Checking the Oil Level

[pcmm]

Originally Posted by hpeer

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.

If you look at the way the dipstick tube is assembled it makes a bit of sense actually. When the Engine is running the oil pump will suck the oil away from the location of the dipstick tube. as the tube is bolted to the side of the pan, oil has to migrate back up the tube. The dipstick cap is a tight fit so the oil would have to compress the air in the tube to reach its level, that's not going to happen. taking the dipstick out removes that restriction allowing the oil to flow up to its level so you can take a reading. Its annoying but that's the was they designed it.

[MV Wanderlust]

Physics, schmysics. It's a social thing, really. Let's walk through this for a second... what is oil? Processed petroleum. Oil pumped out of the ground or the residue of long-dead dinosaurs. It's well-documented that dinosaurs were pack or herd animals, mostly for the safety and social aspects. Now, millions of years later, the residue of Bob the dinosaur meets up in your oil pan with the residue of Steve the dinosaur. Keep in mind how long it has been since they've seen each other so they have lots of catching up to do. All day long for them it's yak, yak, lubricate the crankshaft, yak, yak, lube the piston rings, and yak. Until one day you come along and pull out the dipstick. Now they suddenly see light and realize they've been gabbing for weeks or months and are really hungry. They've heard about this new thing called "hot dogs" and decide to head out to get some. Dinosaurs were huge and the dipstick tube is small so it takes them a while to start their way up the tube... only to get poked in the eye by you, trying to get a reading on some long metal strip. When you think about it, you're being pretty rude and inconsiderate of the animals that were here long before you. In this day and age of being ultra-pc, perhaps it would be best to just stick to checking the oil gauge.

All you folks talking about pressure equalization and stuff probably feel pretty foolish right about now, dontcha?

[Suijin]

I think SailorChic gave a pretty clear explanation, dunno why SailorBoy won’t accept it.

Pull stick, push back down, if it comes back up with oil on it it’s pretty clear what’s going on. No fancy fluid dynamics discussion required.

[pcmm]

Originally Posted by JohnEasley

Physics, schmysics. It's a social thing, really. Let's walk through this for a second... what is oil? Processed petroleum. Oil pumped out of the ground or the residue of long-dead dinosaurs. It's well-documented that dinosaurs were pack or herd animals, mostly for the safety and social aspects. Now, millions of years later, the residue of Bob the dinosaur meets up in your oil pan with the residue of Steve the dinosaur. Keep in mind how long it has been since they've seen each other so they have lots of catching up to do. All day long for them it's yak, yak, lubricate the crankshaft, yak, yak, lube the piston rings, and yak. Until one day you come along and pull out the dipstick. Now they suddenly see light and realize they've been gabbing for weeks or months and are really hungry. They've heard about this new thing called "hot dogs" and decide to head out to get some. Dinosaurs were huge and the dipstick tube is small so it takes them a while to start their way up the tube... only to get poked in the eye by you, trying to get a reading on some long metal strip. When you think about it, you're being pretty rude and inconsiderate of the animals that were here long before you. In this day and age of being ultra-pc, perhaps it would be best to just stick to checking the oil gauge.

All you folks talking about pressure equalization and stuff probably feel pretty foolish right about now, dontcha?

Here and I thought you were going to talk about the "micro-aggressions" of inserting a dipstick into an oil pan that didn't consent, triggering a harm in what was the "safe-space" of the dipstick tube!

[jimbunyard]

If they're orings on the ring end, pull them off and see if it changes things. If the end seals with a hard rubber stopper kind of arrangement, cut a little groove to let air in...

[a64pilot]

Don’t break the seal on the dip stick, unless you don’t mind oil coming from it, the engine builds slight pressure from blow by, it’s relieved through the crankcase breather of course, but it can also come out the dipstick tube, this is why it’s sealed, to prevent that.

There is nothing broken, nothing to fix

[jimbunyard]

So which is it? The engine pulls a vacuum to seal air into the tube or it has crankcase pressure that blows oil out of the tube? It can't be both.

[MV Wanderlust]

Originally Posted by pcmm

Here and I thought you were going to talk about the "micro-aggressions" of inserting a dipstick into an oil pan that didn't consent, triggering a harm in what was the "safe-space" of the dipstick tube!

Oh, that's good!

[StuM]

Originally Posted by jimbunyard

So which is it? The engine pulls a vacuum to seal air into the tube or it has crankcase pressure that blows oil out of the tube? It can't be both.

It is both!


The former when the engine is shut down, the latter when the engine is running.

[a64pilot]

Originally Posted by jimbunyard

So which is it? The engine pulls a vacuum to seal air into the tube or it has crankcase pressure that blows oil out of the tube? It can't be both.

I don’t believe the engine ever pulls any kind of vacuum.
However one end of the tube is sealed, it is heated and cooled, as it does this of course the air trapped in the tube will either expand or contract depending on temp.

It is the thumb on the straw example, the stick is your thumb.

Don’t believe us, remove the stick, blow into the tube listen for bubbles, or suck on it and see if you get a mouth full of oil.

[hpeer]

Sometimes it reads high, sometimes it reads low. If I measure 3 times I quick succession I get 3 different readings.

That’s why I check 3 times with a 10 second wait between.

I NEVER feel confident.

[EmeraldCoastSailor]

I like this "feature" of my Yanmar.

[Stu Jackson]

Originally Posted by EmeraldCoastSailor

I like this "feature" of my Yanmar.

We have them on M25 and M35 Universal engines, too.


It is usually the very first thing we have to explain to our new skippers.

If they're orings on the ring end, pull them off and see if it changes things. If the end seals with a hard rubber stopper kind of arrangement, cut a little groove to let air in...

a64 is right, don't ever do that. Ever. When I bought my boat is was "only" 12 years old. First thing I had to do was replace the dipstick, it was leaking 'cuz the rubber seal was deteriorated. Just last week my friend with the same engine I have had an oil leak MESS. We had to DUCT TAPE his dipstick to the tube to stop it. Small leak, BIG mess.



I'm an engineer, but I believe in "the use of the available," meaning it sometimes matters little in the real world as to why things happen, just that it does and there's a simple actionable solution. I don't take mine out three times, I just pull it up maybe three inches, go do something else for a bit come back, reinsert, and then read it, never take anything else off. I have this handy little door for access to it, so I don't have to take anything else apart.


In the 20 years I've had this boat with a diesel engine, I've read everything ever written on this subject, but I just counsel others to do what works, rather than figuring out or explaining why. I used to want to know why about everything, ever since I was a kid. Remember when I kept asking Mom why, why, why? all the time? She eventually taught me to stop!



That said, next time somebody asks, I'm goin' with the Steve and Bob The Dinosaur story.

[jewt]

And I thought it was only MY problem!

jewt

[jimbunyard]

Really love when people start applying absolutes to things they have no reason to know the 'absoluteness' which they're specifying.

If your engine is blowing oil out the dipstick tube, there is a high probability that there is something wrong with it other than intermittent dipstick readings.

Don't think this is Sailorboy's case; the 'vacuum excuse' seems to fit the physical requirements best, it is actually a non-problem that is best resolved by checking the oil in a manner that reflects that need.

But if it's one of those things that just erks, then removing the orings or leaving the dipstick out while running it a while is just a diagnostic tool to see if this is actually the case. For some it appears that a slight modification of the dipstick stopper is a major event; for those they have 'professional' mechanics who can be easily consulted...

As for the heat vs vacuum question, unless there is some sort of check valve in the crankcase ventilation system, and there may be, and it should be checked that is clean and operational, it seems to me that oil would be drawn up into the dipstick tube by cooling (shrinking) air, not pushed out.

But of course this is a dynamic system of which I don't know the full conditions, so I have to remain with the preface "seems to me".