Engineering Explained - How To Change The Coolant In Your Car

Short Summary

Main recommendation: Change your car's engine coolant yourself as a preventative maintenance task, following the process shown: drain the radiator and engine, refill with a 50/50 anti-freeze mix, then purge all air from the system. The presenter, working on a 1999 Acura Integra whose service manual calls for replacement every 45,000 miles, says the job is simple and inexpensive, costing $27.37 in total.

Key Points

• The engine coolant is replaced on a 45,000-mile interval according to the service manual for the 1999 Acura Integra used in the video.
• The job should only be started once the engine and radiator have completely cooled down, which is often indicated by a warning on the radiator cap.
• Air purging is the most time-consuming part, since a cooling system can take a surprisingly long time to clear all air; the presenter says 30 minutes is not unreasonable.
• The total DIY cost was $27.37, including two gallons of coolant and thread sealant, and most tools may already be on hand.

Details Worth Noting

• Concrete instructions:
  • Set the temperature control to maximum heat. On modern cars with electronic controls, run the car or turn the ignition on first so the heater core opens fully, ensuring all coolant is replaced.
  • Wait until the engine and radiator are completely cool before working on the system.
  • Remove the radiator cap and rest it on top so contaminants don't fall in.
  • Place a container under the radiator and loosen the radiator drain plug, located at the bottom on the left or right side. Let the coolant drain.
  • Move the catch pan under the engine and remove the engine drain bolt to drain coolant trapped in the engine block and heater core.
  • When reinstalling the engine drain bolt, apply high-temperature thread sealant to the threads and replace the washer. On the presenter's vehicle, tighten it to 58 pound-feet, but check your owner's manual for your car's value.
  • Tighten the engine drain bolt first, then tighten the radiator drain plug.
  • Remove the coolant reservoir, drain it, clean the inside, and reinstall it.
  • Add coolant to the radiator until it reaches the base of the filler neck. The presenter's car takes 4.4 liters.
  • Start the engine, let it idle outdoors for about 30 minutes, and wait for the radiator fan to come on at least twice.
  • While it runs, add coolant as needed and check for leaks.
  • Once air is purged, fully tighten the radiator cap, run the engine again, and check for leaks. If none appear, the job is complete.
• The presenter notes that cooling system designs are challenging largely because of air purging, drawing on prior experience working on such designs.
• Tools are needed in addition to the parts, but many are likely already owned; the torque wrench can be borrowed through AutoZone's Loaner Tool program.

Bottom Line

Coolant replacement is a manageable DIY job at roughly $27 in parts, with patience during the air-bleeding stage being the key to success.