Fixing Vacuum and Boost Leaks on 2.7 Turbo Audi 

Thanks for the support! The PCV relieves the pressure that can build up inside the crankcase due to blow by gasses that escape the combustion chamber through the piston rings. As your engine wears more blow by is created due to the larger gap of rings. If the crank case was fully sealed the pressure that builds up inside can cause seals to fail. In the old days they used to just vent it to atmosphere with a filter or hose that runs out of the way. Now, due to emissions controls the PCV now re-routes those gasses to the intake so it will re-combust and thus lower emissions. It is an emissions control device. It is crucial for the lines to be free and clear, overtime they can get clogged up with soot and cause pressure buildup. In these A5 audi's the connections for the spider hose can break and result in a potentially difficult to diagnose boost leak and oil leak. Hope that helps!

10 N-m or 7.4 lb-ft

I do not recall any excessive amount of carbon build up when the intake was off. My engine was relatively well maintained and low mileage (around 100k) but, some carbon deposits are pretty normal. Also there is really not an easy way to clean intake valves completely without the heads off and disassembled. I don't recommend trying because if you just try to scrape it away, you wont be able to clean the entire valve easily and the deposits that enter the engine can cause damage to the turbos.

@@ohnogoforit yea I was just wondering bc my car fouls the spark plugs pretty fast. I’m basically doing the maintenance you did but I also got new oil check valves for the crankcase , FPR , fuel filter. I also recently got the fuel injectors professionally cleaned and I installed new 02 sensors. I’m currently waiting for parts to put everything together. It’s always a waiting game with these S4’s

it could be something simple like the PCV sucking excessive amount of oil. What is your milage? Do you have to add oil between changes? if so how much and after how many miles? However, depending on mileage and prior maintenance it could be something more serious like worn piston rings or blown turbo(s). You should do a compression test to rule out the piston rings , the turbos would be harder to check for because you need to get to the exposed turbo impeller to check for excessive play/binding and oil contamination. Although if the turbos are bad enough it sounds like a bag of marbles or slight scraping sound when running. Can be hard to hear with aftermarket exhaust.

Also remove and clean the lower turbo hoses that go to the intercoolers when you do the PCV stuff. If it is the PCV or check valves throwing oil there will be oil that collects in these low points that it can continue to pull into then engine and burn even if the problem has been repaired.

@@ohnogoforit yea I did a compression test and everything was fine. I did replace the spider hose with a 034 Motorsports one. Going to do all that maintenance I mentioned earlier and get the car re tuned. I have also drained the bit of oil in the intercooler hoses as well.