out of the pan and up into the tube. When the engine is running my guess is the oil pump is pulling oil away from that area. when the engine is at rest there is a "buffer of air" in the tube preventing the initial reading from bing accurate.

just my guess.
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Old 19-07-2018, 17:15   #6
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Re: Checking the Oil Level

I've had the same issue and now, thanks to you folks, I have an answer. Thanks!

Ahhh, but let me add to the equation. When I do finally get oil on the dipstick it is very light colored, almost like honey. It looks like brand new oil even though I am coming up on my 100 hour change interval. Don't be alarmed, it is black as sin when I change it. But on the dipstick, fairly darn clear!

Any ideas? It must have something to do with the original question by SB1..
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Old 19-07-2018, 17:28   #7
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Re: Checking the Oil Level

Lyle you have the special racist Yanmar.

Not one has convinced me with their dipstick theory.
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Old 19-07-2018, 17:37   #8
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Re: Checking the Oil Level

The new oil in the bottom of the tube doesn't leave until you drain the oil.
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Old 19-07-2018, 17:38   #9
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Re: Checking the Oil Level

The dipstick theory is right. The only way for oil to travel up the tube is to break the seal at the top first.
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Old 19-07-2018, 17:42   #10
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Re: Checking the Oil Level

Describe it using physics and fluid dynamics to explain why the pressure doesn’t equalize.
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Old 19-07-2018, 17:44   #11
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Re: Checking the Oil Level

Quote:
Originally Posted by sailorchic34 View Post
. . . It's a feature :-)...



i.e., not a bug


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Old 19-07-2018, 18:09   #12
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Re: Checking the Oil Level

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Originally Posted by sailorboy1 View Post
Lyle you have the special racist Yanmar.

Not one has convinced me with their dipstick theory.
Ha! I knew there was something to it!
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Old 19-07-2018, 19:39   #13
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Re: Checking the Oil Level

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Originally Posted by sailorboy1 View Post
Describe it using physics and fluid dynamics to explain why the pressure doesnít equalize.
The air between the oil level and the dipstick is "sealed in". As the oil sump drains it lowers the oil level below the tube level. At that point there is no oil in the tube. This is why you check oil level with the engine off. Once the engine stops the tube is full of air and the oil rises in the tube compressing the air. But it can't displace the air because it has no place to exit. The dipstick is sealed at the top of the tube. Some Yanmar dipsticks have a rubber seal at the top. Lots of other brands don't do that.

Try this experiment. Next time you buy a soda with one of those environmentally disastrous straws remove the straw from the cup. Put your finger over the top of the straw and insert it back into the soda all the way to the bottom of the cup. Does the level inside the straw equal the level of soda in the cup? No. Why? Remove your finger. Does the level in the straw now match the level in the cup? Yes. Why?
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Old 20-07-2018, 04:21   #14
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Re: Checking the Oil Level

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Originally Posted by transmitterdan View Post
The air between the oil level and the dipstick is "sealed in". As the oil sump drains it lowers the oil level below the tube level. At that point there is no oil in the tube. This is why you check oil level with the engine off. Once the engine stops the tube is full of air and the oil rises in the tube compressing the air. But it can't displace the air because it has no place to exit. The dipstick is sealed at the top of the tube. Some Yanmar dipsticks have a rubber seal at the top. Lots of other brands don't do that.

Try this experiment. Next time you buy a soda with one of those environmentally disastrous straws remove the straw from the cup. Put your finger over the top of the straw and insert it back into the soda all the way to the bottom of the cup. Does the level inside the straw equal the level of soda in the cup? No. Why? Remove your finger. Does the level in the straw now match the level in the cup? Yes. Why?


This is the reason,
It does not happen in an automobile because the dip stick tube does not go under the oil level. It does in a Marine engine so that the tube can be used to extract oil. You donít have to slide a tube inside of the dip stick tube, you could attach a hose to it instead.
You do not have to remove the oil cap because the engine is vented thru the crankcase vent, the tube connecting the valve cover to your air inlet.
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Old 20-07-2018, 05:18   #15
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Re: Checking the Oil Level

4JH4-TE. I don’t even look at the effing dipstick anymore when I first pull it out. I whipe it, put it back in, wait at least 10 seconds, then I stick the damn thing back in, wait a couple more seconds, then and take it out and read it. I do this about 3 times to assure a consistency reading.

I’m with SailorBoy, makes no sense. That first pull can be anywhere, high or low.
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