A few words about service intervals. There's been a lot of confusion about service intervals for various BMW models. Some background, as well as specific information, on service requirements should be helpful.

Back in the 1960's, BMW's had a 4,500-mile service interval. This was increased across the board to 6,500-mile intervals for the 1970's models and to 7,500 miles for BMW's in the 1080's and early 1990's. In 1993, the service interval was increased to an unheard of 10,000-mile interval for the 740 and 840 models. The following year, 1994, the 10,000-mile interval was extended across the line. Keep in mind, your service interval light measures approximate miles and keeps track of other variables that determine when you should take your car in for a service. In earlier models, the service light is activated by an OBC that monitors the actual miles driven, your average RPMs, driving temperatures, and how much stop-and-go driving you do. Those variables, in addition to the actual mileage, determine when a specific service is appropriate. Service interval lights in more recent models monitor fuel consumption as a service interval determinant.

Personally, I recommend BMW owners not wait until the 7,500-or 10,000-mile interval to change the oil and filter. We suggest that you change the oil at half the interval. It is not required for purposes of the warranty, nor is it the factory's formal recommendation. I've found that clean oil and filters are cheap insurance in terms of preventing long-term engine problems.

Let us also talk about transmission service intervals. Automatic transmissions in BMW models prior to 1991 were initially serviced during the Inspection I service at 15,000 miles and then every 30,000 miles thereafter. With the 1992 models, automatics were first serviced as part of the Inspection II procedure beginning at 30,000 miles and at 30,000-mile intervals thereafter.

With the introduction of the A560Z transmission in the 530/540I 840I and 740I models, routine servicing of automatic transmission became a thing of the past for those models. Those transmissions are equipped with "lifetime fills."

Transmissions for 750's and 850's built prior to 1995, however, continue to require servicing. Predictably, the 750 and 850 models from 1995 and later are equipped with automatics that do not require routine servicing. What about other fluids you ask? Hydraulic fluid flushes and corrosion inspections are now performed biannually (or every 2 years) Coolant flushes are now recommended every three years, and air bag inspections are conducted every three years as well.

New Fuel Sending Units. The Z3 roadster has had very few service problems since its debut last year. However, there has been a problem in some cars with the fuel tank sending unit which causes the fuel gauge to suddenly register empty, despite how much fuel is in the tank. BMW has re-engineered the sender unit to solve the problem and your authorized BMW service dealer will install new units under the factory warranty for cars experiencing the problem.

Do your brakes squeal? Brake squeal is a common complaint we hear from time to time. There are differently styled brake pads now to eliminate the problem. On some models, BMW offers different caliper hardware to help reduce brake noise and there are certain techniques we use to solve the problem.. One of the most common procedures is for the service technician to put a 45ø beveled edge on the brake pad edges and a non-directional finish on the rotors. This alleviates the brake squeal noises in the most extreme cases. In some case, try to lightly - and I do mean lightly - depress the brake pedal for two to three seconds while continuing at your operating speed in order to clean the glaze that can build up on the surfaces of the brake pads.

Also, keep in mind, brake squeal sometimes is influenced by environmental condition - such factors as humidity, climate, temperature, etc.

Sticky Wheels? Sometimes, the wheels remain stuck to the hub even after the lug nuts are removed and have to be literally knocked off. That's due to the dissimilar metals of the wheel and hub. I don't know what other dealership service centers do, but we clean the hub centric areas and then apply an anti-seize compound to eliminate the problem.

"Clunk, clunk." Who's there? We get frequent complaints from E30 and even some E36 (1984 and later 3-series) about a "clunk" from the rear of their cars that happens when they go over a slight bump or rise. The problem is usually the rear upper shock bushings separating. The cure is to replace those bushings.

Trunk switch problem. The new 5-series model E39 has had a problem with opening trunk doors. People assume the trunk door is secured by a mechanical latch that would require a hefty push to open. That's not the case. The trunks on the new 5-series are operated by an electrical switch which does not require you apply special force to activate. In fact, that has become the problem - people punch the switch so hard that the switch mechanism becomes pushed back into the trunk area and therefore becomes inoperative. BMW has now developed a better-designed switch panel which prevents it from being pushed inside the trunk. Meanwhile, go easy on the trunk switch and shouldn't have a problem.

(Craig is service and parts director for Brecht BMW, located in the Escondido Auto Park.)Tech Talk
by Craig Hauenstein
Fahren Affairs, May 1997 San Diego BMW CCA