I was doing some work under the hood today and went to look at pcv valve. There apear to be two connections for hoses and only the bottom nipple has a hose connected to it. cannot find a loose hose.
Can someone tell me what hose should be connected to the top nipple and/or what should that hose connect to.
I am getting oil in the throttle body and heard that a non-functioning pcv valve can cause this. But had bad oil leak from push rod cover gasket about a month ago and wondering if maybe it is just remnants from that. I cleaned the Idle air valve today but didn't have time to pull TB....will clean that in the next couple of days but would really like to know the source of the oil.
Since I'm at it...can someone tell me the purpose of the other hose from the air filter box to front of valve cover.
Thanks for any help
Dave

 

Most PCV valves have two connections on them. The larger one on the bottom connects to manifold vacuum; it is responsible for feeding the valve. The smaller one on top simply acts as a handy tap for something needing manifold vacuum nearby. Often, it is just plugged and not needed. If you don't have any stray vacuum lines dangling around or anything that has been disabled then you can simply just plug it. Just don't leave it open.

Oil in the throttle body can be caused by a bad PCV valve - it's called blow-back or blow-by. Also verify that the breather filter is clean as this can cause that sort of problem too. 9 times out of 10 you can check a PCV valve by taking it out and shaking it. If you hear it rattle then it's okay. But if yours is really old, they are so cheap to replace that you might as well go ahead and do it while you're in there.

That other hose going from the air filter to the valve cover is one of the PCV hoses. The PCV system's job is to keep the air inside the enging crankcase moving. When the engine is running, combustion fumes can escape past the piston rings, which is normal, and would contaminate the oil if left alone. The PCV system circulates these fumes back into the combustion. On the tail end of the PCV system is a breather filter that provides incoming air to the system. The PCV valve shuts the system off under periods of low vacuum. That hose you are seeing is just part of that link.

 

The only time the pcv valve actually shuts off is when there is a carb backfire and that is to prevent any fumes inside the engine to ignite.

You can see the cutaway of a pcv valve and the tapered valve. As more vacuum is applied the taper raises in the seat and there is less flow. As rpms increase the taper is lower and there can be more flow, but the vacuum is also less.

In otherwords, buy the correct pcv valve for the engine it is calibrated for and keep the other hose to the air filter (intake for pcv system) clean.

 

Hey thanks for that...I had checked online and pics show the same pcv valve...I will definitely look into that further. The current valve is good and the 2nd port on it is closed. As for the fresh air hose from breather...I took it off today and cleaned it. It had moisture in it as I was able to blow out water from the line...not much mind you, but I would think that it should not contain moisture at all.(???)

 

Just because a PCV valve rattles doesn't mean it's good. If it doesn't rattle it is definitely bad, but if it rattles it can still be bad.

 

You know...for the few buck it will cost me to replace it, I think It would be wise to change it anyway. It does rattle but is likely old like everything else on the truck and I have done two oil changes since I bought it a few months ago in November.
Thanks for the advice
Dave