How important is the PCV?
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HT4100 4.1, 4.5, 4.9 Discussion, How important is the PCV? in Cadillac Engine Technical Discussion; I found out that the PCV valve was just jammed into a melted away hose on there.. grrrr I'll fix ...
  1. #1
    FredMaxwell's Avatar
    FredMaxwell is offline Cadillac Owners Enthusiast
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    How important is the PCV?

    I found out that the PCV valve was just jammed into a melted away hose on there.. grrrr

    I'll fix that right away.. the valve itself is good.

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    Re: How important is the PCV?

    It's pretty important... Nothing that will stop your engine or damage it, but it burns up oil vapors and such... Problems with that will affect emissions and mileage a bit.

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    Re: How important is the PCV?

    Correction, the PCV recirculates unburned gas fumes (and oil vapors) into the throttle body. It is one-half of the cause of buildup in the intake manifold and throttle body, the other half being the EGR valve. When the oil vapors turn back into actual oil inside of the intake tract, the exhaust gas sticks to it, causing the nasty performance-hindering clogging.

    Eliminating the PCV valve won't cause any problems, just be sure to cap off the holes. If you run an open tube into the atmosphere, your car will idle at about 1,600rpm. I've got an open vent with a specialized setup so I can adjust my idle speed via controlling engine vaccuum, but a sane person should just cap off the tubes.

    Or pay $5 and get a new PCV valve.

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    Re: How important is the PCV?

    PCV is a good thing. Do not get rid of it, a new valve is like $3.50.

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    ewill3rd is offline Cadillac Technician
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    Re: How important is the PCV?

    Just when I thought I'd heard bad advice before....

    All I can say is FIX IT!
    The purpose of the PCV (positive crankcase ventilation) valve is to remove blowby gasses from the engine.
    When an internal combustion engine runs the compression rings cannot contain 100% of the pressure of combustion. Some of the spent gasses get past the pistons and into the crankcase. Even the retards in the 60's could figure out that the gasses had to go somewhere. They used to use vents that would vent the gasses to atmosphere so they put a valve on the back of the engine with a hose on it to vent the gasses under the car. That is until they started choking and their eyeballs were searing from the smog (with a few other things contributing to the mix)

    The PCV valve uses engine vacuum to draw these gasses out of the crankcase and into the intake air to recycle the gasses back into the combustion process.

    If the PCV valve is removed your engine will turn into an oil sprinkler, every weak seal on the engine... and some of the strong ones will start puking oil, it might even push the dipstick out of the tube and start spraying oil out of that as well. The pressure buildup could also push the rear main seal right out of the block. Moisture buildup inside the engine will turn your oil foamy and leave a nasty residue on everything and the extra hydrocarbons and chemicals that can't get out of the crankcase will quickly break down your oil and probably make it much more corrosive to internal engine parts.

    Fix it, fix it.... and did I mention.... um ... fix it!

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    Re: How important is the PCV?

    Hmm hmm hmm...Yeah I agree, if it were up to me I'd fix it. I've heard about some people trying to modify the system to reduce the carbon buildup. Not sure how that would be done though...at least not without simply collecting the crap somewhere else...

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    Re: How important is the PCV?

    I know the valve doesn't cost too much but it's good any way
    I need to figure out how it was originally on there since some dumbass jammed a hose into the hole on the valvecover instead of putting it right

    I think that I need one of those rubber things with the cut out ring on the edges, it wedges in and pops into place in the hole in the valvecover and then you jam a fitting into that and a hose goes on the fitting

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    Re: How important is the PCV?

    Quote Originally Posted by FredMaxwell
    I know the valve doesn't cost too much but it's good any way
    I need to figure out how it was originally on there since some dumbass jammed a hose into the hole on the valvecover instead of putting it right

    I think that I need one of those rubber things with the cut out ring on the edges, it wedges in and pops into place in the hole in the valvecover and then you jam a fitting into that and a hose goes on the fitting
    Yes, get it el cheapo while you're at the junkyard getting your climate control harness lol. (BTW if that issue isn't resolved in the near future, I'll grab some photos under mine....just haven't had time lately)

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    Re: How important is the PCV?

    "grommet" is the term I think you are looking for.
    Many times you can find the right one in the "help!" section in your local parts store.
    Some applications you can use a piece of 3/8" hose, some you have to get the factory pre-fab plastic pipe.
    Some dealers even carry the PCV pipes if that's what you need.

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    Re: How important is the PCV?

    Quote Originally Posted by ewill3rd
    Just when I thought I'd heard bad advice before....

    All I can say is FIX IT!
    The purpose of the PCV (positive crankcase ventilation) valve is to remove blowby gasses from the engine.
    When an internal combustion engine runs the compression rings cannot contain 100% of the pressure of combustion. Some of the spent gasses get past the pistons and into the crankcase. Even the retards in the 60's could figure out that the gasses had to go somewhere. They used to use vents that would vent the gasses to atmosphere so they put a valve on the back of the engine with a hose on it to vent the gasses under the car. That is until they started choking and their eyeballs were searing from the smog (with a few other things contributing to the mix)

    The PCV valve uses engine vacuum to draw these gasses out of the crankcase and into the intake air to recycle the gasses back into the combustion process.

    If the PCV valve is removed your engine will turn into an oil sprinkler, every weak seal on the engine... and some of the strong ones will start puking oil, it might even push the dipstick out of the tube and start spraying oil out of that as well. The pressure buildup could also push the rear main seal right out of the block. Moisture buildup inside the engine will turn your oil foamy and leave a nasty residue on everything and the extra hydrocarbons and chemicals that can't get out of the crankcase will quickly break down your oil and probably make it much more corrosive to internal engine parts.

    Fix it, fix it.... and did I mention.... um ... fix it!
    "Bad advice"? That's funny considering I said he should fix it, I just happened to also list an alternative - One that works just fine, I might add. I'll let you know when my seals start puking oil or push themselves out. I've run about 6,000 miles without the PCV valve, I guess my engine should be dead by now!

    There's an open vent tube on the 4.9 for the crankcase that runs to the intake plenum, and while it doesn't suck oil directly into my intake manifold and throttle body, it relieves the pressure in the crankcase.

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    Re: How important is the PCV?

    I consider capping it off to be bad advice, I consider putting a tube to atmosphere to vent the gasses bad advice.
    Not only that it is emissions tampering, which as you may or may not have heard is illegal. Particularly if this guy lives in California or any municipality that does emission testing.
    Be offended if you want.

    Maybe this guy is not as talented (no offense to the original poster) as you and doesn't have the time and energy to expend in doing this....
    I've got an open vent with a specialized setup so I can adjust my idle speed via controlling engine vaccuum
    The point is, for a system that costs about 10 dollars to fix I think it's rediculous to offer advice on how to disconnect it.

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    chevelle is offline Cadillac Owners Enthusiast
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    Re: How important is the PCV?

    The PCV system is very important to have working correctly. The PCV system is designed to ACTIVELY clean the crankcase while the engine is running. The system pulls a calibrated amount of clean air thru the crankcase to remove moisture, fuel and other contaminants and byproducts of combustion that would accumulate in the crankcase. This maximizes oil life and engine life.

    A "road draft" tube or simple passive "vent" system as described above is NOT sufficient to keep the crankcase of the engine clean. Ever look at the inside of engines from the era of "road draft tubes" and passive vents and no PCV??? Those are the engines that were sludged and full of crap that started all the old wives tales that persist even today about sludge and deposits and varnish and such. There is a reason for it. The older vent and road draft tube systems did NOT do a good job of cleaning the crank case. Modern PCV systems actively clean the crankcase and do a far superior job. The PCV system is NOT just an "emission control device". It serves that purpose, yes, but it is just as important to the owner as a means of increasing engine life dramatically by actively cleaning the crankcase.

    Any advice to remove, disable, disconnect, plug or alter the PCV system is indeed VERY POOR ADVICE. Don't heed it if you like your engine.

    If any of you followed or heard about the Toyota engine sludging problems you might be interested to know that it was fundamentally because of a poorly designed PCV system. It still worked and did actively clean the crankcase better than an older vent or road draft tube but it was still not sufficient to keep the oil in the engines free of moisture in cold weather. That is how important the PCV system is to the life of your engine. Don't tamper with it and if it is broken or disconnected or plugged FIX it.

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    Re: How important is the PCV?

    Hmm...how easy would it be to make a PCV system in one of those old engines? For some reason, I fear it wouldn't be as simple as drilling a hole in the crankcase and sticking a hose to the intake lol.

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    Re: How important is the PCV?

    Before PCV valves, those of us in very cold climates would find our engines "making oil" as the blowby and raw gas would come by the rings at start and warmup and accumulate in the oil pan. Cars driven on short trips only, would build up as much as a quart a month of crankcase contamination consisting of raw gas, water, and acid. The "road draft" tube did very little until the car warmed up and the car was on the highway to purge this mess. The advent of PCV was a huge leap forward to eliminate this and if there is one feature of your engine that needs to be working to keep the oil clean and free of water and acid it is the PCV system. I can't imagine any sane person wanting to trap this mess in his engine unless he's totally ignorant.

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    chevelle is offline Cadillac Owners Enthusiast
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    Re: How important is the PCV?

    Quote Originally Posted by Tailfin
    Hmm...how easy would it be to make a PCV system in one of those old engines? For some reason, I fear it wouldn't be as simple as drilling a hole in the crankcase and sticking a hose to the intake lol.

    It wouldn't be too hard. It might not be an optimized system but it would be better than nothing.

    Drill a hole in one of the valve covers (assuming it is a V8..??) and use a grommet to mount the PCV valve. Most PCV valves are basically the same inside they just have different outside dimensions so pick one out and drill the hole accordingly.

    Drill a hole in the opposite valve cover and route a hose to fresh air (clean air inside the air cleaner is best). The PCV will pull air thru the engine and regulate the flow via the orifice in the PCV valve and burn the combustion byproducts in the engine as the vacuum pulls it into the intake manifold.

    You might want to put a baffle or some sort inside the valve cover to prevent oil splash onto the PCV valve. This is the area that production systems receive a lot of development to assure adequate oil vapor and oil mist separation before the crankcase fumes are pulled thru the PCV valve.

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