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Audi A4 Auxiliary Air Pump Replacement
 
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Pelican Technical Article:

Audi A4 Auxiliary Air Pump Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$375 to $600

Talent:

**

Tools:

10mm wrench

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New auxiliary air pump, hoses

Hot Tip:

Careful working with the hoses, as they get brittle

Performance Gain:

Won't leave you stranded at the side of the road

Complementary Modification:

New V-belt

Emissions concerns have become a very important part of modern cars. Unlike in the cars of the past when very little concern was paid to what came out of the tailpipe, modern cars have very strict restrictions on the emissions they can produce. Manufacturers must produce cleaner burning cars along with trying to stretch every mile they can from a drop of gas.

One of the issues with the emissions systems on these cars is that everything must work in harmony for the cars to pass a SMOG test. If your car is having a hard time passing a test, one of the issues may be the Auxiliary air pump.

The secondary or auxiliary air pump is part of the emission system and is used to inject fresh air behind the exhaust valves during the engine warm up. The filtered air is drawn in from the air box and pumped to the combi valve on the cylinder head. The air produces an oxygen rich environment that assists in after burning and helps the engine run cleaner.

If you are having trouble passing a smog test, it may be the secondary or auxiliary air pump or system.

The air pump (red arrow) is located at the lower front right of the engine between the oil filter and power steering pump.
Figure 1

The air pump (red arrow) is located at the lower front right of the engine between the oil filter and power steering pump.

There are two hoses attached to the pump.
Figure 2

There are two hoses attached to the pump. The intake hose (yellow arrow) draws filtered air from the airbox. The outlet or pressure hose (red arrow) sends air to the check valve by the cylinder head. To test the pump, remove the pressure hose (red arrow) on a warm engine and start the car and allow it to idle. After approximately 20 seconds, the air pump should run and you should feel air coming from the outlet. Use caution when working with the hoses, as they become extremely brittle with age and are very expensive.

If the pump does not run, remove the electrical harness from the pump and check for voltage at the connection (red arrow).
Figure 3

If the pump does not run, remove the electrical harness from the pump and check for voltage at the connection (red arrow). Start the motor and allow it to idle. You should get an electrical signal after about 20 seconds. If you are not getting power at the harness, you want to check the fuse. If the fuse is good you will want to replace the relay.

If the electrical components are all good and the pump still does not work, you probably need to replace the pump.
Figure 4

If the electrical components are all good and the pump still does not work, you probably need to replace the pump. Begin by disconnecting the two hoses; squeeze the plastic clips (red arrows) and wiggle the hoses off the pump. Use care as the plastic hoses get brittle with heat and age.

If you skipped the electrical connection test, you must now disconnect the electrical connection by releasing the tab on the connection and pulling it straight back from the pump (red arrow).
Figure 5

If you skipped the electrical connection test, you must now disconnect the electrical connection by releasing the tab on the connection and pulling it straight back from the pump (red arrow).

Use a 10mm socket and remove the three 10mm bolts holding the pump in place (red arrows, two shown).
Figure 6

Use a 10mm socket and remove the three 10mm bolts holding the pump in place (red arrows, two shown). Slide the pump out from the bracket.

With the pump removed from the vehicle, you can see the inlet opening (yellow arrow), pressure opening (red arrow) and the rubber isolating bolts (green arrows).
Figure 7

With the pump removed from the vehicle, you can see the inlet opening (yellow arrow), pressure opening (red arrow) and the rubber isolating bolts (green arrows).

This photo illustrates that the intake hose (red arrow) draws fresh air from the air box.
Figure 8

This photo illustrates that the intake hose (red arrow) draws fresh air from the air box. The output hose connects to the metal pipe running to the combi-valve (yellow arrow). Use care when working with these hoses as they get very brittle. Installation is the reverse of removal.


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