DIY - Engine air box and MAF boot - B6/7 S4 and B7 RS4

Why: Replacing the engine air filter is part of the normally scheduled maintenance. It is normal procedure to remove certain parts to perform other repairs.

Just in case, MAF is a abbreviation for Mass Air Flow.

Recommended Maintenance Interval:
Engine Air Filter: B6/7 S4 - 55K miles at first and then every 60K miles there after.
B7 RS4 - 35K miles at first and then every 40K miles there after.

Parts Required:
Engine air filter - if replacing for maintenance
Screw clamp for MAF boot elbow hose - if needed

These parts break easily while performing these repairs:
MAF boot elbow
Upper coolant line elbow
Suction jet pump

Recommended upgrade/better parts and other modifications:
K&N engine air filter
MAF boot from 034 Motorsport
Brass pluming nipple for the MAF boot - I got mine from Home Depot
Lower engine air box flapper mod

Tools Required:

Philips screwdriver
Flat head screwdriver or a 7 mm socket and ratchet
Side cut pliers/Dykes or a Pick tool


  1. Open the hood
  2. Remove the rear engine cover (the one with the Audi rings on it) and if there is a cover over the top of the engine air box then also remove that too. They both just pull right off.

  1. Remove the two Philips screws that hold the intake air snorkel to the core support. Then remove the intake air snorkel from the top of the engine air box and core support. Watch for the snow filter that is in the end of the intake air snorkel to fall out when you remove the snorkel.

  1. Loosen up the small coolant line from the engine side of the engine air box. Be careful to not pull on the coolant line very hard because the nipple of the plastic elbow of the upper coolant line likes to break off.

Picture of the coolant line elbow for reference:

  1. Disconnect the hose from the front of the engine air box for the secondary air injection. Push the two tabs together and then pull off the engine air box.

  1. I like to disconnect the plastic hose from the rubber fitting on the front of the cowl wall. I do this so that I can get more play to wiggle the suction jet pump and rubber hoses out of the way. Along with I am less likely to break other parts.

  1. Loosen the hose clamp from the small rubber line that goes to the MAF boot elbow. If that line has never come off before then it will have a one time use crimp style clamp that will need to be cut off or loosened with a pick tool and then replaced with a screw type clamp. Then slide the hose off the MAF boot elbow. Next loosen the clamp on the throttle body end of the MAF boot with either a flat head screwdriver or 7 mm socket and ratchet.

7a. Here is a picture of the brass MAF boot elbow that I have installed on my car so that I never have to worry about breaking that stupid plastic one.

  1. Loosen the hose clamp on the MAF/engine air box side of the MAF boot and then remove the MAF boot.

  1. Disconnect the electrical connector of the MAF sensor. It can be hard to get this connector off since it is difficult to see the tab. Here is the back side of the connector pictured for reference.

  1. This is not pictured but pop the plastic retainer off the top of the engine air box for the fuel line.
  2. Unscrew the two Philips screws that hold the top of the engine air box to the bottom.

  1. Remove the top of the engine air box. It pulls forward to clear the two Philips screws from the bottom of the engine air box, then move the fuel line out of the way, then pull the top of the engine air box out of the engine compartment.

  2. Once the top of the engine air box is out of the way then the engine air filter pulls right out. The engine air filter pictured below is the K&N air filter.

  1. If it is needed the bottom of the engine air box can be removed to make more access for other repairs. The late 2004 and newer S4s have a vacuum line that goes to the back and bottom of the lower engine air box for a flap that opens up another inlet for the engine to suck in air from. That vacuum line needs to be disconnected and it is easiest to do it from the plastic fitting right below the EVAP purge valve. There is an expanding pin on the left side of lower engine air box that holds it to the body of the car. Pop that plastic pin out, free up the wiring harness from the top of the lower engine air box, and pull the lower engine air box up and out of the engine compartment.

  2. A lot of people modify their lower engine air boxes to remove the flap or keep it always open to allow air to come in all the time. Here is a picture for reference.

  1. Then put everything back in hand tight.

The first and last three pictures where taken from a quick few google images.

Update: Added picture of brass MAF boot elbow for reference.

Why does everyone have to use photobucket to view pictures? Not all of us have $400 a year to view it.

You have that backwards, the person who uploaded them would have to pay for you to see them. It’s definitely frustrating for the reader, but I’m pretty sure there are few, if any, people that are enthusiastic about going back to every post they’ve ever made in the past and reuploading every image so we can see them.