PCV Valve

You can get it done yourself: fast, right and cheap.

 

I cringe whenever I see those Take 5 oil change commercials. Do you really want someone to try to change your oil in 5 minutes? Not to mention the commercials are really stupid.

 

I misinterpreted this message then; because I can certainly take 5 beers while changing my oil.

 

Thanks everyone for the replies. This forum is a great resource. For the record, I will not be returning to COOL SPRINGS TOYOTA in Franklin, Tennessee.

 

Been a few years since I dealt with them. Sales guy I spoke with back then was alright. Parts team was great. Never did anything with service group there.

I just changed my pcv at 130k. Took 5 minutes and was about $10 from dealer parts counter. It is basically finger tightened in there. Easy to grab with a 22mm socket and extension. (edit: a deep 22mm socket)

 

B-Town aint bullshittin!

 

Would replacing a poorly performing PCV valve result in noticeably increased fuel efficiency?

 

Nope, it is purely a vent for the crankcase. The only noticeable side effect of replacement would be less oil consumption.

 

What this valve does anyways on a natural aspiration engine? Intake manifold always has vacuum, why valve is needed at all? Or is it like the valve closes when intake is throttled (engine braking, idling), because there's no blow-by gases in crankcase, so intake should not suck oil vapors?

 

I just replaced my pcv this weekend when I did an oil change. Tool 5 minutes. Hardest part was working around the foam lol. 6 bucks from Toyota when they were having the 25% off sale.

 

The PCV is a one-way check valve for your crank case. It allows the excess pressure in your crank case to vent to the intake and be re-burned.

The excess pressure is cause by blow-by of the piston, even brand new engines have some sort of blow-by.. These gasses used to just vent to the atmosphere until emissions regulations changed.

The problem is when the PCV gets stuck. Oil will always get through the PCV, just the nature. However, oil "should" cause a pressure differential that causes the vent to close. If stuck open, for example, oil can pass though the valve unhindered. Prolonged oil passage can cause gum up in the intake and on valves and what not. Do

If the PCV is stuck closed, The crankcase could build too much pressure and blow out seals which could then cause oil leaks externally at, for example, the real main seal or front crank seal.

 

Yes. On one side the valve has crankcase positive pressure, on another side it has negative intake manifold pressure. The negative pressure in intake manifold is almost always greater than blowby can ever create, even on an utterly worn engine. There's no way the valve can open based on crankcase pressure alone. So it is perhaps operated by intake vacuum. That's where my question comes in: what does this valve guard? It perhaps allows some crankcase pressure when engine is not under load, in sake of keeping oil vapors away from intake.

 

Ahh! Sorry, I didn't click at first.

Yes, under acceleration, the intake vacuum keeps the PCV open to vent the gasses. Some oil will be pulled through but it should be minimal.

During idle the function is the same but the valve is less open or mostly closed due to low intake vacuum.

Engine brake/decel should close the valve mostly. If stuck open, this scenario would cause the most oil flow through the valve because I believe crank pressure should be higher than intake vacuum.

 

A check valve can be designed to open with very low pressure. Think about a door in your home, very little effort is needed to push it each way. However, once the door contacts the door stop moulding, it is fully closed and isn't swinging the other direction even with great force applied. The PCV valve is very similar, any chance of reverse pressure is eliminated.

 

Thanks! The gasses that are pulled in from the PCV into the intake, do not affect the combustion in any positive or negative way? Or is it just minimal that there are no realized effects?

 

With all the additives in fuel now, you rarely find fuel systems needing cleaned as long as you are buying good gas at a reliable station. I like using stations that are always busy; keeps water out of the storage tank when it is refilled frequently. Still, I put in a bottle of Techron every OCI of 5K just to feel better. I think a lot of the times when they quote the fuel system cleaning, it is really just cleaning the throttle body, which you can do in 15-30 minutes depending on the amount of build up. Only costs you time and about 15 bucks. This usually makes a noticeable difference in throttle response and therefore makes the customer really think they did something and got their money's worth. As for the PCV, don't rely on the shake method to tell if it is working correctly. For the low price and the ease of replacement, it isn't a bad idea to just put on a new one every 50-60k in my opinion.

 

The dealer website on the part listing said replace every 30k. For the price and ease of replacement, I won't argue. Even if it helps get .01 mpg increase, it more than pays for itself.