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Friday, December 19, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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Sunday, October 11, 2009

Oil Service

(Image: Blackstone Labs oil analysis report from October 20, 2009)A couple weeks ago a review of my maintenance schedule spreadsheet indicated 4500 miles had passed and it was time for another oil change. Last weekend I accomplished the service with only one snag.

When I pulled the copper sealing ring from the filter kit packaging I noticed it was oblong rather than circular so I knew it wouldn't fit over the drain plug. This was obviously due to a manufacturing defect but not one important enough to cancel the oil service. The solution was easy enough -- reuse of the existing sealing ring along with judicious use of the torque wrench to achieve the usual 18 foot-pounds.

Last time I decided to skip the oil analysis so I took another sample this time around. As you can see, the report indicated slightly higher lead, which is found in bearings. That sounds bad, but I agree with the analysis. 3 PPM is in the noise, so to speak, and I consider this an uneventful report. However, as is normal practice with any oil analysis program, I do plan to follow up with another sample at the next oil service to put the issue to bed.

Mileage: 183183, Parts: $45, Labor Saved: $100


My spreadsheet also kindly informed me that the vehicle had not only passed the 30K interval recommended by BMW for the engine air filter but the 15K interval for the microfilter as well, so I picked up the $70 worth of parts from my local dealer earlier in the week and accomplished that work today.

The engine filter replacement has always been a no-brainer on this car so it's not really worth mentioning, except to say that if I had the dealer do it I would have likely spent another $36 in labor.

I have the procedure to replace the microfilter down to a science so it took only 10 minutes to complete, including a thorough cleaning / vacuuming of the airbox. Not a bad investment for a labor savings $72.

Mileage: 183475, Parts: $70, Labor Saved: $108

Wednesday, October 14, 2009

How NOT to Fix a Flat

As you may recall, back in June I suffered a flat tire and had it repaired. Unfortunately, during my routine tire pressure check last Sunday, I found the very same tire down to 24 PSI. I carefully surveyed the tire and found no obvious damage so I quickly concluded that the patch was leaking.

Given that I hadn't checked pressures in a few weeks I figured it was a slow leak and I could save myself the trouble of an "in the field" tire swap and wait until after I installed the winter tires in a few weeks to bring the tire to the shop for repair. I pumped the tire up a few pounds over the norm for good measure, resolved to check it regularly and get on with my life. When I arrived at work the next morning I looked back at the car and quickly noticed a conspicuous bulge in the sidewall. I let out a choice word and then took a pressure reading of 19 PSI, or a drop of almost 20 PSI overnight. I didn't have a means to pump the tire up in the field so I resolved to swap the tire with the spare over lunch.

This morning I took the flat back to the same company that "fixed" it last time. The guy I spoke to took a defensive posture and attempted to convince me that they did not, in fact, fix the tire last time. After I told him I don't make a habit of going around to tire shops and requesting free services he relented, but only long enough to suggest that it might be due to the valve stem. I acknowledged that might be a possibility but suggested he dunk the tire in the tank so we could both stop guessing. He rolled the tire away only to come back a couple minutes later and admit that the patch was leaking. I asked him to fix it properly this time by dismounting the tire, applying a patch from the inside of the tire, and then remounting & balancing the tire on the road force balancing equipment. He agreed to have it done later in the morning and I left for work.

At this point you might be thinking, how does a plug patch leak? Well, this wasn't a plug patch. More precisely this was what they call in the industry a "gummy string" which is the easiest / quickest repair technique available because it doesn't require dismounting the tire. This explains why they charged me "only" $10. Some research online suggested that gummy strings work in general but the failure rate is high enough to question their use, particularly on a high performance car where a sudden loss of pressure or blowout in a high speed turn could very easily result in loss of the vehicle.

Later in the day I went back to pick up the repaired tire and figured the worst of the day was behind me. Wrong. As I picked up the tire to put it in the trunk I realized the the tire machine retainer clamp had gouged a circular scratch through the clear and into the base coat of the wheel a few inches from the hub. I'll spare you the details of the verbal exchange that followed, but it suffices to say that I have no intentions of doing further business with this facility.

So what have I learned? Plenty.

Mileage: 183525