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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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Old 06-27-2007, 09:21 PM
KrisL's Avatar
KrisL KrisL is offline
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Mein Auto: 330i ZHP
Inspection II part II - Changing PS fluid & Cleaning MAF

Edit: All 3 parts are online:
Inspection II part I: Changing your spark plugs
Inspection II part II: Cleaning MAF & replacing power steering fluid
Inspection II part III: Water pump, thermostat, belts, hoses, fuel filter

My water pump, hoses, pulleys, fuel filter, and thermostat should be here on Friday for Inspection II part III! Until then, I'm like a kid on Christmas morning when it comes to anything I've purchased for my beloved ZHP . I couldn't wait until then to change my power steering fluid and cleaning my mass air flow sensor!

Total time requred for both of these: 30-45 minutes including taking pictures.

Changing Power Steering Fluid

If you've hung out here for awhile, you'll see a lot of posts from people that need to change their power steering pump and hoses. I don't know if changing the fluid will actively prevent failure, but it should, right? Since changing the fluid takes about 10 minutes and under $10, it seems silly to NOT do it during Inspection II (60,000 mile service). BMW's power steering system uses automatic transmission fluid, but it is in no way connected to the transmission - it just happens to use the same fluid.

Parts/Tools required:
* 1 bottle of automatic transmission fluid (ATF) that meets Dextron III specifications
* 1 turkey baster (warning: it's better to purchase one of these dedicated for garage use. Using the one out of the kitchen will mean buying a much more expensive Kitchenaid turkey baster for your wife).

Step 1: Locate the power steering reservoir and unscrew the cap.

Step 2: Locate the ATF you purchased. My local auto parts store (Winchester Auto Parts rocks!) carried Meyle ATF-III manufactured in Germany.

Step 3: Use a turkey baster to suck as much fluid as possible out of the reservoir. I put it into a glass so that I could check it out. Black! It probably isn't the proper way to dispose of this fluid, but I just dump it into the 5 gallon used oil container that I drop off at the local auto parts oil recycling container every few months.

Step 4: Re-fill the reservoir (don't overfill!). You'll need to place the cap in a few times, removing it to examine the level. When full, screw the cap back on. Here's the fill mark:

Step 5: Start the car. Move the steering wheel from full lock left to full lock right at least 4 times.

Step 6: REPEAT STEPS 3, 4, and 5 - Several times! The power steering system contains a lot of fluid - if you have a Bentley manual, check out the diagram showing the entire power steering fluid cooler that runs along the steering rack. I drained-and-filled 3 times - until my 1 quart ATF bottle was empty.

This picture was taken the second time I removed fluid. You can already see that it's turning dark red - the color of the Meyle ATF.

Make sure the cap is back on and the fluid is correct - you're done! It's also a good idea to make sure the cap and the reservoir are clean of dirt while you're at it. Don't want anything contaminating that fluid.

Cleaning the Mass Air Flow Sensor

The mass air flow sensor (MAF) senses how much air is coming into the engine. The DME uses this information to calculate how much fuel it should be putting into the injectors to maintain the proper air/fuel ratio. Over time, the tiny super sensitive resistor in the MAF can get dirty - this causes it to not detect the proper amount of air. This can cause erratic idle and loss of power and gas mileage. Cleaning the MAF is even more important if you've got a cold air intake with an oil filter - the oil will collect on the MAF. These instructions are for the factory intake.

Parts/Tools required: 10mm socket, flat-bladed screwdriver, CRC Mass Air Flow Sensor Cleaner spray, Lost Coast Brewery (Eureka, CA) Downtown Brown, bottle opener

Step 1: Disconnect the MAF wiring harness. I pulled up a little retaining clip slightly with a flat-bladed screwdriver to help me pull it out:

Step 2: Unscrew the two 10mm bolts holding the airbox in place. Use your flat-bladed screwdriver to loosen the hose clamp (complete removal is not required):

Step 3: Remove air box. To do this, you'll have to pull the snorkels out of both the inlet and exhaust of the airbox. After you've done that, rotate it up and toward you from the rear until it comes free. Some jiggling may be required.

Here's a picture of the airbox coming out of the car, with the MAF pointed out:

Step 4: With the airbox out of the car, you remove the MAF by using your flat-bladed screwdriver to pry these retaining clips out of the way (two of them, one on each side):

Step 5: Follow the directions on the spray. It tells you to spray the entire screen and sensor down with fluid 10-12 times, being extra careful not to touch the straw to any metal parts. After doing that, I held it until I couldn't smell the fluid anymore (that's my method of determining if it had all evaporated ). Replacement is the opposite of removal. Getting the airbox into place can require quite a bit of jiggling, so be patient. I haven't found any tricks, it just takes a few times to learn how it snaps into place. Be careful to pull your MAF wiring harness aside before placing your airbox into place. It sucks when you discover it's stuck under there.. (not that I'd know...).

Step 6: Open and enjoy your Downtown Brown for a job well done!


Last edited by KrisL; 11-20-2008 at 11:15 AM.
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