Tuesday, August 4, 2009

Radiator Flush – Antifreeze Replacement Coolant Flush or Replacing the Engine Coolant?

First it should be noted that coolant and antifreeze are the same thing. Replacing the vehicles engine coolant is part of a routine vehicle maintenance regiment, but how often should the coolant be replaced? Many auto shops will recommend a flush instead of a straight coolant replacement. What’s better for the vehicle, replacing the coolant or flushing the radiator? Find out the answer to the question, radiator flush or engine coolant replacement.

How Often Should the Engine Coolant Be Replaced?

The best answer to the question of how often engine coolant should be replaced is to find out what the vehicle manufacturer recommends. The vehicles owner’s manual should have a maintenance schedule that shows what mileage intervals the engine coolant should be replaced. If the vehicles owner’s manual is missing, the dealer or the manufacturers website should have the needed information.

Older vehicles usually require that the engine/radiator coolant be replaced every 30,000 miles. Most new vehicles from 2003 and up have a gold coolant (older vehicles green coolant) that should last up to 100,000 miles. The manufacturers maintenance schedule will have the mileage intervals required. It’s important to note that most manufacturers do not recommend a coolant flush but simply recommend replacing the engine coolant.

Drain and Refill Radiator Coolant or Cooling System Flush

Drain and Refill

  1. With a radiator coolant drain and refill the coolant is simply drained from the radiator and refilled. Most radiators have a drain on the bottom of the radiator called a petcock. The petcock is simply turned and the coolant will drain from the petcock. If there is no petcock, the bottom radiator hose can be removed to drain the coolant.
  2. After the radiator is drained, close the petcock and refill the radiator, usually with a mixture of half water and half coolant. Auto parts stores usually have straight coolant or containers that are premixed with water. Make sure the correct coolant is used to refill the radiator. If the vehicle is equipped with a coolant recovery tank, make sure the tank is at the level indicated on the tank.

Cooling System Flush

When the vehicles radiator is drained, most of the coolant in the engine remains. With a cooling system flush auto shops will either manually flush the cooling system or use a flush machine.

  • Manual Flush – When the cooling system is flushed manually, a flush solution is poured into the radiator. The cars engine is then ran until it reaches operating temperature. This allows the thermostat to open and coolant to run through the entire cooling system. The radiator is then drained and refilled with coolant. Old coolant will still remain in the engine.
  • Coolant Flush Machine – With a flush machine the coolant is forced through the cooling system and virtually all of the old coolant is removed from the cooling system. With a simple drain and refill a lot of rust and other contaminants remain in the engine. With a manual flush more contaminants are removed but some still remain.

Other Chemicals Used With a Cooling System Flush

Naturally a flush cleaning agent should be used when a coolant flush is performed. Some other chemicals that might be used may included the following:

  • Chemical Flush – Cleans the cooling systems and removes rust, other contaminants and deposits
  • Lubrication – Sometimes auto repair shops will use a lubricant that lubricates the water pump and other components to help increase the life of those components.
  • Sealants - Some experts say that a cooling system flush may break loose contaminants that may cause leaks. As a precaution they may add sealants that will actually work to seal leaks before they occur.

Whatever choice is made between a drain and refill or a flush, there are some experts that claim that a flush machine may cause more damage by breaking loose components. If a cooling system flush is performed, it’s best to make sure that there is a guarantee or warranty against future problems like coolant leaks. Most repair orders that are signed by the vehicle owner at the auto repair shop state that no expressed warranties apply. If there is a warranty, make sure that the warranty is in writing.


  1. What a nice blog you have..thanks for all this information

  2. Dont forget, always go back to the same color coolant that came out of your coolant system.