Does Removing Oil Filler Cap Release Vacuum?

[JerryBob]

One of the few things I remember from college is that if you punch a hole in the bottom of a beer can, you can chug it very quickly.

So, I always remove the oil filler cap before draining oil.

But does this really help? Is there even an air passage between the valve covers and the oil pan, such that air displacement would take place?

 

[spasm3]

I don't think its a closed system. The pcv system is a vent to the intake. Air gets in through the idle circuit.

 

[simple_gifts]

Quote:

Is there even an air passage between the valve covers and the oil pan, such that air displacement would take place?


Yes, that is how the cold oil you pour in the valve cover during an OC gets down there.... 8)

 

[JerryBob]

Originally Posted By: simple_gifts
Quote:

Is there even an air passage between the valve covers and the oil pan, such that air displacement would take place?


Yes, that is how the cold oil you pour in the valve cover during an OC gets down there.... 8)


Ok. Yeah, that makes sense

 

[Chris142]

The engine is vented already.

 

[eljefino]

There's usually a 3/8" fresh air hose between valve cover and an intermediate part of the air intake tube as part of the PCV system. The diameter of your drain hole is about 3/8", and even if it's more, like 1/2", air is less viscous than oil and will find its way in.

 

[abycat]

I always pull the dipstick out when draining or filling. Some manufacturers say oil will contaminate pcv system if you don't.

 

[CT8]

Originally Posted By: abycat
I always pull the dipstick out when draining or filling. Some manufacturers say oil will contaminate pcv system if you don't.
How so?

 

[zpinch]

I am not sure you should be near an engine if you don't know if there are passages from valve-train into the sump... no offense.

 

[simple_gifts]

Originally Posted By: zpinch
I am not sure you should be near an engine if you don't know if there are passages from valve-train into the sump... no offense.


You are ridiculing a person who is trying to learn; classy.

 

[Eddie]

Oil drains from my Mazda speeds up considerable when I loosen the fill cap. Did the same with my Subaru. ed

 

[abycat]

Originally Posted By: CT8
Originally Posted By: abycat
I always pull the dipstick out when draining or filling. Some manufacturers say oil will contaminate pcv system if you don't.
How so?


not sure but it says in my service manuals. Only for filling.

 

[zpinch]

Originally Posted By: simple_gifts
Originally Posted By: zpinch
I am not sure you should be near an engine if you don't know if there are passages from valve-train into the sump... no offense.


You are ridiculing a person who is trying to learn; classy.


Hey, maybe he should learn the basics first, before getting hands on, that would be classy.

 

[Bud]

One thing nice about these forums is that there are all kinds of folks here. One may know a lot about cars and engines, and others may be just interested or learning. There is no such thing as a dumb question, its only dumb if you don't know and don't ask for an answer. No one should be ridiculed for asking any question here.

 

[spasm3]

Originally Posted By: Bud
One thing nice about these forums is that there are all kinds of folks here. One may know a lot about cars and engines, and others may be just interested or learning. There is no such thing as a dumb question, its only dumb if you don't know and don't ask for an answer. No one should be ridiculed for asking any question here.


Well said!

 

[Nyati]

Originally Posted By: spasm3
Originally Posted By: Bud
One thing nice about these forums is that there are all kinds of folks here. One may know a lot about cars and engines, and others may be just interested or learning. There is no such thing as a dumb question, its only dumb if you don't know and don't ask for an answer. No one should be ridiculed for asking any question here.


Well said!


+2

 

[Leo99]

Originally Posted By: Nyati
Originally Posted By: spasm3
Originally Posted By: Bud
One thing nice about these forums is that there are all kinds of folks here. One may know a lot about cars and engines, and others may be just interested or learning. There is no such thing as a dumb question, its only dumb if you don't know and don't ask for an answer. No one should be ridiculed for asking any question here.


Well said!


+2


One can perform all the necessary preventive maintenance on a car without knowing the intricacies of an internal combustion engine.

 

[raytseng]

yes, it definitely makes a difference in a modern car but only for specific situations.

When I use use an oil extractor to do an oil change via the dipstick-especially with a decently close sized tube you immediately can notice you have problems extracting unless you undo the fill cap, which will then hiss. At least in my cars that are in proper condition. (toyota 1UZ, 2JZ, engines). You can definitely tell it's a closed vaccuum system when my cars are off.

IF you are doing the standard oil change via the plug, that is large enough so I suppose it'll just glug/shoot out.
You can imagine turning over a bottle with a straw it's just going to dribble, but turn over your widemouth snapple, doesn't matter.

 

[turtlevette]

Originally Posted By: zpinch


Hey, maybe he should learn the basics first, before getting hands on, that would be classy.


It shows that he's thinking and that's not a bad thing.

In racer systems where you have dry sump, everything IS sealed up so they can draw a vacuum. The vacuum gains them a few HP eliminating crank windage, and piston displacement of air.

 

[aquariuscsm]

I actually always wondered this very same thing years ago. I'd always remove the oil fill cap when draining the oil for an oil change.

No question is a dumb question JerryBob. That's how we learn,by asking questions.