As the temperatures rise and the summer driving season is in full swing we have many customers towed in with overheated engines and leaky radiators. In the hotter months your BMW’s engine cooling system has to work harder to keep your engine from over heating and your air conditioner blowing cold. City driving is especially hard on BMWs as both fans have to come on high to get enough air through the radiator as you sit in traffic. If you have your air conditioner running the radiator also absorbs heat from the ac condenser that gets super hot in order to deliver cold air inside your vehicle’s cabin. All this puts tremendous strain on a engine cooling system that is under 30 pounds of pressure and mostly made out of plastic.
Modern BMW engines are all aluminum which make them lighter and flow better for more power. One unfortunate aspect of aluminum engines is that they are more sensitive to extreme temperatures and more prone to warping than older engines that were made out of iron. A single overheat can cause a blown head gasket, which will lead to more overheating. The head gasket[s] seals the head[s] against the engine block and has to be strong enough to withstand millions of combustion cycles and keep coolant passages from the engine block to the heads sealed.
The symptoms of a failed head gasket are misfires and randomly overheating engine. Head gasket replacements are quite costly as the job requires taking apart the top end of the engine. Then removing the heads and having a machine shop mill the heads to make them perfectly flat again. Finally the technician has to put everything back together which is time consuming.
As stated earlier in this post, BMW, Mercedes Benz, Land Rover, and other automobile manufacturers make their radiators out of plastic as well as other cooling system components. They have plastic hoses and plastic tanks that are under pressure and are now experiencing higher temperatures than what they are rated. Under those conditions it won’t be long before those components start to leak or outright burst.
Maintenance and repair on your cooling system isn’t too costly as long as the system is serviced in a timely manner. If the car is running hot and the warnings are ignored then problems can cascade into major repairs.