BMW Cooling System Information: Troubleshooting and Tips for older BMW Cars

The single best instrument for testing your older BMW's cooling system (radiator, fans, thermostat, water pump, hoses etc) (E9-E36,roughly) is your BMW's temperature gauge. Learning how to read and understand the temperature gauge is underrated and less common knowledge than you might guess. In southern climates, the cooling system found on older BMW's is marginal on hot, humid rush hour days when the AC is even ineffective. First off, do not open the cooling system unless the temp gauge is showing halfway or less. Avoid potentially serious burns this way. BMW Engine coolant: The best coolant for old school bimmers is 100% water. However, water freezes and rusts the engine block. The compromise is to run a 50/50 mix of antifreeze and water. Not only does the coolant mixture need to be right, but so does the coolant level. All six cylinder BMW cars have coolant/radiator expansion tanks, all but the earliest of which have a 'max' level mark indicator. No mark on your (old!) BMW? Fill it to the tank seam. You can leave the condition of your cooling system to chance and to the warning lights if your car is so equipped, but I say periodic hands on inspection is needed. Most (pre M42, ie M10 engine cars) fill directly at the radiator, making coolant level harder to figure out. Coolant MUST be higher than the top of the core and it usually ends up about halfway between the core top and radiator cap. Not sure of the level in your car? Fill the radiator to the cap, take the car for a test drive to bring the system up to operating temp, and the system will bleed itself of enough coolant necessary to create the air pocket for expansion. This gives you max amount of coolant and the space needed for hot coolant expansion. Temperature gauge needles usually hover around the midpoint on most BMW's during normal driving. Extreme outside temperature conditions vary needle positions slightly. The hotter and more humid the weather, the less efficient outside air draws heat from the radiator. This increases coolant temp, and makes the needle tick slightly upward. The engine idling for extended period in hot weather (especially with the air conditioning on!) can bring the needle to the 3/4 mark. If it is really hot out, your best bet is to shut off the AC and crank the heater fan on the lowest non AC setting to prevent the engine temperature from going into the 'red' area. To be continued: The next segment will tackle Troubleshooting and diagnosis, plus cooling system maintenance tips.

More Power For 2.7 BMW 'ETA' Cars (325e, 325es, 528e)

This article applies to all BMW M20 2.7 liter 'e' (eta) cars. Examples includes the E30 325e, 325es, and 325, plus the E28 528e. These cars with the 'lowly' eta engine be upgraded quite a bit -for fairly short money. First, you must change the rear axle gear ratio, also known as the Differential. Most ETA cars have the 2.93 open differential; some late 87-88 528e's have a 3.25 5 speed, and 3.45 auto gears. None of the modifications listed below will be nearly as effective without a differential swap (cheap and easy). Find a 3.25 or 3.73 from a 325i. 533i's anbd 535i's are commonly found with the 3.25. Junkyards are your friend. Or look on ebay, the turner motorsports BMW parts classifieds, roadfly BMW forums, or the Bimmerforums BMW parts classifieds. The next step addresses ignition and fuel. The stock control units retard the spark at certain points, and give less than ideal advance for full power. This was done by BMW to protect the engine from the possible effects of low octane gas. The stock ignition also features an annoying rpm limiter. Replacing the ECU with an aftermarket chip can do a decent job if mapped correctly. Mark D of Canada has great chips for these cars, as does Turner Motorsports/Jim Conforti. Spark advance should give a total of 33 degrees at full power with the stock (mild) cam, fuel is not a proble,. Changing pressure, rate of pressure rise, adjusting the flow meter, or changing fuel injectors can further benefit. However, dyno testing and analysis of the results should be done first. The Bosch 126 injectors that come with the e/eta engine have the capacity to support 170 horsepower (hp) at 55-60 PSI full power fuel pressure. Use a Bosch 201 injector for horsepower levesl beyond that. Some folks have used a Mustang 5.0 injector. I am not sure how well this works. Need more real world horsepower for your E car? Here are a few common 'classic' hot rod setups for the BMW M20 2.7l engine, as prescribed by Pete McHenry of Precision Performance in North Carolina: 3.25 differential, chip, stock 325i camshaft and valve springs, 5800 rev limit. 150-155 horsepower. 3.25 differential, chip, ported head, 325i valves, 325i cam, valve springs, 325i throttle body (with manifold opened to 65mm), headers, 6200 rpm limit. 165-170 hp. Same as previous setup, but utilize 3.73 differential, Holley 4160 4 barrel carb, euro 520i manifold. 323 distributor, Schrick or similar 272 degree camshaft and springs, 6300 rpm rev limit. This is the hot low buck setup right here. Serious acceleration, tq/hp... around 175 hp! 3.73 limited slip differential, ported 325i head, bigger valves with some attention to them, 288 cam, lightweight flywheel, forged steel camshaft. 325i rods, 325i overbore pistons with specially machined domes/tops, 325i intake manifold and throttle body, 323i distributor. Injection is from a 1977-1978 M30 'Big Six' L jetronic airflow meter, wiring harness, and control unit. Use 1 1/2" headers (any good headers will work) with a dual 1 3/4 or single 2 1/4 inch system. McHenry says that with good headwork, matched cam, good exhaust, this combo can make 220+ crank horspower. Not bad for a fuel economy based M20 engine that began life with a whopping 121 horsepower!