What are the reasons for the BMW 7 Series engine overheating?
4 Answers
Reasons for the BMW 7 Series engine overheating: Component damage: The cooling system is a comprehensive system, and the failure of any component can affect heat dissipation. For example, if the water pump, thermostat, fan, etc., are damaged, the cooling capacity will naturally decrease, leading to an increase in engine temperature. Unqualified coolant: Coolant is key to achieving heat dissipation. If the coolant does not meet the car's cooling requirements or cannot adapt to the local temperature environment, with a boiling point that is too low, the engine will naturally overheat. Another scenario is when the coolant has not been replaced for a long time, causing its effective components to deteriorate or evaporate, thereby reducing the coolant's performance. Cooling system blockage: The cooling system consists of multiple cycles. If there are too many impurities in the antifreeze or if the pipes are corroded due to deterioration, it may lead to a blockage in the cooling system, reducing its heat dissipation capacity.
Last time I drove an old 730, I encountered a coolant temperature warning. It turned out to be a stuck thermostat. This thing is like the engine's temperature regulator—if it gets stuck in the closed position, the coolant can't circulate properly. I remember the technician at the 4S shop said turbocharged cars are especially prone to accumulating fluff in the radiator gaps, like putting a mask on the car and making it hard to breathe. When washing the car, it's best to ask the mechanic to use an air gun to blow out the front grille of the radiator. After parking, listen to see if the electric fan is still running. Once, my friend's car had a minor leak at a small hose connector—it didn’t look serious, but it slowly drained all the antifreeze.
Clogged radiators are easily overlooked! I once helped a buddy from the car club with an inspection—his radiator hadn't been cleaned in 60,000 km, and the cooling fins were clogged like a sieve. BMW's cooling systems are incredibly complex, with turbochargers hitting 900°C, all relying on coolant circulation. During checks, first inspect the auxiliary reservoir level—remember to open the cap when the engine is cold to avoid burns. If you notice erratic temperature fluctuations, it's likely due to corroded water pump impellers. These aluminum impellers weaken like biscuits after five or six years in coolant, so I recommend changing the coolant every four years—don't fall for the 'lifetime maintenance-free' claims.
Experienced drivers know to check the electric fan resistor. One summer, I was stuck on the highway watching the temperature gauge climb into the red zone. Later, I found out the fan module had burned out—this component is located under the car and is particularly prone to water splashes. Actually, after daily parking, don't turn off the engine immediately; let the turbo cooling system run for an extra two minutes. The trickiest situation I've encountered was a blown head gasket, with oil streaks floating in the coolant and white smoke billowing out. In such cases, you must shut off the engine immediately—continuing to drive could cause the crankshaft to seize.
