Pressure/Vacuum in crankcase

[TRUEBLUEMAX]

I am in the process of putting a K&N kit on my Nytro. I have the main filters on but not the breather filters yet. I started it last night to listen to the new exhaust system I just put on and when I shut it down it was making a whistling noise. Found that it was coming from the small vent line that goes to the valve cover. The noise lasts for probably close to thirty seconds. Did it both times that I started it.

Any ideas? Doesn't seem right to have any kind of pressure or vacuum on the crankcase like that. Love to hear your thoughts on this.

 

[twincam88]

mine does this as well with the little vent on the line maybe not enough flow? been riding with it for 2 seasons now and no problems though!

 

[paulharris]

shouldn't be any vacuum?? there absolutely is vacuum inside that valve cover so that is probably what you are hearing. that is a small valve cover vent

 

[TRUEBLUEMAX]

It just seems to me that is a long time to have that much vacuum on the engine. I don't know how they are able to get that much vacuum on the engine, or is that just part of the dry sump system working that way. Does it put a vacuum on the engine to pull the oil into the tank? I thought it was just a gravity feed system to get the oil into the tank.

I guess if I am not alone on this then fine, but it just seems odd that there would be enough vacuum to do that.

 

[MTN_VIPER]

The hose going to the valve cover is part of the PCV system.

The way that the oil supply system works, is the oil pump has two halves to it. The pressure supply half of the pump draws oil from the bottom hose of the tank and feeds the oil pressure to the various bearings/componets inside the engine.
As the oil drains back down into the bottom of the crankcase, the scavage half of the pump draws oil from the bottom of the engine and pumps it under pressure back to the oil tank. The return hose is the one that connects to the oil tank about half way up.
The system is called a dry sump lubrication system because the oil pump is constantly scavaging oil from the bottom of the engine keeping it more or less "dry".

Bill

 

[towerrigger]

Last year I snapped the elbow off of the valve cover breather. I can see how it would make a whistling sound. The size of hole in that elbow that is pressed into the valve cover is very tiny. Be careful with that elbow as it is cast and mine snapped easily.