[bluedoggiant]

So the Touareg AXQ 40v 4.2 V8 uses a slightly modified PCV system to the Audi/Phaeton system. Below is a super high level description of how (I understand) it works, someone feel free to correct me ( I know the arrow from the intake manifold is in the wrong direction):

One of the main differences between the two versions is the crankcase baffle plate in the valley is designed for off-road use in the Touareg. The crankcase baffle plate does double duty as the valley pan gasket.

Unfortunately, for those with leaking valley pan gaskets, the Touareg part is NLA, however the Audi/Phaeton part is widely available. It will fit, but it is different, and sure enough I found this little text blob describing the change in one of the lesser known and older VW 4.2 SSPs (Course number 89s303):

Below are the two parts side by side with annotations of difference:

Below is how I am considering modifying the Audi part to copy the Touareg part design.

Below is how it looks in the engine valley. The Touareg and Audi/Phaeton 4.2 are virtually identical, with the same holes in the same places, except the Touareg has this additional casting at the front (poorly circled). I cannot figure out it’s purpose, if anyone knows, I would love to be enlightened:

My theory is that VW moved the large opening toward the front of the baffle plate so that in scenarios where the vehicle is on a steep incline, that oil splash black will not get sucked up into the PCV valve. I also think they added additional drain holes at the rear to more quickly drain oil back into the crankcase to eliminate oil sucking up into the PCV valve. Honestly, it seems like the Touareg design is better for all applications, so it's a shame that it’s discontinued, assuming my theory is correct. Does anyone have any thoughts on my analysis?

As for my proposed modification, does anyone have any opinions as to whether I am overcomplicating this or potential downsides? Clearly VW thought it was worthwhile enough to include a different part here.

Finally, if I were to use the Audi part unmodified, can anyone foresee issues with the ECU? I certainly do not want to create any situation where I increase crankcase pressure, cause engine damage, and/or blow out any seals, of which I suspect the miserable-to-replace oil cooler seals would be the first to go.

The rubber gasket does not appear to be removable, and it seems integrated into the part and may mess with bolt tolerances, even if I were to try and remove and apply RTV. I also wonder how steep does a grade need to be for the baffle plate to become an issue? I definitely put my Touareg on steep grades off road, but am seldom testing the absolute limits.

Any and all input appreciated

 

[MidnightTouaregV8]

It is a brave new world...
I doubt ECU has direct control over oil or crank case vapor circulation.

 

[bluedoggiant]

It is a brave new world...
I doubt ECU has direct control over oil or crank case vapor circulation.

I know it does not, but wasn’t sure if there were any sensors that would be upset as it relates to crankcase pressure

 

[casioqv]

Any idea why it's leaking? Generally these type of silicon gaskets are extremely unlikely to leak, and can be reused and reinstalled indefinitely. I've reused a lot of valve cover gaskets in that style with no leaks in the past. Do you see damage to the silicon seals? Can you measure or detect any warpage, scoring, or grooves in the two surfaces that it bolts between?

Personally, I'd probably just use the AUDI plate as is, and not worry about it. It still has holes in the front and rear for oil to drain down. Worst case scenario, you'll burn a little oil and smoke a bit if using the maximum rated hill descent or ascent angles for an extended time period.

I agree the Touareg design seems slightly better, it's a shame they didn't just use that one on all of the vehicles.

 

[bluedoggiant]

Any idea why it's leaking? Generally these type of silicon gaskets are extremely unlikely to leak, and can be reused and reinstalled indefinitely. I've reused a lot of valve cover gaskets in that style with no leaks in the past. Do you see damage to the silicon seals? Can you measure or detect any warpage, scoring, or grooves in the two surfaces that it bolts between?

Personally, I'd probably just use the AUDI plate as is, and not worry about it. It still has holes in the front and rear for oil to drain down. Worst case scenario, you'll burn a little oil and smoke a bit if using the maximum rated hill descent or ascent angles for an extended time period.

I agree the Touareg design seems slightly better, it's a shame they didn't just use that one on all of the vehicles.

Thank you for your reply.

Well, I can't know with absolute certainty how/if its leaking, but my valley is very crusty with the same kind of grime build up in the two examples above, which can only be caused by escaping oil vapors and dirt adhering to it. I just don't see any other possible orifice it could be leaking out of. When I say leak, I really mean sweating, I don't believe I am actually losing oil. I do wonder how much crankcase pressure is escaping through the seal. I have not pulled mine yet, so I don't know the condition of the seal or if there is warpage. If anything were to be warped, it'd be the cover, I'll check when I pull it:

I received the Audi part, I can't tell if this is silicone or rubber honestly, but we will see the condition of the gasket when I pull it. Seems like the lower left bolt hole on the unit I received got some additional rubber/silicone on it, think I should pick it off before install. The main reason I am doing this job is to replace the oil check valves underneath.

I don't know anything about welding, I'm not even sure how well you can weld a plate to this type of alloy. I am still debating drilling additional holes in the rear like the Touareg unit has. No idea why the Touareg holes are on the left and Audi hole is on the right.

I really don't know why they couldn't just supersede the Audi part with the Touareg part. Do you think using the Audi plate will increase crankcase pressure? That's my main concern. The two small holes. 😅

 

[casioqv]

I don't think it will increase crankcase pressure, that presumably goes through the large center hole. The small holes are probably just for oil to drain back down.

Personally, I'd visually inspect everything and make sure I understood how it works and how the oil and gases flow, and then you will hopefully be reassured that the Audi version is fine.

 

[bluedoggiant]

I don't think it will increase crankcase pressure, that presumably goes through the large center hole. The small holes are probably just for oil to drain back down.

Personally, I'd visually inspect everything and make sure I understood how it works and how the oil and gases flow, and then you will hopefully be reassured that the Audi version is fine.

You're probably right, I'm just paranoid. Like you said, likely at worst oil may get sucked up to the pcv valve if on a steep incline for extended periods.

I did as much studying as I possibly can, I think I have a pretty decent understanding at this point. I will say though, PCV design can be a bit of black magic. In the VW/Audi 2.0T world there are COUNTLESS variations of the pcv system with minute variations that have proven to make a big difference in performance.

I'm going to go ahead with the job in the next week or so and update here how it goes.

 

[bluedoggiant]

I performed the repairs over the weekend, attached are photos of the two plates side by side. I can confirm that the plate uses rubber, not silicone, for a gasket. It had hardened and plasticized, so it is not re-usable.

As for the additional casting on the Touareg block I mentioned in my OP, it appears to be another drain hole down into the crankcase for when the vehicle is being operated on steep declines.

I also noticed my valley was cast with a hashed texture unlike the Audi and other Touareg valleys I posted above, which are totally smooth.

I must say, my engine is fairly clean compared to others I've seen, but there was still a TON of crud built up in the PCV lines and had encrusted itself on the old baffle plate.