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Tuesday, July 14, 2020

Doug's Domain

Doug Vetter, ATP/CFI

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Friday, July 20, 2007

Oil Analysis Results

(Image: July 15th BlackStone Labs Oil Analysis Report)The oil analysis results pretty much speak for themselves. I'd like to get this engine to 250K before I retire it and if my only concern were simple wear metals I'd say this data indicates I have a shot at meeting that goal.

Of course, the whole point of starting oil analysis was to track fuel or coolant in the oil, which could indicate any number of problems that if left alone could cause catastrophic engine damage. The report again mentions the high viscosity of BMW oil, but as I've said earlier this is normal and expected as BMW 5W/30 is really closer to a 5W/40 by design.

When I get a few more samples under my belt, I plan to import this data into a spreadsheet I use for aircraft engines to track and graph the trends. I'll publish that spreadsheet if there's sufficient interest.

Faint Front Wheel Noises

A few times I've pulled out of the driveway recently I've noticed a very faint rhythmic growl coming from the front right corner of the vehicle when making gradual left turns at a relatively low speed (< 30MPH).. That could be a lot of things, but it's most likely the tire or the wheel bearing. Since the tires are only 6 months old and in pretty good shape, while the wheel bearings have almost 150K miles on them, I'm putting my money on the latter.

Replacement of the front wheel bearings costs about $500 a wheel at the dealer, so there's a lot of built-in motivation to do the work myself. The job is easily within the realm of a DIYer with my limited experience, but the task doesn't come without downsides. If everything goes as planned, I can do this job with little more than a breaker bar and a huge (46mm) socket. If things go awry, on the other hand, I'll need access to some specialized tools that are fairly pricey for the DIYer. Fortunately, I happen to know a cool technician that has offered to let me borrow whatever BMW tools I need.

Steering Wheel Noise

It's been faint for years, but now I have a pretty persistent, repeatable scraping noise coming from what appears to be the left side of the steering wheel. I've heard this can be the result of bearing wear in the steering column, but the sound happens at the same point in the arc as I turn the wheel. My technician hinted that this might be due to the wire spring (presumably in the slip ring component) that connects the airbag to the car's systems. Apparently, while the horn uses a circular contact and wiper arm / brush arrangement to maintain electrical contact when the wheel is turned, the airbag's wiring is more critical and is thus routed through a permanent connection in the form of a wire spring that winds up as the wheel is turned from the center position. As the tension in the spring increases, it can deflect and rub / scrape against something.

I believe the solution to the problem will be replacement of the slip ring. I believe you can order the slip ring assembly by itself, but I know that if you buy the wheel you get one by default. As I had plans to replace the wheel eventually due to some cosmetic damage to the leather (the result of nine+ years of normal and expected wear and tear), it makes sense to buy the wheel now. That, however, presents me with two options:

While airbags have no specified life limit that I'm aware of, I recall reading that when airbags where first conceived they were designed to last 10 years. Since I'm almost at that point, it seems foolish not to upgrade it so it actually does what it should do in the event of a crash (you'd be surprised at the number of airbags that simply don't deploy for one reason or another). On the other hand, I absolutely hate the idea of spending $1K on a freakin' steering wheel and airbag, but something tells me the sting of that expense won't seem as bad if I consider it an "upgrade" as well as a "fix". I have yet to decide what to do, but you'll see the results here, I can assure you.

Mileage: 446600