Flush the Cooling System

Flushing the coolant in your vehicle's cooling system is a great step in maintaining a healthy engine. A failure in the cooling system can easily result in an engine damaged beyond repair and a wallet much, much lighter. Luckily, servicing a car's cooling system is easily within the grasp of the backyard mechanic.


There are several methods for flushing a car's cooling system, each with their own strengths and weaknesses. Make sure you fully understand which steps you need to take to service your particular car.

Not Too Hot. Not Too Cold.
The engine in your car or truck runs best when it is at its optimum operating temperature. Too hot and you risk damaging or destroying your engine. Too cold and the engine performs inefficiently. Before you service your car's cooling system, it would be wise to understand how it basically works. Read this short article, then continue on with the cooling system flush procedure.

What Kind of Coolant Do I Need? Times have changed and the number of coolant colors and types to choose from have as well. Here is a concise and hopefully enlightening article on coolants.

Coolant System Flush Methods are numerous, but I am going to divide them into three main groups:
  1. Drain and Fill
  2. Flush and Fill
  3. Flushing Kit

Drain and Fill
The drain and fill procedure is perhaps the easiest and fastest method of replacing the antifreeze in your cooling system. There are only three basic steps to this method:
  1. Drain radiator
  2. Fill radiator with water and run engine for 15 minutes
  3. Drain radiator and fill with 50/50 mix of antifreeze and water
The drain and fill procedure works well if your vehicle's cooling system is in good shape. This procedure is quick and requires a minimum of tools to perform, however, your cooling system does not get flushed as well as in the other two methods.

Flush and Fill
The flush and fill procedure is probably the most time consuming of the three methods. Its basic steps are:
  1. Drain radiator
  2. Flush radiator
  3. Flush heater core
  4. Flush coolant recovery tank
  5. Fill cooling system with a 50/50 mix of antifreeze and distilled water
  6. Purge air from cooling system
  7. Top off cooling system with a 50/50 mix of antifreeze and distilled water
The main benefit of this flushing method is that the radiator, heater core and the reservoir tank are flushed. This procedure does take more time than a simple drain and refill and, unless you drain the old coolant from the engine block or combine the drain and fill procedure with this method, there will still be a little old antifreeze left in the cooling system.

Flushing Kit
Inexpensive cooling system flushing kits can be purchased an any auto parts store. These kits let you thoroughly flush the old antifreeze out of the system. The basic steps to using them are:
  1. Install flushing 'T' cap (requires cutting heater inlet hose)
  2. Backflush the system with water
  3. Add proper amount of antifreeze to attain a 50/50 mix of antifreeze and water
Using the flushing kit will allow you to very thoroughly flush the entire cooling system, however it has two main drawbacks, first, the water in the system will be tap water from your garden hose and second, to install the backflush 'T' cap, you must cut the heater inlet hose, leaving one additional spot for a leak to sprout.

Choose Your Method
Having trouble deciding which cooling system service method to use? Here are a few tips:
  • Check the condition of the antifreeze in your car by removing the radiator cap and looking inside the radiator. You can also look inside the coolant recovery reservoir. If you see rust or scale deposits or if the coolant is discolored, you should choose one of the flushing methods.
  • If your car or truck is less than two or three years old or if your vehicle's cooling system was serviced regularly and on schedule, you can probably save yourself the hassle of flushing and do a drain and refill.
  • If any part or component of the cooling system needs to be replaced (including but not limited to the radiator, any of the hoses, water pump, or heater core) you should choose a flushing method.

2 comments:

Rhino Pk May 26, 2016 at 11:12 PM  

I will go with your advice. Thank you very much for your quick response. I should also say that this is a great blog.
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jose palmer September 9, 2017 at 5:21 AM  

yes this is so great and informative article this article is help me a lot.
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