I was just wondering, what are the common steps for diagnosing a PCV? I don't really need to do it, I was just thinking to myself, "Hey, self, I don't really know how to diagnose a PCV!"
I was just wondering, what are the common steps for diagnosing a PCV? I don't really need to do it, I was just thinking to myself, "Hey, self, I don't really know how to diagnose a PCV!"
lots of extra oil leaking out of new places, gas mileage plummets, there have to be a few more
Easiest is to take it out and shake it.
if it doesn't rattle, its broken.
My favorite are the Subaru "non-serviceable" "No its not a PCV" PCV. I dont know how many of those stupid things I have replaced.
Ojala wrote: My favorite are the Subaru "non-serviceable" "No its not a PCV" PCV. I dont know how many of those stupid things I have replaced.
I always wondered where the PCV was. Is that what the unit under the breather on the valve covers is?
Easy way to check. Engine idling. Remove oil fill cap. Place hand over the opening. You should feel vacuum trying to pull your hand in. Or you can use a piece of paper etc. It should stick. If it blows off, the PCV is not working.
The PCV is one of the simplest and most misunderstood systems on the car.
Location of the valve varies with the car.
^ that works great as long as your rings are allowing so much blow-by that it's pushing oil everywhere.
Taiden wrote: I always wondered where the PCV was. Is that what the unit under the breather on the valve covers is?
If you are talking about a Subie then it can be a few different places. Most NA Subies have it on the passenger side just to the left of the throttle body by the TPS. On the turbo 4s its on the block under the left side of the manifold. On the six its down on the driver side by the valve cover.
Ojala wrote:Taiden wrote: I always wondered where the PCV was. Is that what the unit under the breather on the valve covers is?If you are talking about a Subie then it can be a few different places. Most NA Subies have it on the passenger side just to the left of the throttle body by the TPS. On the turbo 4s its on the block under the left side of the manifold. On the six its down on the driver side by the valve cover.
Yeah, on a Subie. I've heard of a few people going to the dealer and being told that they don't have a PCV. I assumed it was like, totally proprietary and weird. I looked it up and it's a screw in type like most PCVs I have run into.
The newer turbo Subies PCV is stuck into a plastic t that attaches to the top left side of the block. So in some sense there is not "just" a PCV because it is molded in with that plastic t.
iceracer wrote: Easy way to check. Engine idling. Remove oil fill cap. Place hand over the opening. You should feel vacuum trying to pull your hand in. Or you can use a piece of paper etc. It should stick. If it blows off, the PCV is not working. The PCV is one of the simplest and most misunderstood systems on the car. Location of the valve varies with the car.
not a valid way to test a pcv.... see way to many new cars that will fail that. nothing wrong no oil consumption.
The proper tool for determining crankcase vacuum is a slack-tube manometer. You'll need the specs on the particular engine to know what you're looking for, but the tool itself is not particularly expensive, and can easily be constructed if you're the DIY type.
02Pilot wrote: The proper tool for determining crankcase vacuum is a slack-tube manometer. You'll need the specs on the particular engine to know what you're looking for, but the tool itself is not particularly expensive, and can easily be constructed if you're the DIY type.
I've never even run into this spec. Is this common? More recent? Is there a way to approximate this spec based on other things? I would love to know more.
Taiden wrote:Ojala wrote:Yeah, on a Subie. I've heard of a few people going to the dealer and being told that they don't have a PCV. I assumed it was like, totally proprietary and weird. I looked it up and it's a screw in type like most PCVs I have run into.Taiden wrote: I always wondered where the PCV was. Is that what the unit under the breather on the valve covers is?If you are talking about a Subie then it can be a few different places. Most NA Subies have it on the passenger side just to the left of the throttle body by the TPS. On the turbo 4s its on the block under the left side of the manifold. On the six its down on the driver side by the valve cover.
On the SVX 6 it's up under the intake manifold. You can remove it without taking the manifold off, but you can't see it without taking the manifold off.
Interesting FYI... The PCV is identical on all Soob's (not sure about Justy??) from the early 80's into the 00's.
Taiden wrote:02Pilot wrote: The proper tool for determining crankcase vacuum is a slack-tube manometer. You'll need the specs on the particular engine to know what you're looking for, but the tool itself is not particularly expensive, and can easily be constructed if you're the DIY type.I've never even run into this spec. Is this common? More recent? Is there a way to approximate this spec based on other things? I would love to know more.
I know from researching the very common CCV failure on BMW M54s that the spec for that engine is 3-6 inches of water measured at idle. I do not know if all manufacturers maintain this spec, or make it available even if they do. I suspect, however, that most modern engines (at least those that route the crankcase gases from the valve cover to the intake manifold rather than somewhere in front of the throttle plate) would not be too far off, given that it is an idle spec.
Bobzilla wrote: ^ that works great as long as your rings are allowing so much blow-by that it's pushing oil everywhere.
That's when it blows your hand off of the oil filler. Or sprays oil onto your safety glasses or that nice white shirt.
KATYB wrote:iceracer wrote: Easy way to check. Engine idling. Remove oil fill cap. Place hand over the opening. You should feel vacuum trying to pull your hand in. Or you can use a piece of paper etc. It should stick. If it blows off, the PCV is not working. The PCV is one of the simplest and most misunderstood systems on the car. Location of the valve varies with the car.not a valid way to test a pcv.... see way to many new cars that will fail that. nothing wrong no oil consumption.
That basically was the way we tested for NYS inspection back in the day. I still have the tester. PCV failure is not directly related to oil comsumption. A line can get plugged or develop a leak along with a faulty valve. As I said above: the PCV system is the most misunderstood things on the engine.
02Pilot wrote: The proper tool for determining crankcase vacuum is a slack-tube manometer. You'll need the specs on the particular engine to know what you're looking for, but the tool itself is not particularly expensive, and can easily be constructed if you're the DIY type.
The tool we used ,as I refered too in my reply to Katy was a simple plastic thing with a ball in it and a green and red scale. the housing had a small hole and a sealing surface. When you placed it over the fill hole, if there was vacuum the ball went into the green, No vacuum it would go into the read. The whole purpose of the PCV system is to create a vacuum in the crankcase and or valve cover to remove condensation and other fumes created there. In stead of blowing it out on the road through the draft tube.
Taiden wrote:02Pilot wrote: The proper tool for determining crankcase vacuum is a slack-tube manometer. You'll need the specs on the particular engine to know what you're looking for, but the tool itself is not particularly expensive, and can easily be constructed if you're the DIY type.I've never even run into this spec. Is this common? More recent? Is there a way to approximate this spec based on other things? I would love to know more.
I doubt there is a spec. There just has to be a vacuum.
On a traditional PCV, there may not be a need for a spec, but on modern systems that include oil separators with drains back to the pan, as well as manifolds to distribute the crankcase fumes to each individual cylinder (with the intended purpose of improving light-throttle fuel efficiency by warming the intake charge), I'd be surprised if there isn't a relevant and meaningful spec. On the BMW M54 (which has all of these features), a common problem after replacing a bad CCV is excessive oil consumption; partially blocked manifolds and drain-back tubes are frequently the cause.
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