# Burning Smell, Oil Film on engine during very cold weather (both W12 and V8)



## conmoto (Jul 8, 2009)

I drove about 300 miles this evening from Madison, WI to Saint Paul, MN. All interstate miles, normal driving. As I neared my house in the city, I switched to manual shifting to engine break for a stop light. It's cold here. About 2 degrees Fahrenheit. The engine temp was about 170, so out of curiosity, I wanted to see if I could raise the engine temp by staying in a low gear from one stop light to another. I stayed in 2nd gear and revved no higher than 4000 rpm for about 30 seconds. Sure enough, the temp went up a tiny bit, but I detected what seemed like a burnt rubber smell. I wasn't worried, I thought it was someone else. I got home and still detected a smell, so I opened the hood to find a light splattering of oil on both sides of the engine. I assume it is engine oil, but I'm not 100% sure. I restarted the car and let it idle. No warning lights or spewing liquid from the engine compartment. Any ideas what happened?


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## conmoto (Jul 8, 2009)

http://www.flickr.com/photos/[email protected]/11396735496/


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## Gabs08PHTN (Jan 6, 2011)

Hi,
It is quite odd that the oil spewed towards the engine covers... That makes me think that it could come from the front of the car, and that the oil was pushed by the air entering into the engine bay through the radiator. The only oil related pipes at the front of the car are the steering fluid cooler lines that sit in front of the radiator, behid the front bumper.
If you have a look at the upper noise insulation that is attached at the hood and see some more oil spews, that might give you some insight too. Other than that, check the steering and engine oil levels. Also, inspect the engine bay with a good torch.
Additionaly, in case you do no find the origin of the oil spew, tidy up the engine bay and look for further oil spewing.
I hope it helps.

Gabriel


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## conmoto (Jul 8, 2009)

*Puzzled and Worried*

I drove the car this morning. Reached full operations temperature applied brakes with force, turned the steering wheel often, and reached 4000rpm a couple times. No new oil. Weird.


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## jyoung8607 (Feb 14, 2006)

Very puzzling. I was going to suggest cam seals as something that can sometimes drip and create a burning smell on this generation V8/V6. But seeing your picture, I can't correlate that spray pattern with anything except perhaps the valve covers, and that would have to be quite severe.

In your pictures it appears that the air filter boxes have been sprayed with stuff on the far side of the thermal insulation (the silver sheet) away from the engine. It's possible something came up from underneath. Is there anything splashed on the underside of the hood? Are you sure the noise insulation panels underneath your engine are still present? On other VWs it's not unknown for those to get ripped off by debris or by deep snow and ice. The Phaeton's panels are pretty solidly bolted on but it's worth checking to see if something could have splashed up from underneath.

FYI, your air filters are probably clogged up. There's a dial on top of each airbox that measures the highest intake vacuum it's seen. Both of yours are maxed out in the red. You should open those up and inspect/replace your air filters along with the snow screens in the bottom. The snow screens tend to clog up easily, well before your paper filter elements. Or, I suppose for the first time in living memory they actually might have done their job and blocked out powdery snow from the intake. I actually have them removed from my car but mine doesn't see nearly as much snow as yours probably does.

Jason


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## invisiblewave (Sep 22, 2008)

Jason, should those filter dials reset by either turning them or taking off the top of the airbox? I have one that appears to be stuck. I checked the filter and cleaned the snow filter, but it won't budge from red, when I turn the knob it immediately spins back under spring pressure to red.


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## jyoung8607 (Feb 14, 2006)

invisiblewave said:


> Jason, should those filter dials reset by either turning them or taking off the top of the airbox? I have one that appears to be stuck. I checked the filter and cleaned the snow filter, but it won't budge from red, when I turn the knob it immediately spins back under spring pressure to red.


From what you say, I think it's defective. If memory serves, they were one-way ratchet mechanisms. They can be reversed by hand, but will only advance under vacuum. I think there may have been 3 or 4 "steps" between full white and full red? Not sure. Anyway, you should be able to reset them from the knob on the top without any dis-assembly. If yours snaps back to red immediately it probably needs to be replaced.

I've only had to do mine once around 35k miles, not long after I bought it. The snow screens were loaded up with debris. They haven't budged since and I'm up to 72k miles, with the filter elements replaced at 40k according to the maintenance schedule.

Jason


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## PanEuropean (Nov 3, 2001)

conmoto said:


> I got home and still detected a smell, so I opened the hood to find a light splattering of oil on both sides of the engine. I assume it is engine oil, but I'm not 100% sure. I restarted the car and let it idle. No warning lights or spewing liquid from the engine compartment.


Hi Conmoto:

I am going to GUESS that the problem has something to do with water vapour in the PCV (Positive Crankcase Ventilation) system freezing up, and one of the small hoses in the PCV system coming off of whatever it is supposed to be attached to.

I say this because I have just had a similar experience, on a somewhat larger scale: I just drove my 2004 W12 across Canada - from Vancouver Island to Toronto, a distance of about 4,500 km - in extremely cold temperatures, the average daily temperature being -25°C (about -15°F). Halfway through the trip, I began to smell an unwanted burning smell from the engine area whenever I stopped at a gas station to fill up. I also noticed that the top of the engine was coated in a film of oil, but that the oil quantity (as measured by the dipstick) had not decreased.

I'm going to take the car into the dealership this week and investigate - I'll report back and let you know what I have found.

Michael

*PS:* Sorry to have been absent without notice from the forum for so long, but I have been working non-stop since about August, and only home in Canada for 5 days since then. I permanently solved that problem by retiring.  So, give me a week or so to settle into retirement, and I will become active here again.


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## MN Flats (Nov 24, 2011)

Hey Michael, what did you find out, if anything?

I had a similar episode last week, only I think it was worse than what you guys are describing. I was cummuting home in about 5F temps when after I got off the highway and waited at a traffic light I smelled something burning. I thought (and hoped) it must be the guy in front of me, so just drove home - only 1 mile further. As I pulled into the drive, I saw smoke coming out from under the hood. Once in the garage, it continued to billow up and fill the garage. It was so bad I thought it might burst into flames. It had a weird plastic smell as I recall, but it could have been oil. I opened up and saw the smoke coming up around the drivers side of the engine, almost by the left wheel. 

The only sign of trouble before this was the "Level Fault Workshop" came on about 2 miles before I got off the highway. Could it have been the compressor burning up? I ran the codes two days later and got nothing. The rear suspension had dropped way down. Started it up, got no warnings on the screen. Drove around the block and everything seemed OK, but pulling back into the driveway the "Level Fault" came back on. I am hesitant to even drive it to the shop (15 miles).


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## PanEuropean (Nov 3, 2001)

Hi Dan:

I never was able to reach any definitive conclusion. I originally assumed that crankcase vapour that should have stayed within the PCV (positive crankcase ventilation) system was escaping through the two large gaskets that hold the throttle body assemblies on either side of the W12 engine. So, I ordered two replacement gaskets (they are hellaciously expensive, about $150 each), but while waiting for the gaskets to arrive from Germany, the problem went away and never came back.

I've now been driving the car for about 8 weeks, some of that in extremely cold temperatures (-10°C to -20°C, same conditions as I originally had the problem in), but the problem has not returned.

So, I can only speculate that during very cold temperatures, if someone makes a very long drive - in other words, the engine is running for 3 or 4 hours continuously - vapours freeze in PCV lines somewhere, and the result is that oily vapours get forced out into the engine compartment. Where they escape from I have no idea - I could never find the source of the leak.

I also speculate that when we only use the car for short periods of time (i.e. less than 2 hours continuous duty), perhaps not enough vapour accumulates and freezes, hence no problem appears.

For what it's worth, during my cross-country trip (when I encountered this burning smell), I was leaving the car outside overnight in hotel parking lots, with OATs of perhaps -25°C overnight. Now that I am home in Toronto, the car gets kept in a warm garage every night. It is possible that liquids might have been accumulating and freezing during the time the car was outside continually, but now that it is inside every night, any accumulation of frozen vapour has lots of time to thaw out every night. So, whatever caused the problem is not getting a chance to accumulate in a frozen state from day to day. Again - all this is speculation on my part.

Michael


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## conmoto (Jul 8, 2009)

*Puzzled and Worried*

I've also had no reoccurrence of the oil splatter/smell issue. I'm due for an oil change soon. I'll have the mechanic take a closer look to search for the source.


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## PanEuropean (Nov 3, 2001)

Hi Brad:

Let me know if your mechanic finds anything. My mechanic - a real Phaeton wizard - looked really, really carefully at my car, and could not find any form of leak anywhere - but, the top part of the engine (where the spark plugs are) was kind of coated with a light film of oil, which is something I have never seen before.

So, for sure, some kind of liquid or vapour (most likely oil vapour) was escaping from the engine area, and it was burning on hot parts (probably the exhaust parts that are attached to the engine), and it was making a heck of a stink when I stopped the car after driving it for a long time. But... that problem only happened under the following circumstances:

1) Car was parked outside overnight in very cold weather (night-time lows below -25°C), thus it was totally cold-soaked when I started it.

2) I drove for a long time (>1 hour) in equally cold weather.

The problem has not returned in the past 8 weeks, probably because I have been keeping the car inside a warm garage when I am not using it.

My guess is that some kind of crankcase ventilation valve froze up.

Michael


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## MN Flats (Nov 24, 2011)

Hi Michael, 

Thanks for the information. Here is an update on my case: Took it to the shop and they are saying 1) the crankcase breather valves (same as PCVs right?) are clogged and 2) the valve cover gaskets are leaking copious amounts of oil onto the exhaut manifold. $2200. 

It would make sense that if the PCV system plugs, the pressure is going to push oil out somewhere, but I'm not convinced the gaskets are shot, so I'm going to drive it for a while and see what leaks. On the drive over to the shop (20 miles), no smoke. 

Is it common for gaskets on a W12 to go out at 80K miles?

Do you think the valves need to be replaced? Is that common?

Cheers,
Dan


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## jyoung8607 (Feb 14, 2006)

MN Flats said:


> Hi Michael,
> 
> Thanks for the information. Here is an update on my case: Took it to the shop and they are saying 1) the crankcase breather valves (same as PCVs right?) are clogged and 2) the valve cover gaskets are leaking copious amounts of oil onto the exhaut manifold. $2200.
> 
> ...


I can't recall W12 valve cover gaskets being a common complaint here. They are nice gaskets and the fastener design won't let you put too much pressure on them, so they should stay sealed and pliable under varying conditions. As you say above though, if the PCV system is plugged, the pressure is going to go somewhere and the VCG will probably be the failure point. Depending on where the leak was, the gasket _might_ still do its job after pressure is reduced. Far from certain though.

Jason


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## PanEuropean (Nov 3, 2001)

Hi Dan:

Well...

It can be tough on the technicians when we bring a car in with an uncommon problem and we want the problem fixed. The tech, by nature, wants to kill the problem dead the first time around (this to avoid customer dissatisfaction arising from recall visits, etc.), and the pressure to solve the problem completely on the first visit can sometimes result in more work being done than might be necessary.

On the other hand, here in the forum, we owners can kick an uncommon problem around, research it for weeks, benefit from the different perspectives each of us brings to the problem, and even enjoy ourselves as we work towards a solution. For us, the fun is finding the root cause, then identifying the 'silver bullet' that prevents the problem from recurring.

I think it is a very credible hypothesis on the part of your tech that the PCV valve (or valves - I have no idea how many there are, or where they are) became plugged, and this resulted in crankcase gases containing an oil mist escaping into the engine compartment. That is more or less the same hypothesis that I put forward in post #8 above. But, the unanswered questions (so far) are these: WHAT is causing the PCV valve(s) to become plugged, and why is this problem with oil mist in the engine compartment only being noticed during exceptionally cold weather?

At this point in time, I am guessing that water vapour is freezing up somewhere in the PCV system (perhaps in the PCV valve(s), or perhaps somewhere else in the PCV plumbing), and this is forcing the oily crankcase gases to escape into the engine compartment. How and where these gases are escaping I have no idea. What we do know is that this problem only occurs when it is very cold outside... but we're not yet sure if it is a result of parking the car outside and letting it get cold-soaked, then operating it, or simply operating the car during very cold temperatures (even if the car had been stored indoors prior to operation).

I "kinda-sorta" think that after 10 years, some kind of sludge, goo, or other icky substance has built up somewhere within the PCV system of our cars. This substance is, perhaps, not liquid but sort of a gel, foam or mousse that contains a fair amount of water. During normal weather conditions (i.e. not extreme cold), the heat from the engine itself or the heat from the gases passing through the PCV lines prevents this substance from freezing up and blocking the PCV system. But, during extreme cold, the substance either freezes up prior to us operating the car (while it is parked outside in extreme cold), or the water vapour present in the crankcase gases gets caught up in this substance and freezes when we drive in extreme cold.

During the past 4 weeks, I've stored my car indoors. My garage temperature averages about +10°C (about 50° American). I thoroughly washed the engine (the valve covers, etc.) off a month ago, and I have not seen any evidence of additional oil film deposition on the valve covers, despite operating the car in air temperatures of -20° (about -5° American). This leads me to believe two things:

*1)* No permanent damage was caused to my car by this problem during my cross-continent drive in bitterly cold temperatures.

*2)* The problem is not recurring (in other words, it was an intermittent problem, it is not a steady-state problem.

*3)* I am tentatively thinking that the problem might be caused by parking the car outdoors overnight in extreme cold, rather than simply by operating the car in extreme cold.

Having said all that, all I can suggest to you is that you experiment a bit. Wash the engine off (Simple Green is great for removing the oil film, and I don't think it hurts other parts in the engine compartment). That will give you a clean engine to start with. Try parking it indoors overnight next time some seriously cold temperatures are forecast, and see if the problem returns. If not, leave it outside overnight the next time seriously cold temperatures are forecast, and see if the problem returns when the car is cold-soaked prior to starting it.

I don't know how much PCV valves cost, where they are, how many are needed, and what the labour cost is to replace them. If it is not too expensive, I suppose you could replace the PCV valve(s) and then see what happens. But, although I think both your tech and I agree that the cause of the problem is a (likely temporary) blockage in the PCV system, neither one of us have figured out exactly where that blockage is happening, or what is causing the blockage. Until we can nail that down with some solid evidence, I don't think it is a good idea to start replacing parts.

As for the valve cover gaskets - I would not go there yet, unless you are having a problem with oil vapour leakage every single day you drive the car, without regard to temperature.

Michael


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## MN Flats (Nov 24, 2011)

I just found this other similar thread from way back:
http://forums.vwvortex.com/showthre...-driving)-V8-engine-frozen-crankcase-breather

Michael, I completely agree with your kinda-sorta thoughts... and I don't criticize the shop at all. Although they specialize in German cars, they have dozens of models to deal with and don't have the luxury of focusing on one rare bird like we do, and connecting the dots from posts on a forum. 

I was surprised when they told me just to change out the valve(s) would be nearly $2K by itself. Does anyone know the procedure and where these things are located? I also wonder if that is going to really help that much, as it seems to be a cold-weather-related problem that occurs quite early in the life of the vehicle (see thread above).

Dan


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## PanEuropean (Nov 3, 2001)

Hi Dan:

I don't know where the PCV valve(s) are located on the W12 engines. Next time I go to my dealer (probably tomorrow or Saturday, I have to install a new battery) I will ask the techs to show me this part, then I will take a picture of it and post it here.

There is an interesting comment about insulation of the PCV valve tubing in that discussion you cited above (Loss of engine oil (leak while driving) - V8 engine, frozen crankcase breather) - have a look at the second half of post #21, starting just below the illustration of the wiring diagram. I don't know whether or not our W12 engines have a similar configuration... but I will find out from the dealership.

Good work of you finding that earlier discussion - that kind of supports the theory of freezing in the PCV system being the cause of our problems. FYI I re-hosted all the photos in that discussion.

Michael


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## PanEuropean (Nov 3, 2001)

Here are two pictures of what I _*think *_might be the PCV valve on the W12 engine. It appears that there are two valves, one on each side of the engine.

Michael

*PCV Valve?
*


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## jyoung8607 (Feb 14, 2006)

PanEuropean said:


> Here are two pictures of what I _*think *_might be the PCV valve on the W12 engine. It appears that there are two valves, one on each side of the engine.


Your first picture, the brand-new motor, is a BRP (or the Euro equivalent). It has the simplified PCV system. Your arrow is sitting on the throttle body electronics. The PCV valve is the rectangular box slightly further forward partly covered by the oil filler neck. Note that it has two hoses to the valve cover: one curving around from the top front, and another to the bottom center.

Your second picture is from a BAP (or the Euro equivalent). Notice the entirely different puck-valve on the side of the intake. I don't have a BAP but I believe there was a lot more plumbing going on for BAP, most of it not shown in that picture. It might be why the system was revised - much less external tubing making it less susceptible to gunk build-up and freezing.

Jason


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## jyoung8607 (Feb 14, 2006)

I found some good illustrations of the BAP PCV arrangement in SSP 248. Lots of tubing, some distance from the warm engine and exposed to some very cold air in winter. The air in those PCV tubes will be full of oil and water vapor (a byproduct of combustion).

On the BRP, that little box on the side of the intake is the separator. Ventilation is from the tube on the front like on BAP. Separation of oil and vapor is done in that box. Liquid oil is returned through the valve cover rather than down at the oil pan. Only 6 or 8 inches of tubing instead of all that.


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## MN Flats (Nov 24, 2011)

Excellent pictures! Does it make sense then that the freezing/plugging-up is actually happening down at the separator and not at the valve itself? 

Also, would both of them have to freeze up at the same time to cause a problem?

Dan


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## jyoung8607 (Feb 14, 2006)

MN Flats said:


> Excellent pictures! Does it make sense then that the freezing/plugging-up is actually happening down at the separator and not at the valve itself?


It seems likely to me. However, it's total speculation and I've never laid eyes on a BAP engine - mine is a BRP.



MN Flats said:


> Also, would both of them have to freeze up at the same time to cause a problem?


If the plumbing on a BAP works exactly as pictured, probably yes. The two sides are joined by that piece in the center-top, therefore gases could go either way. Of course, that could work against you. If one side starts to frost up, flow rate would drop as gases go the other way, which would allow the constrained path to cool down a bit. That would just accelerate frost formation because there's still some humid air there, and eventually the constrained path blocks up. Then you have half a PCV system at best.

Jason


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## Gabs08PHTN (Jan 6, 2011)

Hi guys,
The VW Relay and Fuse Location document posted elsewhere in this forum states on page 1/7: *59 - SB59 - Fuse 59 (in fuse holder) 10 A - N79 - Positive Crankcase Ventilation (PCV) Heating Element (where applicable)*.
So it seems quite likely that VW was aware that there could be a freezing problem in the PCV system, now the point is whether your cars had this element fitted or not as VW quoted "where applicable".

Gabriel

P.S. Looking through old threads I came across this. Have a look at post #21 It seems that the only engine that had the PCV heater element was the 3.2 V6.


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## pgoober (Jan 4, 2009)

*Are we looking at a reasonable maintenance item?*

All, 
I have been reading these threads with interest and wondering if a combination of normal crudulation of the PCV separator (and/or tubes) and the greater release of blowby gas as our engines age will mean that we increasingly see this problem. Normal wear in the engine should mean more combustion gas, and therefore more water, gets released for each push of the pistons. This has been a particularly cold winter for many of us in NAR. Perhaps this has exposed that the PCV system is not fully functioning in some cars. I wonder if there is some degradation power and increased wear for our cars due to inefficient PCV operation all of the time, and only when ridiculously cold do we see the evidence of failure (oil splatter, presumably from an ice oil gel or plug). I also wonder if we risk a greater repair bill/failure of other systems when the PCV gets restricted and engine pressures rise. 

Is it reasonable to propose that it is the PCV valve that is plugging? Is it more likely one of the hoses further from the engine? And, should it be the valve itself, could this be a $100 item (2x for W12 owners) that needs to be replaced as a wear item more often as the engine ages?

-BD


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## PanEuropean (Nov 3, 2001)

pgoober said:


> ...wondering if a combination of normal crudulation of the PCV separator (and/or tubes) and the greater release of blowby gas as our engines age will mean that we increasingly see this problem.


Hi Brian:

I think your proposition above is correct. My guess, at this stage of the game, is that the separator valve is the thing that is likely contaminated with goo / ooze / crud / slime, this as a result of 10 years of use, and that is what is causing the problem.

As soon as I get the time (and can book a service bay for the day at my VW dealer), I intend to remove the whole PCV tubing and valve system from my BAP engine and inspect it to find out where the blockage is occurring. I don't think that will be a particularly easy job, simply because everything is packed into the engine compartment so tightly when the W12 engine is fitted. I might have to try and access that separator valve from below the car, rather than from the top down.

Hopefully once I find the location and cause of the blockage, I will be able to just clean all the parts up (in other words, remove the goo / ooze / crud / slime), and that will be sufficient to solve the problem. I kind of doubt that these parts wear out - I think that they just 'crud up', and if they can be cleaned, they will return to optimum performance in any temperature condition.

But... so far, everything I have written above is just speculation / hypothesis. It appears that the cause of the escaping oily vapours is a blocked PCV system, but we have not proven that 'for sure' (with hard evidence) just yet.

Michael


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## rjm0831 (Sep 19, 2009)

*Oil Smell in Cold temps*

Commoto and MN Flats (and, by extension, Michael):

I, too, have endured the latest cold snap here in Minnesota as I reside in Minnetonka. Recently, I also started experiencing the faint odor of hot or burning oil. I haven't done a once-over just yet but hope to this weekend now that the weather has warmed up. If need be, I plan to take my car into the tech that I use here locally, Paul Dufour of Dufour Automotive in new Hope. He is a Porsche master Mechanic and has done a number of things on my car that has saved me considerable expense. Plus, he will provide free use of a loaner.

I'm hoping that the faint odor amounts to nothing but it is very interesting that it just developed over the course of our 50+ days of sub-zero temps. 

Micheal, as always, thank you for your excellent advice and feedback. I will be sure to provide any additional details to this thread that I may learn during my investigation. 

Ron


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## ewb4arch (Jul 25, 2012)

*Any update on the PCV/gasket speculation?*

Last week it was rather cold here in northern IL and, unfortunately I experienced the same issue as described but the first post in this thread. The photo in that post could be of my car for how similar it looks (other than the V8 badge on mine being missing).

Car was parked outside last week with temperatures below 0°F and I commuted for 45 minutes going 60-70 mph. Definitely smelled the oil once I slowed down. Rather than repeat what's already been described by Comoto, I'll cut to the chase.

What do I need to do to solve this problem? I just spent ~$4000 on new front suspension and a wheel bearing assembly and don't have any more funds to take it somewhere so I'll need suggestions for what I can do myself. Part numbers for the PCV system? Any other diagrams out there to help me to replace them? Something else I should do first?

I'm driving my truck for the time being, but miss the heated seats and heated steering wheel in the Phaeton!

Thanks,
Eric


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## ewb4arch (Jul 25, 2012)

*Replaced PVC valve - Still massive oil leak(s)*

So when I replaced the PVC valve a LOT of water came out of it. It has warmed up so I figured this was the problem. So I topped the oil off and drove the car as normal. Unfortunately two days later the burning oil smell and then the check oil level light came back on.

I took the plastic shield off the bottom of the engine to find it and the both sides of the engine covered in oil. I suspect the valve cover gaskets must have failed when the PVC system was frozen. Is there any way to test/verify that before pull everything apart and replace them? Could it be something else? 

I'd appreciate any thoughts/theories.

Thanks,
Eric


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