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Mysterious Oil Consumption? Change your PCV Valve!


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52 replies to this topic

#1 ccrinc

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Posted 13 June 2008 - 02:22 PM

For the lack of a $15 part, engines are lost.

I may be preaching to the choir, but I get so many calls from people who now need an engine because some idiot mechanic couldn't figure out that a car using excessive oil probably just needs a new PCV valve. Especially if there are no leaks!

People who have already spent over $1000 for needless head gasket replacements, valve adjusts, oil pumps, etc. The only symptom? Using an unusual amount of oil.

It's not electronic, so a code reader isn't going to show a problem. Oh, and that slight knocking sound that this mechanic is going to fix with a valve adjust? The beginnings of a rod knock folks! From running the oil low repeatedly.

(Yesterdays call: "But, it was only 2 quarts low!" In an Impreza! :banghead: )

Are we in the business of selling engines? Yes. But we feel bad when the customer tells us how much they've already spent with some idiot, unscrupulous mechanic who could've saved the engine by putting in a Subaru Genuine PCV valve. GAWD!! :mad:

(Sorry for the semi-rant. I've told many potential customers that, as much as I'd like to sell them an engine, replace your PCV valve first. Guess what? I never hear from them again!)

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#2 CNY_Dave

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Posted 13 June 2008 - 02:39 PM

Is this from the PCV valve getting stuck open, or shut?

Dave

#3 OB99W

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Posted 13 June 2008 - 02:57 PM

If the PCV valve is stuck closed (or hoses are obstructed), blowby pressurizes the crankcase and can force oil past seals. If the valve is stuck open, the engine can consume (burn) more oil than it normally would, via the intake.

#4 hohieu

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Posted 13 June 2008 - 03:09 PM

If it's stuck closed or clogged, oil can also be forced into the breather tube attached to the air filter box, which can also wreak havoc on any sensors downstream from this vent.

#5 gbhrps

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Posted 13 June 2008 - 07:04 PM

My 90 Nissan 300ZX toy started leaking from its rear main seal some 10 years ago, marking its territory on my garage floor after each run. The repair estimates were into the $1000 range to pull the exhaust, drop the clutch and tranny and replace the seal. Someone who had been there and done that suggested replacing the pcv's first (car has two of them). $30 later I had no oil leak and it hasn't reappeared since.

#6 Suzam

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Posted 13 June 2008 - 07:21 PM

This is good to know, next time I'm in the parts department I'll pick up one for each of my Subies.


"An ounce of prevention....."

#7 OB99W

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Posted 13 June 2008 - 07:42 PM

I should also mention that a PCV valve stuck open often causes poor idle quality.

#8 bulwnkl

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Posted 14 June 2008 - 09:06 AM

Note to all late-model turbo owners:

Do not just buy the PCV valve from Subaru. Buy the whole plastic assembly it's in. The valve alone is almost impossible to remove from the assembly, and the assembly is often cheaper from the dealer than the valve alone. Plus, arm yourself with some hose clamps since the ones used in that area are designed as one-time-use and may or may not be able to be re-used (though I was successful when I did it about 3 weeks ago).

#9 subaruplatt

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Posted 15 June 2008 - 09:35 AM

I used to let some gasline antifreeze get sucked into the PCV system on my old VW. With a puff of smoke out from the tail pipe all isv problems got solved.
:grin:
This was a very cheap fix at 99ยข each for a couple of little bottles.

And this problem was masquerading as electrical as the furry crud would tend to swell on wet days.

#10 tucson_legacy

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Posted 15 June 2008 - 10:02 AM

I removed my OE PVC valve (EJ22 NA) and it had a little sludge in it. (it still rattled, however) I washed it out with brake cleaner and re-installed it.

Is it really necessary to replace a PVC valve if one can clean it instead?

What would be the advantage of replacement?

#11 OB99W

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Posted 15 June 2008 - 05:36 PM

Is it really necessary to replace a PVC valve if one can clean it instead?

If you can clean it to the point of the plunger moving freely and properly sealing as required, that's almost all that's needed. The remaining consideration is whether the spring has fatigued through usage, and if the valve therefore still operates as when new (although that doesn't seem to be a common problem).


What would be the advantage of replacement?

Beside the spring fatigue issue, mainly the advantage is in profit to those selling PCV valves. :)

#12 Andyjo

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Posted 16 June 2008 - 08:49 PM

I bet that's where my oil has been going..... silly 2.5T.... and I thought it was because I beat the snot out of it :-p

#13 95LEGOBW

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Posted 16 June 2008 - 11:25 PM

This is good advice. I have had the same experience on other engines - smoke, oil in the airbox, black spark plugs, all of which went away when the plugged PCV was replaced with new.

On my Subaru, is the PCV the metal device screwed into the intake manifold, just to the left and toward the firewall side of the distributor (on a '95 2.2)?

If so, mine was mostly plugged and didn't seal well. I cleaned it up with brake cleaner and a little bit of scraping. It will now click when I moved it back and forth in my hand, and the spring has behaves just like in new ones.

After the cleaning, I could easily blow through the PCV in one direction, and just barely blow through it in the other. Since it threads into the manifold on just one end, there was no risk of installing it backwards.

I also found that the pipe connecting to it was partially closed by accumulated crud, as was the T-connector just below it. The crud was pretty crusty, and broke down and came out easily. The car has 180K on it, and doesn't get driven a lot, so that's probably been contributing.

I have had a slow oil leak for about a year - the bottom of the engine always has a film fo oil on it, but there are no drips in the garage & the oil level doesn't drop measurably between oil changes. I don't know if freeing up the PCV has helped this, though. Have to wait and see.

#14 OB99W

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Posted 17 June 2008 - 05:56 AM

[...] On my Subaru, is the PCV the metal device screwed into the intake manifold, just to the left and toward the firewall side of the distributor (on a '95 2.2)? [...]

Yes, if by "left" you mean while facing the engine from the front of the car, and by "distributor", you're referring to the ignition coil pack.

The following link should help for many normally aspirated (non-turbo) models:
http://www.northursa...in/pcv/pcv.html

#15 SubPar

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Posted 17 June 2008 - 10:02 AM

Wait, wait. The idea I'm getting from this thread is routine maintenance could save money and heartache in the long run? Strange concept. I'm just going to keep running my car only two quarts low, and see what happens.;)

#16 CNY_Dave

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Posted 17 June 2008 - 12:21 PM

Yes, if by "left" you mean while facing the engine from the front of the car, and by "distributor", you're referring to the ignition coil pack.

The following link should help for many normally aspirated (non-turbo) models:
http://www.northursa...in/pcv/pcv.html


Wish the 3.0 PCV valve was that easy to get to...


Dave

#17 OB99W

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Posted 17 June 2008 - 03:43 PM

Wish the 3.0 PCV valve was that easy to get to...

Which is why, unfortunately, I had to say "many" and not "all".

#18 OB99W

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Posted 17 June 2008 - 03:45 PM

[...] I'm just going to keep running my car only two quarts low, and see what happens.;)

Do keep us posted on how that works out for you. ;) :)

#19 Nutella

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Posted 25 July 2013 - 10:29 PM

Can a car blow through 3 quarts of oil in 2000 miles with a bad PCV Valve?

 

Are there going to be any ramifications of driving with low oil? 

 

I just got the car and only had driven it 2000 miles when the oil light came on. I immediately put 3 quarts in (before it would show on the dip stick)

 


#20 Fairtax4me

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Posted 25 July 2013 - 11:03 PM

If the pressure light came on, yes, ramifications. Maybe not right away but there was bearing damage done by running that low on oil.

Yes, a stuck PCV valve can allow several quarts of oil to burn away in only a few thousand miles, especially doing a lot of highway driving, where high rpms (3000 or more) are sustained for extended periods of time. Most Subarus tend to use about 1/2 quart or a little more in the 3,000 miles between oil changes anyway.

#21 ThosL

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Posted 26 July 2013 - 08:53 AM

Ok, thanks for the warning.  I will try to check mine today.



#22 AWDFTW

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Posted 26 July 2013 - 10:41 AM

+1.  Every time I have experienced sudden increased consumption in a Subaru, it has been a failed PCV.

 

On our old 96 Outback, it went from the normal "up to a quart" over a 3-5k OCI to "Wow, I just put over 3 quarts into my 4.5 quart sump after a 600 mile roadtrip".  New PCV, back to normal.

 

On our current 2003 Outback, it stays in the "about a half quart" over a 5-7k OCI.  PCv clogged and it jumped to 1.5 quarts in 5k.

 

Cheap and easy fix.  I have had poor luck with auto part stores PCV, so I stick with ordering an actual Subaru part.  Still, under $15 for something that lasts around 100k in my experience.



#23 ThosL

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Posted 27 July 2013 - 03:37 PM

I changed mine yesterday, it took fifteen minutes which will probably cause the mechanics to laugh, but hey, I used a dysfunctional wrench.  The old one did look clogged up a little, too bad it is not automatic to offer a replacement when they are changing the oil.  There is no lube needed on 99 outbacks only oil and filter so what's the big deal?  Why do they need to exagerate the mystique of mechanic work by charging so much?  My sister is paying $50 per oil change, and she hardly drives her Subaru while I have nearly 245K on mine.



#24 spartus4

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Posted 18 March 2014 - 10:51 AM

Just managed to find my PCV valve yesterday and removed the hose that went to it and oil just flowed and flowed out.  Managed to get the valve out after removing brackets and wiring out of the way.  The darn thing was so clogged that there was no sound what so ever when it was shaken.  I have been having problems with rough idle and the trans shifting hard.  Some oil (but not much) has been on the garage floor.  Cleaned the valve out with some spray starter fluid that I had laying around and now it idles perfect, no more oil on floor and tranny shifts much better.  It's amazing how such a simple part can cause so much trouble yet be so easy to change.  I don't understand why they don't change it at the dealer with regular service, seems like a no brainer.



#25 robm

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Posted 18 March 2014 - 12:07 PM

This topic should be in the USRM.






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