Page 1: Safety Checklist
Page 2: Bosch K-jetronic
Page 3: Engine

• Oil -- The life blood of any internal combustion recipricating engine. There are a few rules to know about oils. First is to change it, every 3000 miles (or sooner if you're a weirdo like me). What you choose to put in your car is up to you. From synthetics (yes people have run synthetics on 20 year old motors, myself included) to proper weight, you'll get a million and one answers to the "oil question". The only advice I can offer is look at your shop manual, what does it say? Weight selection can differ on time of year and climate in your area. Whether you think a synthetic is worth the extra money to you is a personal choice.
• Coolant System -- Equally as important as the oiling system is the coolant system. Cooling has a dear place in my heart. I really enjoy the study of heat transfer and thermodynamics, which are both included in the cooling system of an automobile engine. I have a few personal rules that I follow when maintaining my coolant system. Just as a disclaimer, I live in Arizona where the summers reach higher than 110 degrees.
  • Water -- Water is water right? Wrong, living in Arizona we have some of the hardest water in the United States. Hard water leaves lime deposits (hard water stains in showers) on the coolant system of your car. Ever replaced a water pump and see that white crust all over the place? That is from filling your radiator with water from a hose. It sounds riddiculous and totally over the top, but I use distilled water in my engine. Distilled water is free of deposits and is the closest you can get to pure H20 without really having to pay for it. Using distilled water insures a cleaner coolant system, which translates into better heat transfer (you can not transfer heat between two materials efficiently without contact) and distilled water has a higher specific heat than tap water. Having a higher specific heat means that distilled water can absorb more of the engines heat than tap water and still remain at operating temperature (12 o'clock on the gauge). The specific heat is just an added bonus to distilled water, it should be used mostly for its purity rather than it's thermodynamic properties.
  • Thermostats -- Thermostats are bimetallic devices that control the flow of water into and out of your engine. When a certain coolant temperature is reached the T-stat opens allowing the warm liquid surrounding the engine to be replaced with the cooled coolant in the radiator. This piece is very important. The standard position for a thermostat is closed, so if it fails and does not open it will restrict coolant from leaving the water jackets of your motor. This will cause the coolant temperature to rise rapidly. If the driver is unaware of the rise in coolant temperature the car can overheat quickly, which is very detrimental to an engine. The head can warp and delicate engine components can become altered by the change in temperature. Changing a thermostat when you flush your coolant system for the summer is a quick and easy piece of insurance against this happening to you. Also, a T-stat can be selected for multiple heat ranges, meaning that if you live in a cold place you can select a thermostat that will best suit the outside atmosphere.
  • Cleaning the Radiator -- When flushing the coolant system it is a good idea to remove the radiator from the car and give it a little attention. First order of business should be to clean all the bugs and other crud that has caked onto your radiator from the car moving forward. Don't use a pressure washer, a simple stream caused by your thumb is plenty to get the crud off of the radiator. Second is to clean the inside of the radiator. If you're lucky enough to have been using distilled water than you shouldn't have to worry too much about cleaning the passages of the radiator. A good flow of water from the hose through the radiator should do fine. If you suspect blocked passages or otherwise a radiator shop in your area can service the heat exchanger for you.
• Rubber Hoses -- Critical things run through rubber lines. As I've mentioned before E21's are older automobiles and rubber doesn't last forever. Things like vacuum lines and coolant hoses can crack and break causing running problems or overheating. Inspect these rubber components on a regular basis (don't be afraid to use the hood... that's why BMW put it there). Fixing vacuum leaks can improve the cars idle and fuel economy, while replacing coolant hoses insures that the engine won't run low on coolant and overheat.
• Electrical -- The electrical system is critical to the operation of your engine as well as offers many of the ammenities we enjoy. Make sure that all the fuses in your fuse box are of the proper amperage (check the fuse box cover, or ask a forum member). Also, checking the engine harnesses for cracks or signs of abrasion (rubbing through), can help you avoid potential problems and short circuits. The fuses in these cars are the bullet type which can lose contact sometimes causing a situation (one headlight out, etc.). Before pulling apart anything electrical check the fuse for failure and contact. Giving a fuse in question a spin and trying the component controlled by it again can offer a quick solution to a sometimes daunting task.
  • Spark Plugs -- Spark plugs, like oil, are difficult things to select. Many people are diehards about which plug they will use. Let's face it, the spark plug is the only thing that is easily replaced in the car that directly effects the combustion in the chamber. The truth is you have to replace them. They are subjected to more grueling evironments than anything else in the engine. Swapping plugs every year is a VERY good idea. It's only 4 cylinders so depending on your car budget you can change them out for less than 6 dollars (USD).

    The big question is which brand? Platinum or non? What heat range? Well, I won't tell you what to put in your car, because I honestly don't know. Heat range can be selected from what your old plugs looked like, and any parts store clerk can help you figure that out. Most people select Bosch, NGK, AC Delco, or Champion. All of these are quality plugs and each company makes a set for an M10. Weither you go platinum or not is again a personal choice. I would NEVER buy a platinum plug. They supposedly last longer, but can not stand up to high voltage coils, or ignition systems with "hot rod" stuff on them (MSD's, Taylor's, etc). Copper electrodes are the best that I know of, but need to be replaced often (every year at least).

  • Batteries -- A battery is pretty important to the proper function of any car as well. Again, I live in Arizona where the heat and dry conditions destroy batteries faster than you can say "DieHard". I won't get into the debate on the stock location of the battery, but I will go into the selection process. The biggest thing about batteries is CCA (cold cranking amps). All batteries run at 12volts give or take. Amperage is what gives electrical components kick. Ever notice that speaker ratings are not done in volts? I personally run an Optima Red Top. Exspencive but probably the last battery I'll ever buy. I've seen Interstate megatron's go for long periods of time. The moral of the battery story is just like everything else with the car. The probability of being stranded is most likely in direct proportion to the number of dollars you want to save on cheap components. My car cranks over faster and harder with the optima, the stereo dims less when the bass hits (no I don't have a good stereo) and I can jump start 12 cars and then start mine. This is just me though. I don't want to be replacing a junk battery every summer.