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BMW and MINI DIY Video – Coolant Flush, Replacement – How To

September 28, 2012

Our BMW and MINI cooling systems have the thankless task of dissipating the heat generated by our engines (and automatic transmissions), keeping them at an optimal operating temperature; not too hot, not too cool.  In addition, the cooling system must keep corrosion and sediment from attacking the metal, plastic and rubber parts of the systems.  Like the engine’s lubrication system (oiling), the cooling system must function mile after mile and hour after hour for hundreds of thousands of miles and thousands of hours.  Faults within either of these systems will typically result in catastrophic failure and potentially terminal engine damage.  With these thoughts in mind, we can begin to understand why regular maintenance of the engine’s cooling system is just as (or more) important as the other regular maintenance tasks that we perform on our BMWs and MINIs.

We recommend a coolant flush every two to three years if using the BMW/MINI coolant and distilled water (more often if other coolant or “tap” water is used).  While the base Ethylene Glycol (EG) Antifreeze/Coolant (basically) holds its antifreeze properties for a very long time, the additives for corrosion protection, lubrication, etc, do not.  The recommended 2-year interval is due to the Silicate anti-corrosion additives that are “used up” and begin to drop out of solution after about two years of service.  When this happens, silicate build-up can happen within the radiator, heater core and engine passages.

When adding coolant, between flushes, always add the same coolant as the original fill.  While adding a common green, orange, yellow or other, coolant (which have differing additive packages and base pH) will not immediately destroy your engine or cooling system, it will reduce the effectiveness of both the base and the added coolants.  This will, at least, greatly reduce the service life or, at worst, start a corrosive cycle.

We mix the coolant with the distilled water in a 50/50 ratio.  Using distilled water for your 50/50 mix is not specifically required, but in doing so, your coolant mixture will be much more stable and far less corrosive in the long term.  This is due to the absence of the minerals and impurities that are removed in the distillation process.  These impurities encourage electrolytic corrosion to the engine block, cylinder head, hoses and gaskets, damaging these parts and causing failures and need for repairs.

The coolant flush is not especially difficult, but it does require more than simply removing the radiator drain plug.  In our DIY example (02 X5 3.0i), we’ll show the specific steps to properly drain and flush the system, then fill and bleed with new 50/50 mix of distilled water and coolant.  Watch the video (above) and see the parts and tools used, below.  For further assistance, please contact our agents at 800-535-2002 or visit our online store at

Parts Used:

BMW Coolant:

Distilled water (local grocery store)

Tools Used:

Floor jack and jack-stands, ramps or vehicle lift
Metric 3/8” drive socket set (8mm thru 17mm)
Metric combination wrench set (8mm through 17mm)
Flat head screwdrivers
Phillips head screwdrivers
6mm flexible hose clamp driver:


Spill-Free Coolant Funnel:

Garage Guard Absorbent Mat:

Coolant drain pan:

Bentley repair manuals:


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  1. Doug Ehmann permalink

    Do you sell the great yellow funnel system we saw in your video ‘BMW and MINI DIY Video – Coolant Flush, Replacement’? I don’t find it in your print or on-line catalog.

    Your DIY’s are extremely helpful. And very well done. THANKS!

  2. Steve Wu permalink

    Do you recommend a new crush washer for the engine block drain plug? If so, do you have a link to one on your site (E46 325).

  3. Chuck Kremer permalink

    Love the vid, but if I’m using Evans, how do you get out that last 2 quarts of water before I fill?


    • Otto permalink

      Evans says that you can have up to 5% water left in the system (as long as it is distilled water). You can disconnect any hoses and fittings that you can readily access in order to evacuate as mush water as possible. The 100% “proper” way to do this fluid change over is to use the Evans Pre-Flush fluid instead of water. They also state that you can use the Dex-Cool coolant for the pre-flush. Using the pre-flush (Evans or Dex-Cool) assures that there is no water in the system

      • Chuck Kremer permalink

        Marvelous… Thanks…

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