BMW Dead Battery
Q: Two weeks ago, the battery in my 2002 BMW X5 died while parked in the garage overnight. I knew I hadn't left anything on, and the car was jumped and worked fine. The next day, it happened again--no radio, no lights, nothing.
This time it wouldn't even take a jump. I had it towed to an auto shop--even though I had recently put in a new battery, the shop replaced it anyway and assured me they found nothing wrong with the electrical system. I went to pick it up, and it wouldn't start again. They tested the car again and said it must have gotten run down from sitting in the sun (for a day?). I went to pick it up again, and it still wouldn't start. Now the shop is telling me they don't have a way to diagnose what's draining the battery. They just have to monitor it. In this day and age, is the only way to find out what's wrong by watching what kicks on? This auto shop isn't a BMW dealership but is authorized by BMW.
A: I'm not sure about being "BMW authorized" outside of the Bimmer service department. But I am confident a good battery won't go dead spending a day in the sun. It's got to be one of two things. Either they don't know how to correctly test for a parasitic amperage draw on the battery or it's an intermittent problem, which doesn't show up while testing. That the battery is out of commission every time you try to pick up the vehicle has me favoring curtain number one. A parasitic drain is simply current being used from the battery with the ignition off, doors closed, lights out, etc. This is necessary to keep your clock right and FM presets intact, among other things. It's considered normal when the amperage draw stays below a certain limit--in your case, 40 milliamps. Get it to a BMW service department before you pull your hair out. The correct test procedures are somewhat complex requiring special tools, and there are a few relevant issues pertaining to your X5. There have been notable parasitic draw problems from iPods and cell-phones, along with an on-board control-unit failure, which can be difficult to diagnose.
Dinghy Towing Honda
Q: I recently purchased a 1998 Honda Passport 4WD to use as a dinghy tow vehicle behind my RV. The owner's manual states I have to remove the front and rear driveshafts prior to towing. A local mechanic who runs a towing service told me it would be all right to tow this vehicle with the transfer case and automatic transmission in neutral, as long as I stop every 200 miles or so to run the transmission through the gears for lubrication. Can you can clarify this?
A: Vehicle drivetrains vary in their reactions to being towed. The danger comes from a lack of lubrication within the transmission. While dinghy towing (four wheels on the ground), the transmission's internal gears are turning, similar to normal driving; however, when the engine isn't running, there's nothing powering the hydraulic pump, which circulates the transmission fluid and lubricates internal components. This results in excess friction, heat, and damage. Some manufacturers offer detailed instructions that allow for dinghy towing under specific speed and distance limitations, as your mechanic suggests. But that doesn't seem to be the case with your Passport (which is basically just a rebadged Isuzu Rodeo). If Honda and Isuzu are telling you it'll cause damage, remove the driveshafts, or else. The safest course of action is to use a trailer and keep it off the road altogether--or remove the driveshafts, which I'm sure will get old quick. A third alternative is a "driveshaft coupling" made by Remco (www.remcotowing.com). With the coupling installed, you can disengage and engage the rear driveshaft with the pull and push of a control cable routed under the driver's seat. This allows the rear axle to free-wheel without rotating the driveshaft and transmission. Remco's 1998 Passport kit will run you $450 to $800, with or without a complete modified driveshaft. Remco tech support claims that removal of the front driveshaft will not be necessary as long as the transfer case is kept in neutral.