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PCV Valve

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AlaskaCJ2A View Drop Down
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    Posted: 11 Mar. 2007 at 5:02pm
Next question -
 
I have a AC 1543018 PCV valve.  When I do a suck/blow test on it, should it act as a check valve would, or is that even a valid test?  What are the guts of this thing? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lowenuf Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 7:18pm

yes, it should act as a check valve, the old saying is "if you can shake it, and it rattles, it is good"... vacuum will push/pull the thing inside to close/open the travel...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote CJ3A Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 8:53pm
Mine does nothing, but is not clogged (the guts are missing).  Is it necessary, and what would happen if I did not have one?
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lowenuf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lowenuf Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 9:23pm
As an engine runs, the crankcase begins to collect combustion chamber gases which leak past the rings surrounding pistons and sealing them to the cylinder walls. These combustion gases are sometimes referred to as "blow by" because the combustion pressure "blows" them "by" the pistons. These gases contain compounds harmful to an engine, particularly hydrocarbons, which are just unburned fuel, as well as carbon dioxide. It also contains a significant amount of water vapor. If allowed to remain in the crankcase, or become too concentrated, the harmful compounds begin to condense out of the air within the crankcase and form corrosive acids and sludge on the engine's interior surfaces. This can harm the engine as it tends to clog small inner passages, causing overheating, poor lubrication, and high emissions levels. To keep the crankcase air as clean as possible, some sort of ventilation system must be present.

Edited by lowenuf - 11 Mar. 2007 at 9:25pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WILLYS2A Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 9:37pm
Hey low
fantastic explanation I like to call this the readers digest explanation because even a dough head like myself can fully understand it thanksTongue
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lockdowns Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 10:09pm
You just read that out of an Apex Technical School manuel... didn't you?Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lowenuf Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 10:14pm

I know a thing or two about Longaberger Baskets also, care to hear about why they use maple instead of oak?  lol 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote lockdowns Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 10:19pm
You know what they say, Knowledge is power!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GaryArf Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 10:42pm
I thought that maybe you stayed at a holiday in last night LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Joe IA Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 10:49pm
Low,
 
You've been to Dresden too, haven't you?
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lowenuf Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar. 2007 at 11:19pm
Originally posted by Joe/IA Joe/IA wrote:

Low,
 
You've been to Dresden too, haven't you?
 
 
 
one too many times..lol  however, it IS I that collects the older baskets, not the mrs..Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bluax Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar. 2007 at 10:42am
I've been looking for a new one for quite awhile ... any suggestions?
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlaskaCJ2A Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar. 2007 at 9:51pm
Ok, so the PCV acts as a "check valve", allowing vapors to flow from the crankcase (valve cover fitting) to the intake mainifold, but not the reverse.  One should hear a "rattle" if the guts are present and free moving.
 
When I performed the "suck/blow" test on mine, air was free to move either direction and there is no "rattle" sound, indicating that either the guts are missing, or jammed up by gunk.  So, either I need a new one, or..........
 
Here is my theory, please don't hesitate to blow it out of the water if you disagree:
 
When the engine is operating, the pressure inside the manifold is less than atmospheric, creating a suction in the PCV line and pulling air from the crankcase to create positive crankcase ventilation.  That being the case, when, if ever, would air be able to move the opposite direction towards the crankcase during engine operation even if a PCV were not installed?  In other words, as long as the line is attached and clear, is the "check valve" function of the PCV even necessary for correct operation of the system? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lowenuf Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar. 2007 at 10:05pm

The PCV valve is only one part of the PCV system, which is essentially a variable and calibrated air leak, whereby the engine returns its crankcase combustion gases. Instead of the gases being vented to the atmosphere, gases are fed back into the intake manifold, to re-enter the combustion chamber as part of a fresh charge of air and fuel. The PCV system is not a classical "vacuum leak."  The PCV system just diverts a small percentage of this air via the breather to the crankcase before allowing it to be drawn back in to the intake tract again. It is an "open system" in that fresh exterior air is continuously used to flush contaminants from the crankcase and into the combustion chamber.

The system relies on the fact that, while the engine is running, the intake manifold's air pressure is always less than crankcase air pressure. The lower pressure of the intake manifold draws air towards it, pulling air from the breather through the crankcase (where it dilutes and mixes with combustion gases), through the PCV valve, and into the intake manifold.

The PCV system consists of: 1) The breather tube , and 2) The PCV valve. The breather tube connects the crankcase to a clean source of fresh air, such as the air cleaner body. Usually, clean air from the air cleaner flows in to this tube and in to the engine after passing through a screen, baffle, or other simple system to arrest a flame front, to prevent a potentially explosive atmosphere within the engine crank case from being ignited from a back-fire in to the intake manifold. The baffle, filter, or screen also traps oil mist, and keeps it inside the engine.

Once inside the engine, the air circulates around the interior of the engine, picking up and clearing away combustion byproduct gases, including a large amount of water vapor, then exits through a simple baffle, screen or mesh to trap oil droplets before being drawn out through the PCV valve, and into the intake manifold.

 
wow, my fingers are tired now.....lol    hope this clarifies....low


Edited by lowenuf - 12 Mar. 2007 at 11:33pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote westforkwillys Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar. 2007 at 10:45pm

Joe,  Cedar Falls huh?? Good to see the Iowa  contingency is growing.  Live about 15 miles northwest of you down on the river bottom.  I think you can probably tell which river.Wink  Anyway welcome to the site, you will find lots of great people with TONS of knowledge here.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote westforkboyd Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar. 2007 at 11:31pm
This is getting interesting. Doesn't the fresh clean air enter the crankcase from the crossover tube from the air breather through the dipstick tube?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlaskaCJ2A Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar. 2007 at 11:32pm
low, nice description of the system, man,  but back to my question / theory - is the "check valve" function of the PCV valve even that necessary for proper system operation as long as the line is clear?  Bottom line - I'm trying to figure out how crucial it is for me to replace it - my parts list is already long and spendy!
 
Right now I've got it soaking in my tank, hoping maybe to loosen the gunk I theorize is inside and restore the "rattle" - then this would be a moot point.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lowenuf Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar. 2007 at 11:40pm
well, i must say 1st...WFB....i corrected my mistake in the typing about fresh air from the manifold :)
 
2nd. when i mention "rattle", i am referring to the pcv valves that i put in big block chevys...i guess the 2a valve might not rattle to verify if it is good or not..
 
Tony, i suppose your "theory" would have merit, i would rather think of it this way...
 
you put a check valve on a sump pump for a reason, would that system work effectively/effeciently without the check valve in place? 
 
without the pcv in place, i do not see the weaker negative pressure in the manifold pulling the greater negative pressure in the crankcase up, and into the manifold to redistribute it back through the combustion chamber, at least not effectively...
 
engine will run, crankcase will build pressure, but without the pcv in place, the system in theory would have equal internal pressure, therefore not evacuating ALL of the nastys in the crankcase area..
 
 


Edited by lowenuf - 12 Mar. 2007 at 11:45pm
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