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In recent topics here about water pumps, changing coolant and coolant types,two things/questions came to mind:

# How often? The makers of the long life coolants If I remember right are saying something like "five years or 100,000 miles."

# In my cars if changing I usually run a can of radiator flush thru before, run engine hot for ten minutes, drain, flush with distiled water, then refill with the coolant-distilled water mix.
But with the Rotax 912 not having the same convenient easy-opendrain valve at lowest point of cooling system as the car does on the radiator, etc.,that procedure (the several drain, warm up,and refill operations) would be a bit of a PITA.
So my question is, is the flush-cleaner additive step recommended strongly, mildly, not-at-all, or perhaps even frowned on?
For what it' shorthand, our old coolant although 2+ years old looks perfectly crystal clean and normal color..... To me suggesting a cleaner-flush additive step is not necessary.

Opinions from you more Rotax experienced folks?

Al
  • Re: Radiator flush before replacing coolant?

    by » 11 years ago


    I'm sure this topic will get several answers or opinions.
    First because you can get most all the coolant out and most Rotax systems only hold 2/3 to 1 gal a flush isn't necessary.
    Many of us use a two year recommended change interval. Can some last longer, yes, but for 2/3 of a gal. and as easy as it is why not do it at the recommended 2 year mark. I'm sure some will come back here and ay they haven't changed their's for years. Some coolant Mfg's will say 3-5 years, but I prefer sooner changes, even in my vehicles.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


    Thank you said by: Al C

  • Re: Radiator flush before replacing coolant?

    by » 11 years ago


    I would agree with Roger that a regular change of coolant is a good idea.

    I used to change mine every year. I would pull the bottom hose off the radiator, and stick a hose pipe in the filler neck.run water through until its clean water coming out and then refill.

    Our aircraft manufacturer recommends using 100% antifreeze which is obviously a ridiculous idea, even though Rotax recommend 50/50. I don't think they understand what antifreeze is and that 100% antifreeze can freeze at around -7 to -12 degrees C if it is not mixed with water and has less of a cooling effect than Evans. It has around half the heat transfer capabilities of water.

    Because of this and because I think it is better, I use Evans coolant which doesn't need changing and for me the temps are fine. It also means I can use a 0.9 bar radiator cap.

    Thank you said by: Al C

  • Re: Radiator flush before replacing coolant?

    by » 11 years ago


    What aircraft do you fly (just curious), and did you notice any increase in operating temperatures when switching to Evans?
    I can't believe the aircraft maker suggested 100% coolant unless they were specifically referring to coolant such as Evans specifically made for use without water. Did you ever figure out what their story is?

    Al

  • Re: Radiator flush before replacing coolant?

    by » 11 years ago


    Hi Al

    Its a trike with a un cowled pusher engine. It is not Evans that they are referring to, it is 100% ethylene glycol.

    When I changed to Evans there was no real change in operating temp, but having said that, I changed from 100% antifreeze, so I wouldn't expect it.

    Mark

  • Re: Radiator flush before replacing coolant?

    by » 11 years ago


    Hi Mark,
    You wrote, in part:
    "...because it's Evans I can use a 0.9 bar radiator cap."

    Well, according to Evans, if I remember right, you can run it with a zero bar cap.
    My personal take it there's a real advantage to that:
    If you get say, a slightly loose hose clamp with no pressure in the cooling system it won't leak at all, let alone work itself off, unlike with a pressure cap on. And if you even had a hose split (yeah I know if we're up on things that SHOULD never happen) you don't have the whole coolant spew out under pressure within minutes... might just seep a little.
    Only way I know to turn the radiator cap to zero pressure is pull out the gasket or drill a tiny hole it in. At your own risk of course, but with Evan's I'd seriously consider doing that to be making the aircraft more fail-safe.
    Your thoughts?

    Al

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