Topic: Can someone check something for me?

[Bounty Hunter]

IMO both hoses are part of the CCV system, and vapors/air should travel in the same direction ALL the time.  The manifold pulls crankcase vapors from the front of the valve cover.  The crankcase in turn pulls fresh air from the airbox.  It's that simple.  If anything travels from the rear of the valve cover into the airbox, it's wrong.  IMO.

I run an aftermarket cam, which you would think would pull a little less vacuum than a stock cam, and I've never seen any oil from the tube at the back of the valve cover.

[neale_rs]

Same here, no oil in the fresh air tube, ever.

[Jeffy]

If the CCV is clogged it will flow out the Fresh Air Vent.  The CCV is just a passthrough brass fitting unlike the older ERG valve on older engine.  BTDT.

Also, if you thin thinner oil, you'll tend to get more blow by.

[Bounty Hunter]

I read it.



The scroll.

[Rob the plumber]

The tube that goes to the airbox is most definitely intended to draw vapors from the valve cover and draw them back through the intake. That line will have suction on it all the time from the airbox, which will increase with engine load/less vacuum when the CCV line connected to the manifold stops drawing at zero vacuum.

Basically, at ldle the manifold line is doing the fair share of work. The "airbox line" is not drwaing much if anything.
At high load and some RPM's, the manifold line will have zero vacuum and no longer pull, The engine is then trying to breathe like crazy and pulls a decent amount of air from the airbox tube.

This is a very basic concept. Old school 5.0L Mustang tech here. It is how a engine evacuates the crankcase under boost as well. (once you add a check valve to the manifold line anyway...)

[Bounty Hunter]

I don't think the manifold ever has 0 vacuum, and the airbox line should never pull towards the airbox.

[jfrabat]

I dont think it will read 0 either, but it can be vey low when at highway speed and under load (as going uphill or against the wind).  I first noticed the effect when driving with the AC under these conditions, as the vent would suddenly start blowing outside air throught the defroster (this was fixed with a small vacuum reservoir, but the effect would be the same for the CCV I think).

[Rob the plumber]

I don't think the manifold ever has 0 vacuum, and the airbox line should never pull towards the airbox.

Put a gauge on it and see for yourself.  You think that the crankcase draws vapor in from the airbox then? How is that possible when there is always positive pressure in the crankcase?

[Bounty Hunter]

Put a gauge on it and see for yourself.  You think that the crankcase draws vapor in from the airbox then? How is that possible when there is always positive pressure in the crankcase?

Because the crankcase vents into the intake manifold.  It's a continuous cycle to burn crankcase vapors.  You don't lose all vacuum at WOT.

[Rob the plumber]

Ok. :)

[countryboy514]

the air box line is called "port vacuum" which will increase with air flow. at idle with the throttle closed, vacuum in the manifold is high called "manifold vacuum", when the throttle is opened the manifold vacuum drops as the port vacuum increases due to the increase of air flow in the intake tube. the crankcase is designed to be under vacuum at all times. when at idle, manifold vacuum draws from the crankcase. during acceleration port vacuum takes over and draws from the crankcase via the air box line. the problem is the 2.5l motor does not draw enough air from the crankcase and blowby causes pressure in the crankcase.