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Sunday, December 21, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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Tuesday, March 17, 2009

Another Day, Another CEL

I gave the car a much needed bath on Sunday and then topped off the tank in prep for the work week. Not far from my home during the commute Monday morning the Check Engine Light (CEL) illuminated again. I think it was at this point I mumbled to myself that BMW should have named that light "Check Blood Pressure", because every time it illuminates it means money will exit my wallet faster than an afterburner burns jet fuel, and if it's anything that irritates me more in a trying economy it's spending extra money that I'd just as soon put into my savings account.

(Image: Scan of GT1 fuel tank leak fault code page) Always the DIYer, however, I quickly donned my troubleshooting cap and realized that while it could be something related to the catalytic converters (again), that was pretty unlikely. Even I'm not that skeptical. So I began to think -- what else could the OBD system complain about that would not cause any rough running. Hmmm....that charcoal canister (that filters fuel tank vapors) is getting up there in age and they most certainly don't last forever. Then I asked myself the same question I ask when debugging software -- what else has changed recently? And then the light bulb came on -- I refueled. Could this be something as simple as a loose fuel cap?

Intent on remedying this with as little pain and suffering as possible I pulled over to the side of the road, threw on the flashers and dodged the oncoming traffic while I made my way to the far side of the vehicle to check the cap. And sure enough, I found the cap fully tightened but half latched (meaning, one of the tabs that locks with the filler collar was outside the collar flange). Relieved, I quickly refastened the cap, cursed the intelligence of the particle physicist / gas station attendant that filled my tank and hopped back in the car. As I pulled away I then pondered the question of whether the CEL would extinguish on its own now that the problem was corrected -- as it is known to do for other faults including those related to the catalytic converters.

Rather than hold you in suspense I'll tell you the answer is NO. A fuel system leak fault is permanent and must be cleared with appropriate diagnostic equipment. And there is no threshold with this fault -- if it happens once it will illuminate the CEL. This morning I brought the car into the dealer to have my tech pull the codes and the result was what I expected (see picture). Best of all, it didn't cost me a thing, and I even got to chat with a cute girl in the showroom while I laid on the floor under a new M3 analyzing how easy it would be to work on. I think she thought I was a little crazy. She was probably right.

Moral of the story? If you are forced to tolerate full service gas stations or are simply one of those lazy people like me who've become used to full service stations and don't want to get out of the car, just take the 30 seconds required to check the cap yourself and avoid this headache.

Mileage: 173900

Saturday, March 21, 2009

(Image: Blackstone Labs Oil Analysis for 03/26/2009 Another DIY Oil Service

I performed another oil service today, this time about 150 miles or so ahead of schedule, because I knew my schedule next weekend might be a bit crazy and because I figured it would be hard to top today's beautiful weather. The task went as expected and I reset the oil service lights with my handy-dandy clip lead tool that I use to ground pin 7 of the 20 pin diagnostic connector for three seconds.

Since I skipped the oil analysis last time and I experienced a coolant leak last month (which turned out to be nothing more than a thermostat housing), I decided to do another oil analysis. This time around I was particularly interested to learn if coolant was leaking anywhere else and finding its way into the oil, but aside from the apparent inability of the vendor to get the size of the engine correct (my engine's displacement appears to be shrinking before my very eyes) there was nothing to report. All the numbers appear to be following trend and the trend is acceptable. Based on these numbers I'll likely skip the analysis next time.

I had a couple extra quarts of oil left over from past changes where I purchased 7 quarts rather than the 6 I normally use. That helped keep the parts costs down to $30 this time around. Combined with the $25 oil analysis the total for this service came to a mere $55. And, naturally, I saved labor costs of around $100 doing this job myself.

Undercarriage Inspection & Suspension Work Research

While I was under the car I did my usual undercarriage inspection and found everything in one piece. However, given recent experience with the vehicle it is clear that I'll need to bite the bullet and do some suspension work this year, preferably before the DMV inspection comes due in September. I don't think the condition of the suspension has progressed to the point that it would actually fail inspection but I assume if I postpone the work and it does fail I'll be under the gun to get the job done within 30 days and that may force me to pay someone else to do the work. And that could get rather expensive.

I confirmed that the inner ball joint retaining nuts for the front lower control arms are 22mm. I also figured out that my special 1/2" drive pivoting head ratchet will reach the notoriously inaccessible left side nut with ease. The problem is the right side nut is too close to the engine mount to allow use of the ratchet. In lieu of that I applied a 22 mm box end wrench but discovered that I'll need to remove the sway bar to provide the clearance to swing it. That's no big deal, really, since I have to disconnect the end links from the control arms to remove them anyway.

(Image: Exploded view of the E36 rear suspension) It is now painfully obvious that the (original!) forward bushings on the rear trailing arms (item 4 in the diagram) need to be done as the rear of the car is disturbingly loose over bumps in turns, and while the aging shocks may be contributing to this problem they are not the only cause because the car did not feel this way when the last set of shocks went to greener pastures. While replacement of the forward bushings can be difficult without special tools, that is not what concerns me. With the exception of the shocks and mounts the entire rear suspension and subframe assembly is all original. If the forward trailing arm bushings are gone the upper and lower control arm bushings / ball joints (items 2, 3, 6 and 8) can't be far behind. Doing those requires more expensive special tools. Again, not impossible...just expensive.

To add insult to injury, I've learned that at least one of the inner upper control arm retaining bolts cannot be removed without sliding the differential aft a bit. In other words, this could turn into a very big job, and possibly one too big for me to handle on my own. Could I do the RTABs and call it a day? Probably. But then I'd have to pull everything apart again in short order. If you've wondered why I've put off the suspension work for the better part of two years, this is why.

Oh, and did I mention I still have the ventilation blower to install and the driver's seat to rebuild? It's going to be a fun year, that's for sure.

Mileage: 174157, Parts: $55, Labor Saved: $100