Good points Ed.  Remember that the normal coolant flow is on the order of 30 - 40 GPM.  That's a lot of water, so don't use a filter that will be too restrictive (if you must do it at all).  My evaporator cores are 1970s vintage and never changed.  I used 50-50 Preston and distilled water  for the first 3 years (no changes of coolant during that time) and Dexcool (Sp?) long life (the red stuff) and distilled water for the last 9 years.  Never any sign of corrosion or blockage in spite of the silly stories circulating about the incompatibility of Dexcool & similar long life coolants with aluminum.  I do know of several cases of blocked rads from engines that had sat around for extended periods with coolant (or plain water) in them.  Several were the 'brand new' turbo II engines obtained from various sources.
 
If you start with clean systems and use any good coolant and distilled water, there is no reason to expect corrosion.
 
Tracy

    ----- Original Message -----
    *From:* Ed Anderson <mailto:eanderson@carolina.rr.com>
    *To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
    *Sent:* Monday, February 28, 2005 7:45 AM
    *Subject:* [FlyRotary] Filterr or not to Filter: [FlyRotary] Re:
    FW: Cooling system update

    One thing to consider anytime you place a filter or screen in any
    fluid flow
    line where you might expect contamination (otherwise why put the
    filter) is
    that should the filter become clogged - then all fluid flow
    ceases.  Not to
    say a filter/screen should not be used, however, its my opinion
    that the
    source of the clogging elements should be determined forthwith
    otherwise the
    condition will simply return.

    I have not had any problems with clogging or scale etc.  I use Preston
    Antifreeze and Distilled water when I fill the coolant system.
    I am fairly certain that neither has Tracy with over 1600 hours -
    so it
    clearly does not happen as a matter of course.  Some tap water
    (Particularly
    in the western part of the country) has a high gypsum? and other scale
    producing mineral content.

    I took out the thermostat to preclude interference with coolant
    flow and
    perhaps that may contribute to more constant flow and perhaps less
    opportunity for scale to build up?  Just a thought.

    Ed A


    ----- Original Message -----
    From: "Paul" <sqpilot@bellsouth.net <mailto:sqpilot@bellsouth.net>>
    To: "Rotary motors in aircraft" <flyrotary@lancaironline.net
    <mailto:flyrotary@lancaironline.net>>
    Sent: Monday, February 28, 2005 7:30 AM
    Subject: [FlyRotary] Re: FW: Cooling system update


    > Good idea. Unfortunately, I have all Stainless hose with AN
    fittings.
    Would
    > like to see one with male/female -16 AN fittings that could be
    placed
    > in-line.  For those who are considering rubber radiator hoses,
    however
    this
    > would be a nice to have item. Paul Conner
    >