Learn how to diagnose & repair BMW Cooling System problems:
BMPdesign will help you recognize BMW cooling system problems & issues before it is too late. The following BMW cooling system repair technical advice, recommendations, tech tips, and videos will teach you how to diagnose, and repair your BMW's damaged or worn cooling system components.
With over 30 years experience, our BMW repair videos and instructions will give you helpful tips on weaknesses that your specific model may have. Knowing this information in the beginning will save you hundreds of dollars by aiming you in the right direction before you purchase unnecessary parts. Send us a repair request!
The cooling system components are the water pump, hoses, radiator, thermostat, control valves, cooling fans, heater core, and the expansion tank. All parts in this system deteriorate more from time than use
BMW cooling systems maintain proper engine temperature by circulating super blue coolant through the engine to soak up engine heat, a radiator to cool the coolant off with air, a thermostat valve to control flow and a temperature sensor which activates the external cooling fans.
BMW Water Pump
The main water pump, keeps the coolant mixture moving.
A secondary electric water pump is used for improved flow and cooling.
The drive belt that turns it. On newer cars this is the engine's timing belt. On older cars, the pump and belt are external and run off the main crankshaft pulley with a "V" or flat belt.
BMW Coolant Hose
All hoses should be checked every 6 months for cracks, flexibility and evidence of leakage. Whenever the coolant is removed for replacement the damaged hoses should be replaced also. All hoses should be replaced when two or more are showing signs of deterioration.
BMW Radiators, Expansion Tanks, Heater Cores and Control Valves
These components are normally only replaced due to leakage or something inside restricting the coolant flow. Inspecting the condition of these parts and proper functioning is critical to many other systems within your BMW. The radiator or expansion tank cap is a spring-loaded valve reacting to system pressure. It serves to maintain proper system coolant level at predetermined pressures. It must always be replaced with an exact replacement cap with the same pressure setting.
The thermostat opens and closes based on the temperature of the coolant flowing through it. A high temperature reading followed by a drop to normal temperature, or a continuously low temperature, is common of a sticking thermostat.
BMW Cooling Fans
A belt-driven fan for pulling air through the radiator is on the water pump pulley and has a fan clutch which allows the fan to turn with the belt at low engine speeds. A bad fan clutch doesn't allow the fan to spin at low speed or doesn't allow it to spin at high speed.
An electric fan can be either by itself or used with a mechanical fan. They are controlled by a temperature sensor - in the radiator or upper radiator hose or on the thermostat or water pump housing. This sensor is commonly called an "auxilliary fan switch".
Other common temperature sensors are:
Gauge Sending Unit (variable output)
Warning Light (on/off type)
Fuel Injection Sensors (variable to control fuel injection settings)
Thermo-time Switch (cold start valve control)
Temperature control is critical to both performance and emission control. It is difficult to troubleshoot with computers that adjust timing, idle speed, vacuum and fuel delivery automatically to make up for potentially faulty temperature sensor signals.
BMW Cooling System Tips:
Keep your engine, radiator, fans and grill, as clean as possible.
Replace coolant at or before factory recommended intervals always allowing the coolant system to purge out the air before installing the radiator cap.
Replace all cooling system hoses - upper and lower radiator hoses, bypass hoses, heater hoses, manifold coolant hoses and any other hoses whenever you detect signs of deterioration or damage.
Replace the thermostat with the original temperature setting equivalent. The electronics in your vehicle may use that setting for other controls. Do not substitute under any circumstances.
Replace the radiator/expansion tank cap with the original pressure setting and OE-type equivalent.
Adjust or replace the external water pump drive belt at recommended intervals to prevent unexpected belt failure.
Replace your water pump with an OEM pump or performance pump at the first signs of trouble or when your timing belt and tensioner are replaced.
Replace the fan clutch and/or fan blade if worn out. BMW temperature gauge often can indicate if your fan clutch needs attention.
Replace temperature sensors as required by BMW experts who have the proper equipment to diagnose the failure.
Parts you should consider when working on BMW cooling systems:
Coolant BMW Water Pump BMW Thermostat Water Pump Drive Belt (timing, V-, or flat) BMW Hoses (upper & lower radiator, bypass, heater, manifold coolant, etc.) BMW Radiator Expansion Tank Heater Core Control Valves Temperature Sensors - as needed Radiator Cap and/or Expansion Tank Cap Fan Clutch
BMP Design Repair Tech Tips are added regularly. Come back often to check for new BMW Repair topics.These repair tips are designed only as a starting point. Please seek the assistance of a professional BMW mechanic for all repair problems beyond your capabilities.
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