Draining and filling your cooling system is a maintenance requirement as well as being part of many repairs. Be careful when working with coolant. It is poisonous and especially dangerous for pets. Clean all spills immediately and rinse area with water.

Working in engine compartment, remove expansion tank cap. (green arrow) Be sure engine has cooled before removing cap. Cover cap with rag when opening, if there is still system pressure, this will lessen the spillage.

Working at bottom of radiator, remove radiator cover fasteners. (green arrows) Once fasteners are removed, the metal brackets will come off. Note the position of these brackets for easier reinstallation.

Then remove cover from vehicle by pushing it toward front of vehicle to unlock tabs that lock into subframe (green arrows), then pull down and remove from vehicle. Place a 5 gallon bucket under left side of radiator.

Remove radiator drain plug and drain coolant. (green arrow) Allow coolant to drain into bucket. Once coolant has stopped dripping, reinstall radiator drain plug.

Some E90 models have two radiator drain plugs, one on the left and one on the right side (green arrow). If you have two, remove the right side after you are done draining the left side.

Working at right side under vehicle, behind sway bar, locate back of thermostat. Then remove hose by loosening hose clamp (green arrow) and pulling hose off thermostat. Allow coolant to drain into bucket. Once coolant has stopped dripping, reinstall coolant hose. Be sure hose is installed correctly and replace hose clamp if there is any doubt it isn’t in good condition. . Filling cooling system:

Using a 50% distilled water 50% engine coolant mix, slowly fill expansion tank (green arrow) until coolant level indicator reaches MAX. The level indicator diagram is located on tank (yellow arrow), reference this when filling to obtain the correct level.

Working at top of coolant expansion tank, loosen coolant expansion tank bleeder screw (green arrow). Then fill expansion tank until coolant comes out of bleeder screw. Then install and tighten bleeder screw. Bleeding cooling system: Trapped air is common when filling a cooling system and can result in improper cooling. It is important to bleed your cooling system each time the cooling system is serviced. Install expansion tank cap and be sure all bleeder screws are tight. Turn ignition ON (do not start engine), set temperature controls in vehicle interior to full warm and blower fan speed to Low. Press accelerator pedal to floor and hold down for ten seconds. Electric coolant pump will run for about 12 minutes to circulate coolant and bleed air from cooling system Once pump has run the cycle, check level of coolant in expansion tank and adjust as needed. Start and run engine at idle until it reaches operating temperature and check cooling system for leaks.

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