Breaking down the BMW 3 Series

The BMW 3 Series often is an entry for consumers and can be your entry to service.

BMW 3 Series BMW service servicing imports repair shop training technician training A/C training automotive aftermarket The word "European" often sends shudders down the spines of independent repair shop owners and technicians. Many shops avoid doing business with owners of European vehicles, and they all have their reasons. In some cases, a bad experience with an attempted repair has them spooked. With others, the learning curve is steep enough that it's just easier dealing with domestic and Asian brands. Many also would say that there aren't enough of these cars around to justify the effort and expense to tool up for them.

If your shop doesn't do European service and has more than enough business to get by, this article likely will not be particularly helpful. However, if you need more cars in your bays, you might consider offering service on the BMW 3 Series. The 3 Series is considered to be the "entry-level" BMW, offering the owner prestige at a much lower price tag. In turn, there are many more of these on the road than other BMW models, and thus could give your shop's revenues a solid shot in the arm. If this sounds attractive to you, read on!

The BMW 3 Series first was released in 1975 and was introduced to American roads in 1977. It was an immediate success, as it came close to doubling BMW's worldwide sales in three years. Numerous awards further validated its success, including being on Car and Driver's annual Ten Best list a total of 19 times (and counting). Apparently the automotive world has been impressed with these cars and their owners are loyal. While loyal owners can be fussy, they usually want their cars fixed right and are willing to pay good money to get it done. With this in mind, let's look at some tips and tricks that can get you started on BMW 3 Series service. This article will focus on the 1999-2006 models of these cars, which include the 325Ci/i/xi, 328Ci/i/xi and 330Ci/i/xi.

First Steps

OK, so how do we get from here to there? Obviously, becoming comfortable with BMW service will require some education, and the best place to start is with service information. Nothing is more frustrating than trying to interpret service information that is filled with unfamiliar acronyms. Very few of BMW's acronyms are similar to those used on domestic brands. In some cases, the acronym is based on an English term and can be interpreted without too much difficulty.

For example, DME stands for Digital Motor Electronics, which is BMW's term for PCM or ECM. In other cases, however, the acronym is derived from a German term and seems to have no connection to the component or system in question. An example of this is IHKA, which refers to BMW's electronic HVAC control system. These can stop you dead in your tracks, unless you arm yourself with a dictionary.

The good news is that many service information sources (like Alldata) provide a list of BMW acronyms and their meanings. My recommendation is that you find this list and print it out for easy reference as you make your way through the relevant service information.

Basic Service

Simple service such as an oil change is just a little bit different with BMW. While cartridge-type oil filters are starting to reappear on domestic vehicles, these have been used on BMWs for decades. This system is cleaner and often easier to service than many spin-on filter installations, because the housing is located on top of the engine for easy access.

When doing an oil change, start with the car on the ground and loosen the oil filter housing cover one to two turns with a socket (not a flat wrench). At this point, oil in the housing will drain to the oil pan and the car can be lifted. Drain the oil pan and replace the seal on the drain plug before reinstalling it. Torque the oil pan drain plug properly, and then lower the car. At this point, remove the oil filter housing cover and replace the cartridge along with the O-rings that came in the filter kit. Lightly lubricate the O-rings with engine oil and gently install the oil filter housing cover with a socket.

Install the specified amount of motor oil and start the car, being sure to check for leaks. Run the engine until the oil indicator lamp goes out, then shut it off. Wait five minutes, then check the oil level and add oil if necessary.

Note: Be absolutely sure to install the correct oil as specified by BMW.

Ignition Woes

A major weak point on BMW vehicles has been the pencil-type coils used in the coil-on-plug ignition system. These show up as intermittent misfires and usually cause a misfire DTC (P0301, P0305, etc.) to be logged along with illumination of the MIL. The repair involves replacing the faulty coil(s), but these can be very difficult to get at, especially on the rear cylinders of the inline six motor. In the case of the 3 Series, it is possible to remove the cabin filter plenum in the engine compartment to create more room to maneuver. This can make it easier to perform other service as well, including spark plugs and valve cover gaskets.

Start by removing the cabin filter cover and taking out the filter element. This will expose four screws that hold the cabin filter housing to the cowl. Remove the four screws and disconnect the attached electrical harness from the plenum, leaving the harness to lie across the top of the motor. With the plenum removed from the engine compartment, there is now a lot more room to get your work done.

Cooling System Service

BMW uses a lot of plastic in their cooling systems. This works fine under most circumstances, but severe overheating can cause serious damage to the system. BMW has a TSB that outlines a procedure to follow in case of an overheat, and this involves looking for evidence of melted cooling system components. If inspection reveals melted plastic in the coolant pipe under the intake manifold, almost all of the plastic cooling system lines and components will have to be replaced.

One item that could get overlooked here is the plastic impeller on the water pump. Be sure to remove the water pump and inspect the impeller for damage, as it is not unheard of for these to melt or break. A sure sign of a damaged impeller is a quick rise on the coolant temperature gauge, but no heat in the cabin.

To refill the cooling system, start by turning the ignition to the RUN position and then setting the heating controller to maximum. Set the fan to the low setting to open the heating control valves. Open the vent plug and pour the coolant slowly into the expansion tank, closing the vent when the bubbles stop. Continue filling until the expansion tank is full and replace the cap on the tank. Start the engine, running it until the thermostat opens. The engine should be allowed to cool before doing a final check on coolant level.

Even when carefully following the above procedure, it is still possible to get air trapped in the cooling system. You can save yourself a bunch of time and trouble by using an airlift tool to refill the system. BMW recommends this method and has a special tool for doing it, but a generic tool should work fine. As a final note, be certain to follow BMW recommendations regarding the coolant used to service the car.

HVAC Issues

A common concern with BMW 3 Series vehicles (especially in hotter climates) is an inoperative blower motor. The electronically-controlled versions of the 3 Series use a module on the ground side of the blower motor to control its speed. More often than not, the problem is caused by a failure of this module, which then must be replaced. BMW calls this module the "final stage," where most domestic technicians would refer to it as a blower driver module. To add to the confusion, the final stage is controlled by what BMW calls the IHKA blower control.

From a design perspective, this system is not that much different from the electronic automatic temperature control systems found on many domestic vehicles. However, a domestic technician reading the BMW service information would be completely confused and likely would swear that he would never work on another BMW. The key here is to keep a cool head and slowly work your way through the acronyms, keeping in mind that the system itself is not much different from the ones you are already familiar with.

Parting Advice

Be very careful when ordering electrical parts for BMWs. It is easy to have a misunderstanding that results in the wrong part being delivered, and it is likely you won't be able to return it for credit. Before you call the dealer's parts counter, be absolutely sure to have both the year and model number (the number on the trunk) as well as the last seven digits of the VIN. This will help the parts guys immensely and may make you a friend.

Yes, there is a learning curve with BMW service, but with patience and perseverance you could carve out a new niche for your automotive service business. Good luck with your work on the BMW 3 Series!

Tony Martin is an associate professor of automotive technology at the University of Alaska Southeast in Juneau, Alaska. He holds Canadian Interprovincial status as a Journeyman Heavy Duty Equipment Mechanic. He also has 19 ASE certifications, including CMAT, CMTT, L1 and L2.