Vacuum problem in valve cover

[Relic23]

94 corolla. I had the oil cap off and the engine on and oil was flying out from the hole in the valve cover. Shouldn't there be a vacuum. There is also a loud noice comin from inside the valve cover.

[iToaster]

The vacuum is in the intake (because that's where the engine sucks the air in), not the valve cover. Oil will spew out of it because the oil pump is forcing it up there. That noise is probably the cam shafts opening and closing the valves. Everything is as it should be.

[jelly53]

yup, during the oil change I opened up the cap while the engine was running to put some Motor Flush, and the oil started coming out.

[Hook]

ummm...you're supposed to put the flush with the engine off, then start up and let it idle for however long the instructions say, before you switch off and drain the old oil.
That way you don't make a mess of things or risk burning yourself with hot oil.

[jelly53]

ya I knew that LOL...... but I figured if put it in while the engine was running....it would mix in better.... but it didnt work out!

[speedy25]

There is nothing pressurized just under the valve cover. Oil splashes out because there is a pool of it under the cover and the spinning cams splash it around. The small amount of vacuum created by the PCV system is more than overcome by the large oil cap hole.

-SP

[fast68]

some engines wont run or run very well when the cap is removed, i have found... many times in the past.


some toyotas i know.....

and others..

[BoyYota]

I saw a guy tell a story once, think it was on the Nissan forums or maybe VW forums (I've had a lot of cars), how he ran his car without the oil cap on (by accident--woops!(?)). He said 'well now I know that running without an oil cap on will destroy an engine!' D'oh! I know that you weren't doing long term, but still, this isn't some diesel military application, you don't change the oil with the engine running!