BMW E30 cooling system: overheating, bleeding and leaks
E30 overheats or the temperature gauge climbs to red – what causes it?
The most common causes are air trapped in the cooling system, a fan viscous coupling that does not engage, a stuck thermostat, a clogged radiator and the water pump. If the coolant mixes with the oil or foams, the cause may be the head gasket.
How do I check the E30 viscous coupling and radiator?
With a warm engine, the fan must not stop easily when you try to stop it by hand, and it must not spin as freely as it does when cold. To test the radiator for a blockage, remove the lower hose and pour water into the radiator: it should run out quickly.
How do I bleed the E30 cooling system?
1. Fill the expansion tank to the cold mark and set the heater to full. 2. Open the bleed screw (its location depends on the engine, e.g. on top of the thermostat housing or next to the expansion tank). 3. Start the engine and add coolant as the level drops. 4. Close the screw when only coolant comes out of it. 5. Check the level when cold.
Why does my E30 leak coolant or push it out of the overflow hose?
The expansion tank cap seal or pressure valve may be bad, and a new cap fixes it. Coolant running into the footwell points to the heater core, its pipes or connectors. Worn O-rings on the radiator drain plug can also leak.