Bleeding The Coolant System
Warning: Do not add cold water or coolant to a hot engine. Engine damage could result from the sudden change in temperature
Caution: Do not remove the coolant reservoir or radiator cap with the engine hot. Undoing either could spray hot coolant and cause burns or damage the engine
Tip: Always use a 50/50 mix of BMW coolant and ionised (or distilled) water to refill the system
- Fluid: 50% BMW anti-freeze / 50% distilled water
- M20 engine: 11 quarts
- M50 engine: 11 quarts
- M60 engine: 13 quarts
Standard Bleeding Procedure
- Switch the ignition to the second position. Do NOT start the engine
- Set the heater to 32C on both sides, fan at lowest speed (but not OFF)
- Loosen the bleed-screw (two turns)
- Pour the coolant mixture into the expansion tank. If coolant begins to overflow, fit the cap and tighten the bleed-screw, then give the upper radiator hose a few squeezes, remove the cap and loosen the bleed-screw
- Once you have at least 2.5 gallons in the system, start the engine and position the car facing up on an incline (or drive on a pair of ramps)
- With car cold, turn the key to a run position (do not start the car) and set the HVAC system to 90 degrees. The fan should be on low
- Remove the coolant pressure cap from the expansion tank and the bleeder screws from thermostat cover and expansion tank.
- Begin to pour coolant into expansion tank keeping level near the top of the tank until air free coolant flows from thermostat cover bleeder hole, install the screw and close bleeder
- Continue to fill the expansion tank until air free coolant flows from the bleeder screw on the expansion tank, you will need to keep the expansion tank filled to the top to complete this step. When no more bubbles then install and close the bleeder
- Fill coolant in the expansion tank to near top and reinstall the filler cap
- Now take the car for a 10 minute drive to warm up the engine. Get heavy footed once the engine reaches normal operating temperature. We want to stress test the system
- Park the car and let it cool down to ambient temperature (at least a couple of hours).
- Check the coolant level in the expansion tank. Repeat the bleeding process if the coolant is low or empty
- If the expansion tank refuses to hold coolant, you may have a coolant leak or damaged head gasket
- Monitor the coolant level and temperature for several drive cycles while adding coolant as needed to maintain full cold level. The coolant level should stabilize after a couple of drive cycles
Bleeding Procedure for V8 Engines
Our cars are self-bleeding. This doesn't mean that the system does not require bleeding, it means that the cooling system is easier to bleed.
Fill up the expansion tank with a 50/50 mix of BMW coolant and distilled water. Take off small line running to the top left (driver side) of the radiator. The line in question runs to the radiator nipple located above the upper radiator hose. The coolant level should start to go down, observe the smaller hose for coolant movement and air bubbles. Keep filling the coolant until the coolant flows freely sans air bubbles.
Leave the expansion cap off and start the car. Let it sit for approximately five minutes while checking the temperature gauge. Tighten the clamp securing the smaller line (i.e., bleed line) to the radiator and let the car run until the temperature needle hits the center. Squeeze both upper and lower radiator hoses multiple times to remove trapped air.
Secure the expansion tank cap and observe vehicle temperature for another 10 or so minutes.