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Flushing The Cooling System.. Is it really Necessary every 25k

The truth about flushing the cooling system. When is it really necessary...
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  • edited March 2011
    Your owner's manual will tell you.

    There is no standard that covers all cars. Designs vary. Coolant varies.

    I can tell you that it is very cheap insurance. Pay a little bit now or a whole lot more later.

    Follow the manufacturer's recommended maintenance schedule. Not following it is one of those penny-wise, pound foolish sorts of things. Allowing other people (like auto shops) to tell you what to do is a good way to get taken every time you have your oil changed.
  • edited March 2011
    It depends on the car, and how well it is cared for. Personally, I replace my coolant every 2-3 years. I alternate between flushing the system and just draining-and-refilling.

    When I flush-and-fill, I flush the system with clean water. Chemical flushes are generally a last ditch effort to make due with a neglected cooling system. If you are considering a chemical flush, you might be better off simply fixing whatever is wrong, if anything.
  • edited March 2011
    Your owner's manual will tell you when it's "really" needed. Personally, I change my coolant every 2-3 years. It's cheap insurance. Cheap compared to having to deal with a neglected cooling system, which can mean at best having to replace a clogged radiator or heater core or at worst having to replace the engine.
  • edited March 2011
    It depends on your antifreeze type. Our newest GM car that uses Dex-Cool specifies 5 years, 150,000 miles max to antifreeze change. I adhered to that schedule with our last GM car that used Dex-Cool and had no problem for the 13 years that we owned the car. The 5 year limits happened first.

    For the same car, the owner's manual also specifies 30,000 miles or 24 months max if you use conventional antifreeze.

    For our older car that uses conventional antifreeze, I do a partial drain every two years; drain whatever comes out from the lower radiator hose connection and replace that with fresh antifreeze. The original radiator is still good after 20 years and well in excess of 200,000 miles.
  • edited March 2011
    When you say "flush", it covers a range of procedures. Generally a "drain and refill" is not classified as a flush, and there are two of those, one where you just drain the radiator and one where you drain the complete cooling system.

    Flush can mean that the vehicle is hooked up to a flush machine. These might also be called a reverse flush as the machine may force the coolant backward through the coolant system to dislodge anything that might create a blockage. I don't see any harm in this type of flush, but I think it is unnecessary in most cases.

    A flush done in the driveway probably denotes where the system is fully or partially drained and then water is forced through the system with a garden hose. Some people use an adapter that is permanently spliced into a heater hose, others just push the hose into the radiator. The adapter does reverse flush the radiator. The only harm I see in this is that the tap water may have some minerals that could build up in the coolant passages of the engine and radiator. Also, you will never get 100% of it back out so it could dilute the antifreeze some.

    Another version is to put a chemical such as "Super Flush" into the radiator, then allow it to circulate for a specified time, then drain, flush out with a garden hose and finally refill with fresh coolant. The disadvantage again is that you may not get all the chemical out and it is very hard on the cooling system. I personally have had some very bad experiences with this kind of flush and would not recommend it under any circumstance.

    If you follow the manufacturers recommendation listed in your owners manual for changing the coolant, that is a simple drain and refill, you will never need any type of flush. Once you are past the warrantee period and if you use a long life coolant, you can extend the drain period to 5 years or 150k miles. The new extended life coolants are very good coolants, far superior to the old "green stuff".

    Personally, I use the extended life coolants and have used them beyond the 5 year recommendation, well beyond, so I believe they have plenty of buffer built into their drain interval recommendation. I don't recommend that anyone else go beyond those recommendations because I don't wish to take responsibility if something goes wrong in their vehicle.
  • edited March 2011
    "Flushing The Cooling System.. Is it really Necessary every 25k??"

    Where did you get the 25K miles figure? Many motorists would be changing it every year, not necessary...4 years, 50,000 miles is about right for most cars..
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