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Discussion Starter · #1 ·
I've noticed my 2010 has some oil consumption and a small oil leak coming from the rear main seal. I wondered if I had a pcv issue so I pulled the oil fill cap off while running and noticed there was no suction when I removed the cap. There also appeared to be no resistance when I pulled the oil dip stick out a bit.However, it seems like when people have a PCV failure they have a lot of suction holding these parts in. Is what I have going on normal or is there an issue with something?
 

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PCV bypass will not destroy your engine. Let's look at exactly what's going on here, If the crankcase of an internal combustion engine is completely sealed, it will build up a tremendous pressure inside it. Hot air expands, and a small amount of the high pressure gases inside the combustion chambers leak past the rings and valve seals and into the crankcase. The pressure inside there will always fluctuate wildly as the pistons zoom up and down, but in general the pressure would build and build if the system were completely sealed.
 

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The old-fashioned solution to this was to provide a simple vent. Most commonly, the oil filler cap was vented, and included a simple filter to keep large amounts of oil from leaking out. This would equalize the pressure between the crankcase and the atmosphere. As oil and fuel vapors would build up in the crankcase they would simply escape out the breather and waft away into the atmosphere. It's not necessary to suck the vapor out, you just need to prevent it from forming a "positive" pressure inside the engine.
 

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Those blowby gases cause smog, though. PCV (Positive Crankcase Ventilation) systems were invented to re-route the gases back into the intake system to be burned along with the fuel. Ultimately, the blowby ends up passing through the exhaust and the catalytic converter before they escape into the atmosphere. This cuts down considerably on the amount of unburned hydrocarbons being introduced into the air.
 

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If the PCV system clogs up, though, you have a problem. I've often advised people whose cars are suddenly running poorly that the first thing they should change is their PCV valve. Eventually they become gummed up with grease and the one-way valve "sticks." A positive pressure builds up in the crankcase. That's bad. Crankcase oil is forced past the rings and the valve guides. Spark plugs clog up. Oil consumption increases. Bad things happen
 

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The PCV heater on the TDIs keeps water vapor (which is an ingredient of the blowby gases in the crankcase) from condensing and freezing in the port where the gases enter the intake hose. The stock PCV system is under a constant vacuum, and a vacuum encourages condensation. It sounds like the PCV valve itself is stuck. (Are you sure they didn't just over-fill the engine with oil? That would explain it too.) When I disconnected the PCV I routed the vapor down to the lower pan with 3/4" heater hose. I sincerely doubt that a hose of that diameter could completely freeze up. It's theoretically possible, but I think that's less likely to happen since I had no functional PCV heater in the first place.
 

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Discussion Starter · #7 ·
I recently did an oil change and oil level is correct. I've replaced PCV's on the 2.0tfsi engines so I'm used to a bit of suction when I remove the oil fill cap. So, you're thinking my pcv is either clogged or broken?
 

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LOL your TDI has pcv huh??

Btw if your Touareg is still under warranty, even emissions warranty, they will cover your rear main leak.
 
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