Philes' Forum by Vic Lucariello

With the cold weather approaching, now is the time to do a little maintenance on your battery. I just did some on Joanne's 325 and my M3 as well as a couple other E30s.

Most E30s ['84 - '91 3-Series] have a trunk-mounted battery which resides behind the right rear wheel, under a black plastic cover/shelf. The battery sits in a plastic tray and has a vent hose to expel electrolyte fumes and any gas [eg: Hydrogen] given off by the battery. In addition, the battery is supposed to be held in place with a retainer bracket.

I suggest you remove both the battery and its support tray. Both can probably benefit from a nice washing with a baking soda solution or a commercial battery cleaner. Don't flood the top of the battery with the cleaning solution. Just wet it enough to clean it. Before you clean the battery, remove any corrosion from its terminals with a wire brush and some sandpaper. If you are a true self-respecting Bimmerphile, you have the special tool designed to clean battery posts and terminals. All of you should at least know someone to borrow such a tool from. If not, please send in your 'CCA membership card for me to destroy.

Remove the battery by first disconnecting its negative, or ground, cable followed by the positive cable. The ground cable is the short one which connects the battery to the car's trunk sheet metal. Before you do any of this, ensure you have eye protection on as well as long sleeves and a pair of household rubber gloves. In addition, ensure that the ignition key is removed.

Was the battery securely mounted? Was the retainer bracket even there? Was the battery held in place at all [Perhaps wedged in place with an old piece of Italian bread]?? Was the vent hose connected to the battery? Was the vent hose even there? Some of these cars are 14 years old and have had their batteries replaced at least once.

The vent hose is [was?] supposed to connect the battery to a plastic condensate chamber located below the battery tray. The chamber is supposed to collect any condensed vapors and discharge any battery off gas underneath the car through a hole in the battery well. I suggest you remove the chamber, empty any liquid, probably battery electrolyte [AKA: BATTERY ACID ], and flush it out with water.

Next use the special tool to clean the battery cable terminals.

Now you are looking at the shiny, clean, painted, uncorroded battery well. YE A H , R I G H T. Get your baking soda solution and thoroughly clean and dry the battery well. Then coat it with an acid-resistant material such as Eastwood Battery Tray Coating. If you discovered any bare metal during your cleaning, be sure to treat with a rust neutralizer, such as Rust-Mort, and prime it prior to hitting it with the Eastwood stuff.

If you found the battery well partially flooded, a likely source of the water is the tail lamp housing gasket. Now is the time to replace these gaskets.

Next take your nice, clean, dry battery, set it on the workbench, and check its electrolyte level by removing the 6 cell caps. Most batteries are marked with the normal level, and I'll bet yours needs to be topped up with D I S T I L L E D W A T E R . I routinely add the better part of a Q U A R T [!] of water to folks' batteries. If you have to add this much to yours, I suggest an overnight slow charge prior to reinstallation. If you have or can borrow a hydrometer, check your electrolyte specific gravity to ensure that the battery is fully charged. The electrolyte should be clear when you view it in the hydrometer. If it is cloudy or has brown stuff suspended in it, I suggest you replace the battery.

OK, we're almost done. Reinstall the condensate chamber, vent hose, battery tray, and battery. Put a daub of anti-seize compound on the 6 mm screw which secures the battery retainer bracket to the battery tray. Reinstall the battery cables, positive F I R S T, negative L A S T. Coat the terminals with a bit of grease to impede corrosion.

Phew! We're done! Start your Bimmer up, go for a ride, and congratulate yourself on a job well done. In my opinion, the only way to get this kind of maintenance done well is to do it yourself. It is just too time consuming for a professional shop to do in a cost-effective manner.

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 DAYTIME PHONE NUMBER. Also, please be patient, I try to return every phone call, but it sometimes takes awhile. The best way to contact me is via e-mail.

Copyright 1998 - V.M. Lucariello, PE