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Tuesday, August 20, 2019

Doug's Domain

Doug Vetter, ATP/CFI

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Friday, June 9, 2017

Another Low Mileage Oil Service

Late last month, after a couple unusually hot 90+ degree days, the heat wave broke and we were greeted with 65 degrees and overcast skies. I saw this as an opportunity to wake the E46 from its long winter slumber and perform an overdue oil service.

When I drained the oil I could easily see through the stream flowing from the oil pan, which is more than I can say for the E36 with similar mileage (due to the greater blow-by from the old engine), but once all the oil was in the drain pan it was completely opaque. I won't call it a pitch black but it was definitely a very dark brown.

Of course color alone cannot be used as a metric to determine whether an oil is beyond its service life but it is widely known that the byproducts of combustion lead to a build up of acidic compounds over time, hence the recommendation by all oil and automobile manufacturers to replace oil on a calendar time basis (typically 6-12 months).

With the E46 back in service I'll be able to use it as my daily this summer when I take the E36 out of service for a complete drivetrain overhaul.

Driver's Side Airbag Replaced Under Recall

(Image: Closeup of steering wheel with airbag removed)

Many people who own everything from a Honda to a BMW are now familiar with the infamous Takata airbag recall. My passenger side airbag was replaced under this program two years ago with what was considered the "final remedy" and the driver's side airbag was recalled shortly after that but, as the manufacturer couldn't produce units in sufficient quantity until now, my car has been on a waiting list for the driver's side airbag.

As I knew I'd need the E46 for an extended period of time this summer while my E36 is out of service I called my dealer a couple weeks ago to double check if they had my airbag in stock. To my relief they said yes so I made an appointment to have the defective unit replaced under BMW's recall campaign. In the interim, my brother scheduled his 2001 E39 for the same campaign but as it turned out his car was equipped from the factory with a different brand airbag and thus was not affected.

With the E46 in my technician's bay he removed the original airbag to verify it was covered by the recall, obtained a new airbag from the parts department, entered a bunch of data from the labels on the old and new airbags into BMW's computers and then wrapped up the job by pushing the new airbag home until the retainers clicked into place. All in all the job took less than 30 minutes and I was quickly on my way.

It appears that the "final remedy" Takata part still uses an ignitor based on ammonium nitrate but the chemical has been mixed with a desiccant designed to absorb the moisture that apparently causes the propellent pellet to disintegrate over time. I'm no chemical engineer but instinct tells me that because desiccants typically lose effectiveness over time this is probably a temporary fix rather than a permanent solution. I would not be surprised if these airbags are again recalled sometime in the next ten years if -- heaven forbid -- more explosions occur with the new airbags, but by that time my assumption is the number of cars still on the road equipped with Takata airbags will be significantly less and that will reduce the overall impact of the campaign.

I recall reading some time ago that airbags had an expected lifespan of 10 years. I thought it was because the bag, subject to the stresses of being folded for that long, could rip on deployment, much as parachute fabric does if not repacked frequently in accordance with FAA regulations. But it now appears that the reason is because we cannot trust the propellants in the ignitors to remain stable forever.

Mileage: 20860 [Oil Service @ 20846]