I've come up with the very best way to bypass your PCV system. Thoughts on my idea?
Posted by Blu_yello_husky@reddit | askcarguys | View on Reddit | 26 comments
It should be noted that you shouldn't do this if your engine is in good condition and functioning properly. My reasoning for doing this is because I have a dead cylinder creating excessive blow-by, causing my PCV valve to stick open and effectively creating a large vacuum leak, which prevents the engine from idling and dies when not moving.
So, how to draw out crankcase vapors without using engine vacuum? Well, we've all heard of road draft tubes, right? The issue with the draft tube, is it allows foreign material and moisture to backtrack up the tube and end up contaminating the oil. The solution? Run a 5/8 inch transmission/brake fluid line from the PCV valve hole on the valve cover, to the downstream O2 sensor hole, where you have installed a threaded coupler in its place. Flare the line and use a flare-nut to connect the coupler to the line coming from the valve cover. Install a one-way check valve in the line somewhere to prevent exhaust gases from backflowing into the crankcase.
Now, what will happen, is the flow of exhaust will cause a siphon effect to the line going to the valve cover, drawing out crankcase vapors and sending them right out the tail pipe. No worry of water or contaminates getting into the valve cover from outside, and no need to worry about running lean from a stuck PCV.
It won't be as efficient as a PCV system, but it will at least make your car drivable again. The only time this won't work is if you live an inspection state, in which you will now fail emissions testing because of raw oil being burnt up in the exhaust, but such is life. It's better than spending thousands on an engine overhaul when the car still runs fine.
CraziFuzzy@reddit
At this point, just disconnect it and let it blow on the ground.
Blu_yello_husky@reddit (OP)
Then water and road debris has the potential of getting up into the pipe and back into the engine. If you send it to the exhaust, the system is sealed, no contaminates are getting through
CraziFuzzy@reddit
With high crank case pressure, that's just not going to happen. It'll be blowing out the whole time.
Lerch98@reddit
Need a check valve.
Blu_yello_husky@reddit (OP)
Re read the 2nd paragraph, it's in the instructions
Gunk_Olgidar@reddit
Welcome back to the 1970s when we put filter-breathers on our valve covers because rings didn't last much past 100kmi and cylinders were not nearly as tight as they are today. Oil was conventional dino juice, gas was dirty and full of sulfur and lead, gaskets were made of cork, and crank seals made of hemp. Good times. If it leaks oil, then it still got oil in it.
If this same amount of effort was made for regular maintenance and repair, all the breather plumbing shenanigans would not be necessary. Concerns about moisture and contaminate intrusion are moot when you have a dead hole already wrecking everything inside the engine and blowing everything else out.
I suggest, for improved credibility, that you actually test your idea before you go selling it to the public via reddit, FB or otherwise. So go chagne your oil and run 3k miles stock with a working PCV, change the oil a 2nd time and send a sample to a lab for analysis. Then do your PCV mod and run it for 3k, change oil a 3rd time and get another analysis. Compare your two data points. Report back here.
Blu_yello_husky@reddit (OP)
I've had this hooked up for a week now on my own car, it's been working great so far. I can actually drive my shit again.
Can't, it won't run with the PCV hooked up, that's the whole issue.
ThirdSunRising@reddit
What an enormous undertaking for something that has a very simple solution. Besides an engine rebuild, I mean.
Just plug the vacuum port and route that crankcase vent into your air cleaner and let those fumes go into the intake. It's no longer a vacuum leak but the fumes still go to their original intended destination, to be burned off quickly and easily. And you didn't have to disconnect your O2 sensor or make any other unwanted "modifications," you just plug the vacuum port and route the blowby hose into your air cleaner, downstream of the filter. Duh.
Blu_yello_husky@reddit (OP)
Then it gets oil all over the air filter, that's an even bigger problem.
There is no downstream of the air filter, there's only the port on the bottom of the throttle body where the pcv hose was connected to begin with.
Yeah, exactly, and that's the issue. A PCV is just a controlled vacuum leak. If it's stuck open, it's just an uncontrolled vacuum leak, which will cause a no idle condition. Any amount of air coming into the intake outside of the primary or secondary intake holes is a vacuum leak, which will cause the engine to go lean and die. What you described here is how it was originally routed to begin with, which doesn't work. The crankcase vapors need to be drawn outside of the engine, not back into it
SkylineFTW97@reddit
Dude, yout engine has one foot in the grave. The dead cylinder is way more of a deal breaker than PCV problems and you ignored that. Either leave it br and send it or put it out to pasture. Nothing else makes sense given your situation. Save your time and effort for a car that doesn't have a bad cylinder in the engine.
blizzard7788@reddit
You could just run the hose straight done and vent to atmosphere. I removed the PCV valve on my boosted 4.6 Mustang. Both valve covers go to catch cans and oil fill cap has a filter vent.
Blu_yello_husky@reddit (OP)
That opens up the possibility of moisture backtracking it's way up into the PCV hole. It needs to be a sealed system to prevent that, otherwise I'll have to change oil alot more often
blizzard7788@reddit
Not necessarily. The passenger side valve cover had a hose that went to throttle body that was always open to atmosphere. As long as oil gets to operating temp. Moisture would be burned off. It’s a moot point anyway. It’s a boosted track car on E85. Oil gets changed every other month.
Blu_yello_husky@reddit (OP)
I was referring to my own application, I don't want moisture in my engine
Which_Initiative_882@reddit
Youve already got moisture in there... every engine does. Thats why its so critical to always get the engine fully warm every time you run it. A VTA crank vent system isint going to let enough moisture in to be a problem, fuel dilution however is your larger concern here.
HotmailsInYourArea@reddit
You already have a dead cylinder and excessive blow-by, a bit of moisture is the least of your worries haha. You should already be changing the oil more frequently and you should definitely have the fuel shut off to that bad cylinder.
Blu_yello_husky@reddit (OP)
Can't shut off fuel flow on a carbureted engine
HotmailsInYourArea@reddit
That does make it harder!
ride5k@reddit
it's not the very best way.
Jmorenomotors@reddit
What you're describing already exists, and it's been used in the motorsports world for years.
I would suggest you switch your pcv valve to a fixed orifice. GM did this with the Vortec engines in the early-mid 2000s (look up a pcv valve for 2004 Suburban). Instead of having the check valve type, they just use an empty valve that has a small approx 1/8" hole, so it allows just enough flow to serve the purpose but it's not a big gaping vacuum leak. Other companies have done this as well, like Jeep with the 4.0, where they use a permanent fixed orifice in the valve cover.
d00kieshoes@reddit
Seems like a fools errand to me. I'd either fix the engine or move on and buy something else.
Blu_yello_husky@reddit (OP)
Not worth fixing the engine, and the car has lots of life left in it otherwise. I also like the car, and I refuse to drive anything else until this one is absolutely undriveable
the_one-and_only-nan@reddit
The real fix here is replacing your engine that has a dead cylinder with one that doesn't. PCV valves are nothing but check valves that allow pressure to escape the crankcase, but will close if the crankcase is under vacuum. A lot of euro cars keep the entire crankcase under manifold vacuum, but most other cars will have an unregulated breather for the PCV system into the valve cover so such so that air is constantly flowing through the crankcase.
If you put a new PCV valve in, capped off the vacuum line on the manifold, and vented the valve to atmosphere you'll be able to drive it fine until the valve plugs up. You could try running a type of catch can on the PCV line to help filter any shit that leaves the crankcase
Blu_yello_husky@reddit (OP)
Not everyone has the means/money/desire to do that. In my case it's all 3. The car isn't worth a new engine, it's quite old and rusty, I'd be putting a new engine into a car that is literally going to fall apart in the next 2-3 years. I'm going to drive it until it's absolutely undriveable, whether it be because the suspension went through the trunk floor or the interior just disintegrates entirely from sun and water damage.
Doing this will result in oil all over under the hood, which I don't want. I already had an engine fire a few years ago in this car, I'm not dealing with that again. It's no fun. Just venting without any suction also won't get rid of moisture caused by short trips and condensation inside the engine on hot days. Having the exhaust suck it out will be more efficient and make the engine last longer
No_Pension_5065@reddit
This will kill your cat
Blu_yello_husky@reddit (OP)
That's why I said downstream sensor hole