How to verify a good crankcase pressure?

[maxiz1]

I think I just wasted $50 for a replacement of the UFO PCV valve, the PCV valve under the intake manifold as well as the T-connector. I'm currently having a slight oil leak but would like to fix any potential clogging in the crankcase system prior to replacing any seals or gaskets.

So my car had 150K miles. What i noticed before was that the oil cap was "dancing", and air what "puffing" out of the oil cap hole. I checked the SJP and it was ok. Then after replacing both PCV I noticed that the oil cap is still dancing. This is contrary to some of the youtube videos that shows that there should be vacuum in it when tested using a rubber glove.

Can I have an opinion on this please?

[Davdraco1]

I would take tall the houses off and clean them if it worries you. Shouldn't take too long to remove. just run a bunch of degreaser through them and watch the crap come out. just watch you dont crack any of the hardpipes and rubber "joiners", they like to crack.

[maxiz1]

Yes I appreciate the advise. But my question is how to verify the crankcase condition? Do you get the oil cap dancing like mine as well?

[biketsai]

It should not be dancing. How is the vacuum going to the intake manifold from the block breather?

[Davdraco1]

There should be vacuum in the crank case. The blow by from the cylinders should make it have positive pressure, not negative. And what do you mean by dancing? There's is a gasket for the oil cap that makes it snug to the valve cover.

[maxiz1]

Sorry I forgot to state that it "dances" when I loosen up the oil cap during idle. Same as per this video: https://www.youtube.com/watch?v=dsBbaMJoJ-U

The crankcase is connected to the manifold via PCV valve and SJP. Checked SJP.. no clogs. Checked lines.. no clogs too. Changed PCV and UFO valve to new one. Still dancing though.

[Avant Nate]

Forgive me if I'm wrong, but I'm going to assume you have an AEB engine, therefore no vent in the valve cover. So how could there be vacuum? My cap flutters a little bit, but nowhere as much as the video. But I don't know if that means anything is wrong.

[Davdraco1]

It's dancing because there is positive pressure in the crankcase and valve cover area. I imagine that's normal. I thought it was doing that when it was tight.

[maxiz1]

I have an APU engine which is equivalent to the US ATW. Yes no vent on the valve cover but there is on the crankcase.

I guess if everybody else is experiencing this dancing/flutter then I have nothing to worry about.