Preparing for the Fall (or Any Other) Driving Season

These notes actually apply all year long, as today’s high-pressure, high-temperature cooling systems operate under high internal stress even in winter. The extra thermal loads of the hot days of summer and autumn driving just add a bit to their heavy job.

In the old days, all antifreeze was basically the same (green “Prestone” type), and most cooling system components were made of metal—all except the rubber hoses. The radiators had brass expansion tanks and copper-finned cooling tubes; all the basic components (water pump, thermostat, pulleys) were made of metal. Radiators could be “rodded out” or even “re-cored” to extend their lives. Typical internal temperatures were around 180°F and pressure was limited to about 15 pounds.

This all began to change in the 1980’s with the impact of emission controls: engines needed to warm up faster and sustain higher temperatures for more efficient combustion. Cost controls imposed an ever-increasing amount of plastic in place of metal. Water pumps acquired plastic impellers, thermostats became electronically regulated devices housed in plastic, and radiators and their attachments became recycled plastic and aluminum. All of these components are designed to be replaced, rather than “reconditioned.” The days of re-cored radiators and rebuilt water pumps are over. At the same time, operating temperatures rose to 240°F and pressures to 29 psi. More plastic, but also more stress.

Here are some tips for dealing with these newer cooling systems.
If observed, these systems will have a happy, extended life, and so will the car.

• Always use the blue-colored BMW/Mini coolant, and mix it 50/50 with soft or distilled water.
  Cooling systems should be drained and refilled every two years. This coolant, one of four color-coded types, is “organic acid technology.” Not easy to find at parts stores, you can obtain it at H&B or any BMW or Mini dealer
• Keep an eye on the flat, ribbed “serpentine” engine belts and their tensioners.
  These belts are usually good for 50,000-60,000 miles, but can shred suddenly if not checked during services. They show a tell-tale segmentation of the ribs on the inside surface just before they let go. Unlike the old, skinny “V” belts, these newer type can tangle up in the fan blades and wreak havoc when they break, so it’s important to replace them ahead of time. While they’re off is a good time to check the plastic tensioner pulleys. These look rather like plastic roller skate wheels, and have ball bearings which eventually wear out. When they do, they can fly off the engine and cause the same damage as shredding belts. If you hear a metallic squeaking sound, especially during the first few seconds after starting, this could be from worn tensioner pulley bearings.
• The plastic components should be replaced sometime between 8 years/80,000 miles and 10 years/100,000 miles.
  The parts typically include the radiator, its plastic expansion tank, the front engine hoses (which have plastic joints and fittings), the plastic-housed thermostat, and the plastic-vaned water pump. When available, H&B installs a stainless-steel-vaned water pump.
• Always treat coolant loss, and especially overheating, seriously.
  If in doubt, stop the car and have it towed. We have seen numerous instances of serious engine damage caused by not being alert to the seriousness of this issue. You do not want to find out how much a replacement engine for your BMW or Mini costs.