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Monday, May 27, 2024

Doug's Domain

Doug Vetter, ATP/CFI

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Saturday, April 7, 2007

Spring Cleaning

I guess it's a sign of owning an older BMW that I consider three weeks a "long time" since I last logged anything, but following the recent valve cover gasket work the car has been running beautifully. That's not to say, of course, that I don't have work to do on it.

The next mechanical work I plan to do involves cleaning the idle control valve as preventative maintenance. When I perform a cold start the engine normally revs to around 1100 RPM and slowly works its way down to the normal idle speed of 600 RPM as the engine and exhaust temperatures rise. That transition is supposed to be smooth and gradual, but on a few of the colder mornings lately I've noticed the RPM move down in a stepped fashion. The effect is very subtle, to be sure. Most people wouldn't even notice it, but I do remember seeing that chracteristic years ago...right before my ICV got stuck and turned my throttle into a deadman's switch. As my technician told me recently when I queried him about this -- "they just get lots of carbon built up in them...it's not like the unit itself fails", so it seems to me a little TLC now in the form of a can of carb cleaner will do wonders.

I'm also planning to replace the secondary air pump check valve, again as preventative maintenance. The last one failed at roughly 60K miles in service and allowed exhaust gases to work their way back into the pump and destroy it. Since the air pump isn't exactly cheap, spending $70 on a check valve that's easy to replace seems like the right thing to do.

Oil Service with Oil Analysis

Things were so quiet with the car lately that I briefly lapsed into complacency. I was reviewing my maintenance schedule spreadsheet this week when I suddenly realized I'd accumulated over 4500 miles and it was time for another oil service. I picked up the parts at my local dealer Friday and performed the work this morning. Everything went as planned and I had it done in less than 30 minutes: 10 minutes to do the actual work and 20 minutes to let it drain. In other words, it was a pretty standard oil service.

Given that I passed 140K miles recently, however, I decided to do something a little less "standard" and put the engine on a oil analysis program. I'm looking for all the usual wear metals, but in particular I'm looking for coolant in the oil, as this would be a sign of a deteriorating head gasket. While this is the first time I've ever done an oil analysis on any car I've owned, I'm not new to oil analysis since I've used it in my aviation pursuits for years to make sure we recognize engine problems before they affect our operations. As we pilots say, the worst thing you can do is turn off the fan that keeps the pilot cool. Do so and watch him sweat!

As many proponents of oil analysis will tell you it's not so much the absolute values of the numbers in the report that are important in as much as the TREND of those numbers. In fact, it was the trend of certain higher wear metals over a couple samples on one of the airplanes I used to fly that pointed to defective rocker arm bushings. We pulled the rocker boxes off and found a couple bushings on a recently-replaced cylinder loose and wearing excessively. I don't really like to think what would have happend if we weren't doing oil analysis and had just continued to blindly turn the key every time we went flying, but the point is oil analysis isn't marketing -- it really works and is an important part of any preventative maintenance program. Automotive engines have become so reliable that I doubt there's much need for analysis in the first 75K miles, but it could be argued that the analysis is pretty cheap insurance, and the earlier you start the analysis the more trend data you have to diagnose potential issues later in the engine's life.

While I don't plan to do it on a regular basis I ordered a Total Base Number (TBN) test for an additional $10 (total of $30). This will tell me how much life the oil has left in it after running in my engine for 4700 miles and it should satisfy my curiosity as to how well BMW oil stacks up against other oils in terms of longevity. It will probably be a week or so before I get the report, but I'll post it here when I get it.

With a 10% CCA discount and state sales tax of 7% essentially erasing that, I paid $41 for 6 quarts of BMW 5W-30 Synthetic and the filter kit. The oil analysis is normally $20 and the TBN test is $10, or $30 total. My dealer gets 0.6 hours to do an oil service, which at current labor rates & tax amounts to a labor savings of $77. Not much, but better in my pocket than theirs.

Mileage: 142035, Parts (including oil analysis kit) $70, Labor Saved: $77