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KrisL 06-27-2007 09:21 PM

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!

venky 06-27-2007 09:27 PM

Perfect job. I will do both of these including the plugs over the weekend and will post results.

jvr826 06-28-2007 12:02 AM

How many beers until you noticed 4-10hp at the wheels after using the MAF sensor cleaner? :yikes:

Vornado 06-28-2007 07:22 AM

Great write up, Kris. I was getting ready to clean the MAF this weekend actually, never done it before. I got rid of the K&N I had in there for quite some time and replaced it with an OEM paper filter again. I think the K&N oil f*cks up the MAF and clogs the intake somehow over time. I'm going to see if there are any noticeable results after I clean it. I think the HP claim is in regard to a dirty MAF already "robbing" you of power. It doesnt give you extra HP, just restores it to where it should be.

KrisL 06-28-2007 07:27 AM


Originally Posted by Vornado (Post 2471684)
It doesnt give you extra HP, just restores it to where it should be.

Yep. I took the car for a drive and it feels strong, but I'm not going to claim it feels stronger without any real measurements.

I'm pissed, I couldn't find my autoenginuity ODB2 code reader. It gives MAF sensor readings - I could have actually measured whether anything had changed or not - see if the MAF had a different reading for a given RPM and intake air temp.

Bimmer ese 06-28-2007 07:32 AM

Great write-up! Keep up the great work.

I too, am like a kid when I order parts. I want them like yesterday! Where do you order you parts from? I've had pretty good luck and service from Autohausaz.


KrisL 06-28-2007 07:43 AM


Originally Posted by Bimmer ese (Post 2471712)
I too, am like a kid when I order parts. I want them like yesterday! Where do you order you parts from? I've had pretty good luck and service from Autohausaz.

Yep, that's who I ordered from. The water pump and some other parts were on sale, couldn't beat the prices.

Vornado 06-28-2007 07:50 AM

Autohaus is smart.. They give you free shipping on orders over $50.. When I ordered a replacement washer pump & grommet, I was a bit short, so I ordered extra stuff and before I knew it I was up to $70. I ordered more to save a little. :) They have great prices. I mentioned them to my dealer parts guy once and he acted a little insulted, like how dare I be be so resourceful and I should pay full price at the stealer. Hah.

BMWE46 06-28-2007 08:48 AM

Great write up Krisl! I too will be doing the MAF this weekend. i had nothing really planned, but after reading this thread my saturday morning now belongs to mein auto.

Vornado 06-30-2007 11:02 AM

I just cleaned the MAF sensor this morning.. Didnt notice too much difference, but I only took it around the block. Took about 10 minutes to do.. It might be in my head, but the shifts seem smoother.

venky 06-30-2007 01:32 PM

I bought the MAF cleaner spray from local parts store and ATF fluid (Dexron III) from local BMW dealer. I will do this today evening. I dont have the tools to unbolt the 10mm bolts in step 2. I will visit Sears/Home depot and will buy a tool kit with a torque wrench.

KrisL 06-30-2007 02:21 PM


Originally Posted by venky (Post 2476938)
I dont have the tools to unbolt the 10mm bolts in step 2.

Yes you do.

There's a 10mm open-ended wrench in the tool compartment in your trunk! I'll work just fine. You only need to loosen them about 1/2 turn before you can unscrew them the rest of the way by hand.

venky 06-30-2007 02:51 PM

Oh, so the basic toolkit works in this case. I will do this later this evening and will post results.

venky 06-30-2007 05:37 PM

I went and bought a Siphon pump to empty the power steering reservoir. Thought that'd make the emptying process nicer and faster.. Will start DIY now.

venky 06-30-2007 07:22 PM

Okay, finally done with Power steering fluid flush. The fluid was very dirty. Did complete fill and flush three times.

First DIY done. No issues encountered. Siphon pump was a good choice. Will do MAF and Plugs tomorrow. Time for some beer!

Nick325xiT 5spd 06-30-2007 07:32 PM

Changing the PS fluid is something that always makes me want a mityvac.

That said, in my experience, I needed to fill at least ten times to really get fluid through the system. And even then, there was significant residue.

crowz 06-30-2007 09:46 PM

I bought one a week ago to work on a toyota camry for a friend. Handy little gadget, still havent used it for fluid draining yet, only used it to test vacuum ports on the camry.

venky 07-01-2007 03:15 PM

Cleaned the MAF today. Wasn't too bad of a DIY.

Blinky330XI 08-01-2007 06:07 PM

Thaks for the great write up!

smolck 08-04-2007 10:35 AM

I just went to do this on my 2000 323i with 119k on it and the power steering fluid was just as clean as the new mobil 1 synthetic ATF I bought. Hmmm, I love the guy who owned this car before me, he took great care. SHould note that I did not have to remove the airbox on my 323I, simply unplugged it, loosened 1 clamp and out she comes, no way did I want to remove the air box. Thanks for the write up!

robj213 08-04-2007 03:15 PM

So 1 bottle of the PS fluid is enough to do all the drain/fill cycles?

crowz 08-05-2007 02:45 AM

1 bottle of trans fluid not ps fluid :)

AJ330CI 08-05-2007 10:20 AM

Good job Kris.

Is there a way for you or any one who did use the spray the proper way to post a pic or a diagram showing where exactly to spray?


Yellowmann 08-15-2007 06:13 PM

Great info....

Rick Lee 08-15-2007 06:30 PM

I was able to remove my MAF without removing the airbox.

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