PCV valve problems...

[HISSIN50]

first time i did it, i pushed myself up on the engine bay from the drivers side. laying across the engine bay, you can look down and see what you are doing (rest chest or arm on the upper. LOL).

the grommet pulls right out. the screen has some tabs on the inner circumference. i use a pair of LONG needle nose pliers to grab onto one of these tabs. you could use a crochet hook type of something to pull it out too. they can like to stick some.

thats all i did. now you see why its nice to do right once and forget it for two years (thought next time its super easy).

good luck.

 

[88mustang_5.0sb]

I have disconnected the line that runs from the oil filler on the passenger side valve cover to the upper intake manifold. I installed a breather filter on the oil filler tube side and a plug on the intake side. Does this block the flow of air from the engine to the upper intake thru the pcv? And if so should I plug that line somehow? Help!

 

[88mustang_5.0sb]

Anyone? Should I put another breather on the PCV side or leave it?

 

[Michael Yount]

You don't have to see it to remove it in my experience. Just reach down -- if you can feel the grommet - you should be able to pull it out. Once it's out, just stick a magnet/wand down in the hole. The manifold is aluminum - the screen is steel. The magnet will pick up the screen and pull it out.

 

[88mustang_5.0sb]

That didn't answer my question. Should I vent my pcv to the atmosphere or allow it to be routed back into the upper intake?

 

[Michael Yount]

I was responding to 90silverstang's question.

When the manifold is under vacuum, it pulls air in from the crankcase through the pcv valve. This air has to enter the engine from somewhere. It's designed to enter through the hose you removed. That way, the air has been metered through the maf before passing through the crankcase to the intake manifold. At w.o.t. when there is no vacuum, and plenty of crankcase pressure - it gets vented both through the pcv valve, and through the line that runs from valve cover to throttle body. That hose (which you removed) is bi-directional. With a breather there instead, air can still enter the crankcase (under vacuum being pulled in via the pcv line) and can vent to atmosphere at w.o.t. However, now, whenever you have vacuum conditions in the manifold, you are pulling unmetered air into the engine through the breather. Hard to say how much of a problem that is.

Why would you want to vent the pcv to atmosphere? Why did you remove the hose in the first place? I'd think that any self-respecting CA emissions inspection tech would bust you on a visual the minute they saw the breather under the hood. But perhaps I've giving them too much credit.

 

[88mustang_5.0sb]

Thanks for the response. You are correct that I'm sure it wouldn't pass the smog visual at this point. From what I had read you can put a breather on the oil filler tube end and not have the recirculated air flowing back thru the intake so as not to gum up the intake manifold. I was thinking of allowing the pcv to vent to the atmosphere for these same reasons. I have a special valve that doesn't allow air to come back into the engine thru the pcv so it would have to be sucked in thru the intake or the breather on the passenger valve cover. Just wondering if anyone else has tried this set up.

 

[Michael Yount]

"From what I had read you can put a breather on the oil filler tube end and not have the recirculated air flowing back thru the intake so as not to gum up the intake manifold." That's inaccurate. By putting the breather on the filler neck you simply cause the air that gets pulled into the intake through the pcv to be unmetered, and any crankcase venting that goes on (w.o.t. for example) will simply be to atmosphere instead of back into the throttle body. Some crankcase venting will still occur through the pcv valve under those same conditions (w.o.t.).

You are correct - if you vent both the valve cover and the pcv to atmosphere, nothing will be drawn into the intake from the crankcase. Technically, you won't have "PCV" (positive crankcase ventilation) any longer. You'll just have your crankcase vented to atmosphere. All pcv valves prevent flow from the intake to the crankcase; they are nothing more than a check valve which only allows flow from the crankcase to the intake. Back in carb'd days, you had a mixture of gasoline and air in the manifold, and getting that explosive mixture pulled into the crankcase could result in a crankcase explosion - not pretty. Hence the 'check' pcv valve.

A properly operating pcv system shouldn't deposit excessive amounts of oil in the intake. When that's happening it's usually because of one or all of the following 1) the oil trap screen under the pcv is clogged up; 2) the pcv valve is malfunctioning (clogged up usually); 3) the engine has excessive crankcase pressure due to blow by (high mileage, failing rings, VERY high cylinder pressures due to nitrous or boost.

But, venting the crankcase to atmosphere will eliminate all possibility of oil in the intake. If you're suffering from excessive amounts in the intake, venting to atmosphere usually makes a heckuva mess over time - that oilly vapor gets all over everything over time. Good luck with it.

 

[88mustang_5.0sb]

Good info. How about if I put a pcv type valve on the valve cover as well? This would stop the unmetered air from coming in that way but would still allow the pressure to be relieved. Would this work? It would not solve the problem of the oily air being routed to the engine compartment instead (as you pointed out)... Also why is there ventilation on the passenger valve cover but not the driver's side?

 

[Michael Yount]

If you stop allowing air to enter the valve cover when the pcv is pulling on the crankcase, it will create a vacuum condition in the crankcase. It might take a bit of time for it to show up, but you'll start to hear squealing sounds as air gets sucked into the crankcase across the front and rear crankcase seals -- not good for the seals. If you're gonna have the intake pulling on the crankcase, you need a path for air to enter the crankcase. That's what the valve cover fitting is for. You only need a fitting on one valve cover because all the area under both valve covers is essentially common - those spaces are all connected by the openings in the head for pushrods and oil drainback.

 

[88mustang_5.0sb]

I think I'm coming full circle on this now. Air enters the crankcase thru the tube from the tb/intake to the valve cover and exits thru the pcv back into the upper intake. So in order to not have the oily recirculating air in the intake I'd need to vent the pcv to the atmosphere. I need positive airflow from the outside world into the crankcase to prevent this blow-by (or whatever you want to call it). Does air ever circulate back into the upper intake thru the valve cover tube or is there a valve in there that prevents this? This has been a great help Yount. Brian

 

[Michael Yount]

"Does air ever circulate back into the upper intake thru the valve cover tube..."?

From my first post above -- "At w.o.t. when there is no vacuum, and plenty of crankcase pressure - it gets vented both through the pcv valve, and through the line that runs from valve cover to throttle body. That hose (which you removed) is bi-directional." Air flows both ways through that hose - when vacuum is present, it flows from throttle body to valve cover. When crankcase pressure is present it flows from the valve cover to the throttle body. There is no valve or restriction to prevent it -- by design.

 

[Michael Yount]

For what it's worth, I left my system intact; however, I installed catch cans in between the pcv valve and the intake, and in between the valve cover nipple and the throttle body. Each line has a small see-through fuel filter in it to help knock oil out of the hose, and it drops into the catch can minimizing the oil that can be picked up by the intake or throttle body. Oil in the intake is minimized, and the whole system is still emissions legal and keeping oil mist out of the atmosphere. Email me at [email protected] - I might have a pic or two that shows it.