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Location:
Adelaide
Registered:
July 2002
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PCV thingo
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Mon, 14 October 2002 17:44
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Okay on my 4ac there are two hoses coming off the rocket cover ones the oil breather and when the engine is running it well breathes like blows some air out and stuff. the other one is sucking in air like mad and the engine idles really badly up and down up and down and almost stalls when this is left open, when i stick my thumb on it the engine idles fine, its connected to this weird looking plastic umm regulator thing in the black metal air cleaner, as im replacing this air cleaner with a chrome rice jobbie i was wondering what exaclty this hose/pcv thing does i know it stands for positive crankcase ventilation but what does that mean? can i just stick a bolt in there or could that cause a pressure build up in the head and lead to a blown head gasket? Also what is the plastic thingy in the air cleaner, what does it do, is it pressure regulated so that when a certain pressure is in the crankcase it opes up and vents it back into the carby?
Cheers
Calum
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Location:
Adelaide
Registered:
July 2002
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Re: PCV thingo
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Tue, 15 October 2002 16:18
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Come on someone has to know what happens if i plug this hose with a bolt.
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I supported Toymods
Location:
melbourne.victoria.austra...
Registered:
June 2002
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Re: PCV thingo
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Tue, 15 October 2002 21:01
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i tried blocking it up - the hose that goes to the inlet manifold, yes block that off - no issue there. put a little breather or something on the point where it comes out of the cam cover - if you block it like i did on my old holden 202 and rev the motor stand out of the way of the dipstick as it fired across the driveway.... 
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Location:
Edmonton, Alberta, Canada
Registered:
October 2002
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Re: PCV thingo
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Tue, 15 October 2002 23:08
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The PCV valve is an emissions control valve. Its purpose is exactly what the name suggests. It ventilates the fumes and blow-by gases from your crankcase and sends them back into the airstream via the air cleaner. That way the fumes are burnt up during combustion instead of dispersed into the atmosphere. Ive seen people take off the hose to the air cleaner and just put a breather filter on the rocker cover. Don't plug it with a bolt though, as that can cause the pressure to build up in the crankcase, or so I've been told.
Check to see where the other hose runs from the air cleaner. If it runs to a little valve near a heatsheild over the exhaust manifold, its a vacuum valve designed to open a duct so that the hot air from around the exhaust manifold is directed to the intake when the outside air is too cold, like during winter. If thats it, you can disconnect it but it will run rough in winter. If thats not it, I don't know what it is.
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I supported Toymods
Location:
Berowra-Sydney
Registered:
July 2002
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Re: PCV thingo
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Wed, 16 October 2002 00:06
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I had a problem with this pipe as i used to get oil flow through it at high rpm making the car blow smoke, welded up a catch can so it catches the oil but haven't decided if i'm going to run the pipe back into the air intake or just vent it outside the car, as i don't recommend having it venting out into the engine by as those fumes arn't very good and find there way into the cabin when you have the air vents on in the cabin.
thats why i set my vents to recirculate so i don't get the fumes but once it got bumped into the vent position and after 40min of driving on the freeway with the window down as well i started getting a headache and this pain down my back then switched it back over to recirculate and started feeling much better, so either keep it going into the air intake or duct it out away from the car.
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Location:
Adelaide
Registered:
May 2002
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Re: PCV thingo
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Wed, 16 October 2002 06:55
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Hunty: if you van get a hold of a copy fo the Gregorys book for AE82 corollas, it has some diagrams showing where all the hoses and poipe go, where the vales are etc. Quite informative. You can then decide what to yank and what to leave with confidence.
Note that these diagrams were drawn off a 1986 or later AE82 (after the change to unleaded) an my '85 model is quite different.
I have a copy of the book if you want me to phot copy the pages, let me know.
Craig.
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Location:
Adelaide
Registered:
July 2002
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Re: PCV thingo
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Wed, 16 October 2002 08:56
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Craig i've got the gregorys book, just im not too good at reading between the lines. It doesn't say what will happen if i plug this thing up, im pretty sure tho with the amount of air it sucks at idle it would cause serious pressure buildup in the crankcase at high rpm well for a 4ac anyway 
Clarification on the hose, the hose comes off the cam cover and goes into a plug on the flat piece of metal the carby sits on which is then bolted to the inlet manifold is this the throttle body? anyway another hose comes up from down somewhere i cant see, and plugs into a plastic valve thing inside the air cleaner, according to the gregory's manual its a thermosensor. the plastic thing also serves as a vacuum drive for the hot air induction flap on the air cleaner that opens when the engine is cold to allow the hot air from the exhaust headers to be ducted into the air cleaner
There are two hoses coming off the cam cover on my car the PCV and the breather hose when people talk about oil blowing thru it i think they may be gettin confused, the hose im talking about sucks in air not blowing it out. if i let it suck in fresh air ie unplug it from the thermosensor the engine wont idle or run properly. Damn emission control systems, i think i'll just leave it all connected and drill ahole for it in the new chrome cleaner
Thanks for all your help guys
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