Philes' Forum by Vic Lucariello

Hello, bimmerphiles! This month I want to spend some time revisiting a couple topics which I feel are quite important. [No, Ross, this isn't a rerun of some 10-year old column.]

Recently, I was working on a really nice 1996 328is. Beautiful car, burgundy [That's the color my 2002 is supposed to be.], tan leather, alloys, with about 50k on the odometer. I shouldn't have to tell you that it is a 5-speed 'stick'. I was checking the brakes and changing the brake fluid, so I needed to remove the wheels. Simple, no? Read on....

The wheels were plumb stuck to the hubs! All 4! How could this be, you ask.

Note that I said 'alloys', referring of course to the aluminum alloy wheels. The hubs to which these alloys mount are of ferrous material. Hmmm.....dissimilar metals in contact with each other. If I recall my undergraduate metallurgy, or was it chemistry?, all we need is some electrolyte [maybe some rain water/road salt solution?] to intimately connect the two metals and we can generate some really nifty galvanic action! [Maybe add a little heat from the brakes?] Just like that in your car's battery! Except that the galvanic action in the battery is desired.

My first real world exposure to unwanted galvanic action on an automobile was when I made up some aluminum patches and pop riveted them to the rust holes in my Father's 1961 Mercury Comet. Same thing happened, except that the aluminum patches were much thinner than alloy wheels, so the patches simply corroded through and fell off. My Dad was not pleased. He bought himself a Cougar and gave methe Comet!

Anyhow, getting back to the 328, it took Jr. and I nearly a half-hour to get the dang wheels off. We got the biggest dead-blow hammer in my tool box, and Jr. repeatedly hit the inboard side of the rims while I slowly spun the wheels. I honestly thought that one or more of the alloys would be damaged in the process, but none were. I feel that it is unlikely these wheels could have been removed in a roadside setting with the car up on its jack.

Preventing this problem on your Bimmer is pretty simple. All you have to do isput a coat of anti-seize compound on the wheel hubs and the 'hubcentric' bores in your alloys. I suggest you wire brush the surfaces prior to applying the anti-seize, which is available at any auto parts supply house. If you have a shop do your work, be sure to explain to them what you want. The stuck wheel problem [The 328 was the second-worse case that I have seen. The worst one required a torch!] has been common on Bimmers since BMW began fitting a lot of the cars with alloys. If the shop is unfamiliar with the problem or its solution, perhaps they shouldn't be working on Bimmers, especially yours. Incidentally, the problem occurs on all cars with alloy wheels and close-fitting hubs, not just Bimmers.

The other topic I want to readdress is that of brake fluid and its need for periodic replacement.

You will note that the driver school tech form requires that your brake fluid be less than 6 months old and that you must indicate on the form the date when the fluid was last changed. The reason for this is that the DOT 3 and DOT 4 brake fluids commonly found in Bimmers are glycol-based and are hydroscopic. Hydroscopic means that they have an affinity for moisture.

This absorbed moisture, which enters the fluid via the master cylinder reservoir vent and system seals, and even, some say, via the brake hoses, causes corrosion [Ever price a new ABS unit?] and lowers the boiling point of the fluid. Boiling brake fluid is a bad thing! It causes partial to complete loss of your brakes, which depend upon having a relatively incompressible fluid between the master cylinder and the brake calipers in order to work as Archimedes intended them. Brake fluid vapor, like most vapors, is highly compressible! Ask me how I knowthis!

Now that we understand why we need to periodically change our brake fluid, the next question is how. Judging from what we see in our driver school spot-checks, there is a bit of confusion regarding what is involved in a brake fluid change. Some folks think that bleeding the brakes is the same as changing the fluid. This ain't necessarily so. Although a proper fluid change should result in any air being purged from the brake system, simply bleeding the brakes will not change the fluid.

A brake fluid change should begin with removing all the old fluid from the master cylinder reservoir. While this is easy on a 2002 or 320, newer cars require a bit more time. I use a hand vacuum pump with a tiny piece of tubing which can snake its way to the farthest reaches of the reservoir and remove all the muck from the bottom. Incidentally, if you have muck at the bottom of your reservoir, you're not changing your fluid often enough!

Next refill the reservoir with the fluid of your choice, DOT 4 for most of you, and connect a pressure bleeder filled with the same fluid. Use only fresh fluid from a sealed container, and remove any old fluid from the bleeder. I have used the pedal-pumping, vacuum pump, and pressure methods of changing fluid, and I have settled on the pressure method as being the best. I guess I could devote an entire column to comparing the three methods, and if there is interest, I will, so let me know. There is an inexpensive pressure bleeder advertised in the Roundel which, by most accounts, works well.

Next, connect a hose and catch bottle to the right-rear bleeder screw and let out enough fluid so that the fluid entering the bottle is the same color as the nice fresh stuff you put in the other end. Most commonly-available DOT 4 fluids are clear to light amber in color when fresh. They darken as they age and absorb moisture. Some of the specialty brake fluids are relatively dark to begin with, so this rule of thumb doesn't apply. In these cases, remove about 6 oz. of fluid per wheel.

I would be remiss, and Ross would no doubt chastise me, if I didn't include my standard warning for you to make sure the car is securely supported on jack stands for this operation. Also, wear eye protection! Brake fluid burns eyes like crazy [galvanic action?]! Ask me how I know this!

Do the same thing for the other three wheels [don't forget the clutch slave cylinder!] keeping the level in the bleeder and reservoir adequate, and you're are done! Before you reinstall your wheels, start your engine and firmly apply the brakes a few times to ensure you haven't inadvertently gotten any air into the system, then check the bleeder screws to ensure they are tight and not leaking.

If you have your brake fluid changed by a shop, be sure to establish in advance what you are paying for and what you expect them to do. Don't ask them to simply bleed the brakes. Tell them that you want the fluid changed and why. Also, I suggest you find out in advance what fluid changing method they use, and avoid shops which do not use the vacuum or pressure methods. Moreover, if you supply your own brake fluid in sealed 12 oz. containers [bring 4], you can be sure that you are getting the freshest fluid possible. If the car is going in for other service requiring wheel removal, I think that an additional labor charge of 1/2 hour should cover the brake fluid change as I have described it. Want my advice? Heck, if you read this column you probably do. Do it yourself!

Anyone wishing to contribute to Philes' Forum should contact me via the info on the masthead. I'm interested in tech tips, repair /maintenance questions and/or tips, dealer horror stories, product evaluations, etc. Please call before 8 PM, and if you leave a message, PLEASE INCLUDE A PHONE NUMBER WHERE I CAN REACH YOU ON WEEKDAYS. Also, please be patient, I try to return every phone call, but it sometimes takes a while. If you don't hear back from me within a few days, please call again. The best way to contact me is via e-mail.

Copyright 1999 - V.M. Lucariello, PE