PCV Valve Replacement

Is it recommended to replace the PCV valve as preventative maintenance? If so, after how many miles?

I saw it mentioned in a couple of posts when I searched. It came up a few times when addressing issues, but only a couple of times as a routine measure. So, I was curious what the general consensus was on replacement.

 

Bump! Great question. I've wondered this too.

 

As cheap as they are I replace them every 30-50k. its a cheap part and it is a 2 minute job.

 

Great, thanks! Any reason to worry about getting OEM, or is swinging by Autozone to pick one up okay? Also, I understand there is a grommet involved, would it be best to replace that as well?

 

what does it do, and why should it be replaced?

 

i got one they had at autozone. no problems with it. if you can pull the pcv valve out,shake it and it doesnt rattle...it needs replacing.....but you can clean them with seafoam or b12 chemtool and reuse them.

 

pcv is for positive crankcase ventilation...and gets air to the crankcase to help in cooling.(i think anyway..always the way i understood it)

 

I've been looking into this myself this evening, and below is what I found regarding what it is (sounds complicated, but the valve itself is basically a check-valve, I think). When it comes to why should it be replaced, well, I suppose because it can get clogged by deposits?

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"As an engine operates, high-pressure gases are contained within the combustion chamber and prevented from passing into the crankcase (containing the crankshaft and other parts) between the side of the piston and the cylinder bore by piston rings which seal against the cylinder. However, some amount of gas always leaks past the piston rings into the crankcase. This amount is very small in a new or properly rebuilt engine, provided that the piston rings and cylinder walls are correctly "broken in", and increases as the engine wears. Scratches on the cylinder walls or piston rings, such as those caused by foreign objects entering the engine, can cause large amounts of leakage. This leaked gas is known as blow-by because the pressure within the cylinders blows it by the piston rings. If this blow-by gas could not escape then pressure would build up within the crankcase.

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". All the air collected by the air cleaner (and metered by the mass air flow sensor, on a fuel injected engine) goes through the intake manifold. 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 valve is simple, but actually performs a complicated control function. An internal restrictor (generally a cone or ball) is held in "normal" (engine off, zero vacuum) position with a light spring, exposing the full size of the PCV opening to the intake manifold. With the engine running, the tapered end of the cone is drawn towards the opening in the PCV valve, restricting the opening proportionate to the level of engine vacuum vs. spring tension. At idle, the intake manifold vacuum is near maximum. It is at this time the least amount of blow by is actually occurring, so the PCV valve provides the largest amount of (but not complete) restriction. As engine load increases, vacuum on the valve decreases proportionally and blow by increases proportionally. With a lower level of vacuum, the spring returns the cone to the "open" position to allow more air flow. At full throttle, there is nearly zero vacuum. At this point the PCV valve is nearly useless, and most combustion gases escape via the "breather tube" where they are then drawn in to the engine's intake manifold anyway."

 

So what happens if you dont replace it? I have never done the one on my truck, and Ive put about 70K on it, and not sure if it was ever done prior to that.

 

My truck has almost 138k on it and I know for certain it has never been replaced. Again, I'm still in the learning phase here, but I don't think it's a necessary replacement. Like many parts, you can just wait until (if) it fails. If it does fail, it will either stick closed (rare) and blow oil seals, or stick open and allow oil to enter the intake. From what I've gathered by the feedback above, since it's easy and cheap one might as well replace it regularly since a minor restriction can hinder performance, and an all-out failure can lead to bigger issues. Correct me if I'm wrong on this fellas...

 

definitely....with how cheap they are...i'd replace to prevent anything from happening.

 

I guess I can get one tomorrow when I go back for my other belts..

 

since were on the issue. I actually replaced mine yesterday at 135,000. It still rattled, but from the looks of it, it gave me the heebie jeebies from all the crud that was caked on it. So I replaced it for a whopping $3.50.

 

I'm with you man - $3.50 is pretty cheap prevention of future heebie jeebies, or worse...

 

Anyone change it out on the 05+ 4.0?? Was it a PITA?

 

so is it just a generic part then? just any PCV valve will work?

 

You'll need to get a specific one. The one I picked up for my truck works on many Toyotas, and the engine makes a difference too. I think the 4-cyl. and 6-cyl. Tacomas of similar year even use different valves.

There is also a rubber grommet that holds the valve in. I'm not sure if it's necessary, but I picked up a new one of them too.

 

It's recommended to change the PCV every 30k miles or so, you can tell its bad if it rattles when you shake it or if you take the hose off and there is signs of oil then it needs to be changed. If your truck seems to be burning up oil, the PCV is most likely the problem. It's a super easy fix for dirt cheap.

 

might want to try the 2nd Gen section