PCV System - Be aware.

[dcod]

Introduction

Firstly, I'll start by saying that I'm not a mechanic. All information I give is from my own personal experience and from research.

I'm creating this post because I believe the PCV system is an important part of your engine and has the potential to cause irreparable damage if not maintained.


PCV (Positive Crankcase Ventilation) System

A crankcase ventilation system is a way for gases to escape in a controlled manner from the crankcase of an internal combustion engine. A common type of such system is a positive crankcase ventilation (PCV) system, the heart of which is a PCV valve—a variable-restriction valve that can react to changing pressure values and intermittently allow the passage of the gases to their intended destination (which nowadays is the engine's intake stream).

 m http://en.wikipedia.org/wiki/Crankcase_ ... ion_system m


Potential Dangers

1. Excessive Oil Consumption.
2. Sludge Buildup.
3. Engine Wear.
4. Catalyst for Oval Bore/Precat Failure? Unknown.

Approximately 70% of these 'blowby' gases are unburned fuel (HC) that can dilute and contaminate the engine oil, cause corrosion to critical parts and contribute to sludge build up. At higher engine speeds, blowby gases increase crankcase pressure that can cause oil leakage from sealed engine surfaces

 m http://www.autoshop101.com/forms/h63.pdf m

PCV valves are generally considered a maintenance item like spark plugs, and should be inspected and replaced periodically (typically every 50,000 miles). The PCV valve siphons blowby vapors from the crankcase into the intake manifold so the vapors do not escape into the atmosphere. One of the beneficial effects of PCV, besides eliminating blowby emissions, is that it pulls moisture out of the crankcase to extend oil life. Moisture can form acids and sludge which can cause major engine damage. So if the PCV valve or hose plugs up, rapid moisture buildup and oil breakdown can result.

 m http://www.aa1car.com/library/emis2p.htm m

The positive crankcase ventilation or PCV valve is an inexpensive and often overlooked component. It is also one possible cause of expensive oil leaks and sludge buildup in an engine.

The PCV system also helps keep moisture, a major contaminant, out of the oil. When an engine is run, a good deal of heat is generated. As the engine cools, condensation forms. The engine oil absorbs this moisture and attempts to hold it. After a period of time the moisture becomes too much and begins to attack the metal parts of the engine.

Should the engine backfire or if the engine is turbo-charged, the PCV valve can close in the opposite direction if the manifold becomes pressurized. This keeps any positive pressure or fuel vapor from entering the crankcase. Even a very small amount of positive pressure can force oil past gaskets and seals and blow gaskets out of place.

As the PCV valve ages several things can happen. Crud and sludge can cause it to stick in the open position. This might result in a misfire at idle and/or oil consumption. A quality shop can test this using a tool called a manometer.

 m http://www.agcoauto.com/content/plugins ... icleid=197 m


1ZZ/2ZZ PCV System Operation

The purpose of the PCV system is to remove harmful gases from the crankcase before damage occurs and combine them with the engine's normal incoming air/fuel charge. Fuel injected Toyota vehicles use two different types of closed PCV systems to prevent the escape of crankcase vapours into the atmosphere :

1. Fixed Orifice PCV System
2. PCV System Using Variable Flow PCV Valve

The 1ZZ and 2ZZ engines use the latter. More information about how it works can be read in the following (which appears to be written by Toyota):

 m http://www.autoshop101.com/forms/h63.pdf m


Alarm Bells

The first symptom for me, that rang alarm bells, was a ticky engine at full operating temperature (engine sounded fine when cold). The reason for this, I believe, was down to the degredation of the engine oil by the gases being trapped inside the engine. The oil no longer had the correct viscosity at higher temperatures.

After checking the oil level, the second thing I found was 700ml of oil loss in 500ish miles! This sounds excessive consumption but I believe I have an underlying problem of a leaking valve stem seal (the smell of oil upon startup suggests the oil is dripping onto the cylinders when car is not being used and being burnt upon startup) but I digress. I believe the increased pressure forced more oil through this seal.

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Testing and Maintaining

The following is a simple test that can confirm whether the system is operating correctly:

1. Start engine and allow to reach operating temperature.
2. Allow engine to stabalise at idle.
3. Pinch or block hose between PCV valve and vaccum source.
4. Engine should drop around 50 rpm. If engine does not change, check PCV valve and hoses for blockages.

 m http://www.paradiseplace.org.uk/Celica/h63.pdf m

The following link gives a step-by-step guide on getting to the PCV Valve:

 m http://www.diymytoyota.com/corolla/2zz- ... pcv-valve/ m

NOTE: I implore you to check the full system and not just the valve. If the hose is blocked, your valve may as well be just a paperweight. I have also read that many people replace their valves after 30-50k miles. My valve was very black inside due to carbon build up, so I decided to replace mine. (£26 from Toyota UK, $10 in America, welcome to ripoff Britton).

Why did it happen to my car?

My engine has supposedly done 30,000 miles. In my mind, this issue shouldn't have arisen. However, I believe my issue was created by one of the following:

1. Engine was from a cat D. Could the crash have caused this?
2. My engine sat around on a palet for 2-3 months in unknown conditions before being placed into my car.

Now that I have cleaned my valve, my car is no longer using oil (maybe a tiny bit, valve stem seal?). This week, my PCV system is to be checked and cleaned, valve replaced and new oil put in.

Whether I have cured my oil usage problem or not, I believe this post holds valuable information to all. Especially considering checking and maintaining the system is cheap and easy.

Peace   s8) s8)

[K T M Rider]

excellent post  - this is surely worth making into a sticky or How To (as in How To check & maintain your PCV)

[dcod]

excellent post  - this is surely worth making into a sticky or How To (as in How To check & maintain your PCV)

Thank you, much appreciated.

I created this post because I believe it's overlooked (as stated many times in my research). It also refers to ALL cars (not just 1zz and 2zz).

If this post helps just one person fix or increase the longevity of their engine then, to me, it was worth it.   s:D s:D  

Peace   s8) s8)

[Anonymous]

OK old post ressurection but I've just been quoted £96 for this valve by a toyota dealer--- WTF? even he admitted that he couldn't justify that price.....

[dcod]

OK old post ressurection but I've just been quoted £96 for this valve by a toyota dealer--- WTF? even he admitted that he couldn't justify that price.....

That's ridiculous. Get another quote from another Toyota Stealer. Or contact CTP (Cheap Toyota Parts) on here.

MOD - CTP closed shop a while back. Try TCB (in Affiliates) instead.

[andyroo104]

I replaced my PCV valve last week at a cost of £24.46 inclusive of vat from a Toyota dealer,part number is T12204-22051.
Andy.

[Anonymous]

much obliged chaps

I've got the old one out and I'm assuming that it shouldn't rattle?

the sprung  seat / seal is loose as if the spring has gone soft inside - so a new one might help with the high oil consumption I''m hoping

[krazysteve]

usually if it does not rattle it is gummed up, i would say if it rattles it should be ok.
Have you tried to blow through it? only passes air/gases through in one direction.

[ilovejapcrap]

Anyone have pictures of this I'm clutching at straws but could this cause smoke from exhaust

[Ardent]

Picture wise no.
But you will find it under the plastic engine cover, bottom left corner

[Carolyn]

Just 'cos it rattles, doesn't mean it's OK.  If the spring has lost some tension it won't work correctly.  It shows up as a puff of blue smoke when you get back on the throttle.  If it's not sealing at all, it will show up as blue smoke most of the time.

[smarty72]

Anyone have pictures of this I'm clutching at straws but could this cause smoke from exhaust

[ilovejapcrap]

Thanks smarty but I found last night. I'm learning a lot over last few days

[shnazzle]

Changing mine next year + catch can.

[paulj]

Shnazzle, would you recommend changing more than just the valve?  I have just bought a new valve to change and now wonder if the catch can and anything else needs doing.  Also, where is the can - the hose disappears down the back of the engine and I suppose I will need extending fingers!

Thanks

[shnazzle]

Shnazzle, would you recommend changing more than just the valve?  I have just bought a new valve to change and now wonder if the catch can and anything else needs doing.  Also, where is the can - the hose disappears down the back of the engine and I suppose I will need extending fingers!

Thanks

There is no catch can  s:) s:)  That's the problem. The gasses go straight from the rocker cover to the intake. So, possibly mucky oily air is going into the intake.
It would be an added "mod" from me.

It's not really that necessary on a naturally aspirated car as the blow-by gasses are less likely to contain so much oil. But I thought (and our trusted Steve@D1 agreed) that it certainly can only be a good idea.
As for Helen's car (turbo) there's a higher chance of oil being forced up through. So hers definitely needs it

[ChrisGB]

And too much oil mist in the inlet can lead to knock.

[paulj]

Thanks shnazzle, wanted to check as I thought catch cans went out with emissions changes.  The only one I saw was on an old 1960s rover engine and was simply the equivalent of a tube into a baked bean tin.  Also get the additional concern for turbos.

[shnazzle]

Thanks shnazzle, wanted to check as I thought catch cans went out with emissions changes.  The only one I saw was on an old 1960s rover engine and was simply the equivalent of a tube into a baked bean tin.  Also get the additional concern for turbos.

I'm not sure how the 1zz rocker cover is made but the VAG turbo engines have a pretty convoluted path in the cover for the gasses to pass for it to drop as much oil as possible.
That's probably common across all modern engines. Hence not much need for catch cans.
Having said that... EGR valves do as much or more damage if you ask me...

But anyway, I pulled the hose off my pcv a while back and there was a tiiiiny layer of oil so.. I'd rather have no oil at all than a tiny bit.

There are catch cans and catch cans. The ebay empty cans are about 20% useful (made up statistic) but a proper baffled one (100-odd quid) are good

[Carolyn]

The (rocker) cam cover does indeed have a tortuous path.  On a standard 1ZZ there is nothing wrong with the oem set-up.

[Myles1ZZ]

Is this the correct part: http://www.ebay.co.uk/itm/Genuine-Toyota-PCV-Valve-Avensis-2002-1220422050-/222147351185?fits=Model%3AMR+2%7CPlat_Gen%3AMK+III&hash=item33b9039291:g:VxYAAOSwnNBXWWaj ?

Thought I might as well replace mine just to be sure. The description in the link says it only fits 2004/2005 models? That can't be right can it?

[Carolyn]

Myles, the PCVs on the 1ZZ FE are all the same.

Here's a pic of the inside of the cam cover.

[MrT]

Great help, thanks dcod.

Would this cause poor emissions do you think? I dont believe I have high oil usage but then my car has been off the road and failed it's road test for high emissions.

Thanks

[Carolyn]

It's possible but more likely a duff cat (especially if there's no obvious blue smoke).  Put your emissions result in a post and then we can see.... or could be your MAF  not doing its job properly (MAF doesn't throw a code).

[MrT]

Hi Carolyn.
Already posted and had no replies... But thanks, I'll investigate. I don't believe it is the mad as I tried a new one already. Might be cat, its very large bore, I assume performance cat. Emissions weren't far out. I'll post the results.