soundquest

Time to service my oil-leaking 2009 A8 4.2L. The infamous oil-filter/cooler housing leaks like a sieve (150K miles). What else shall I look at replacing while I am in there and have the intake MFD off and out of the way? Thanks in advance!

Mike141

With that mileage and since you’ll have the intake manifold off, might as well clean the carbon build up on those valves. If there are any issues with your injectors, now would be the time to address those also. Make sure you get intake manifold gaskets, valley gasket, and also the oil separator…079103161J valley pan gasket, 079103464F oil separator, 079103121BE N90959701 oil filter housing O-rings, and (2) 079133074B intake manifold gaskets.
you’ll need a bunch of clamps after removing the ones you have now on coolant hoses to get the intake manifold off. And yes, I take manifold will need to come all the way out to do this repair. It’s not that bad, just a lot of parts need to come off and it’s tight towards the back.

soundquest

Many thanks for the reply and guidance. What is your preferred method for cleaning those intake valves? I bet it completely changes the characteristics of the engine afterward (more power, more responsive, better economy, etc). Thanks.

Mike141

Preferred method would be walnut blasting, but not sure if you have access to that. I am sure there are shops in your area that would do it. The bulk of the cost is the labor to get to the valves. But if they are not that bad you can spray some solvent in there, let them soak and scrape the carbon off with some picks and brushes. It will just take some time and a bit more work. CRC makes a solvent in a spray "Intake valve and Turbo cleaner" or Seafoam should work. I'm sure there are other chemicals you could use, just be careful with plastic/rubber parts that can be destroyed from these chemicals.

soundquest

Thank you. Time to get outfitted with a walnut blaster and appropriate media (and pick tools long enough). I see many using the harbor freight blaster with decent results (although I am sure there are much better options out there though at increasing expense and diminishing returns). This is going to be a multi-day, multi-phase job since I do not have the time to do it all in one fell swoop. She will be a new car. Thanks again for the guidance.