DIY: 1998 528i S.A.S Pierburg Air Pump Maintenance and Rebuild Info
* Look up how S.A.S. works, basically at cold start, the S.A.S. Air Valve opens and the Air Pump injects extra air into the exhaust system to reduce polution.
* When Air Valve fails in OPEN position, exhaust flows backward into the Air Pump with water vapor, destroying the Air Pump.
Then no extra air is injected into the exhaust system at cold start, the ECU will register a P0410 OBD-II Code (S.A.S. Fault)
because the O2 sensor does not sense a change in readings as programmed.
* Best is to prevent damage to Air Pump: Every 80-100K miles:
- replace the Air Valve as there is not much lifespan remaining.
- replace the vacuum hose, use only thick-walled vacuum hose to prevent hose collapse under vacuum suction.
I also own a 1998 Volvo V70, and the Volvo Air Pump is also made by Pierburg, so the idea is the same. The BMW and Volvo Air Pumps are very similar (almost 95% the same). Actually with this info, you can apply to any European Cars (VW, Audi, MB etc.) with this setup of Pierburg Air Pump.
1- To replace the Air Valve. This is a 10-min job.
- Air Valve is #14 (It varies from year to year),
Gasket is #15. Vacuum Hose (use any thick-walled vacuum hose that matches size)
- New Pierburg Air Valve is $107 at EACTuning:
- Make sure you don't over-tighten the 10-mm nuts.
Look it up but I think the torque is 10 Nm
, basically snug and tug a bit!
*** Now if you read Step #1 above and change the Air Valve and its hose every 80-100K miles, you don't need to read further. Info below is for those who want to tackle the Air Pump should it become defective.
2. To REMOVE Air Pump for rebuild:
- Front Passenger Tire off
- Passenger Front side on Jackstand
- Front Wheel Vinyl Fender off (8-mm screws)
- Using a Long Extension and Ratchet, remove the 3 screws (10-mm) holding the Air Pump BRACKET. Do not
touch the 10-mm nuts holding the Air Pump to the BRACKET because you will regret you did that!
- Disconnect Hose Clamps and Electrical Connector and the Air Pump will come out.
3. To REBUILD Air Pump.
Rebuild only if you are short of budget and has the skills/desires to do it. With proper tools, it is easy.
Without proper tools ---> order new Air Pump!
Information is included here for those who have the skills and tools.
- Follow the instructions in the attached pictures:
- This is from my 1998 Volvo V70 but it is the same for BMW E39, use 6 paper clips to wedge the flange and pull it out:
Here is the BMW E39 Air Pump:
- To drill out the Six (6) rivets holding the Air Pump, use a 5/32" drill bit, the rivets will come out nicely.
- Use liquid paper to mark alignment of Air Pump housing to make re-installation easier (don't you want your life easier?...
- To re-install, use #8-32, 1.5 inches long nuts and bolts. You need a tocal of Six (6), Hardware store sells this package for $0.99.
- After the nut is tightened (don't over-tighten the nut), I use a pair of vice-grips and crimp the protruding threads
on the bolts to prevent the nuts from working loose; kind of locking the nuts in (I did trick on my Volvo one year ago and the nuts hold tight).