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  1. 12-71 coolant change details

    I am planning to do the coolant change on our 81 12V-71 TA Detroit's soon.

    Here is where I am at so far:
    • I have found a local source for the Detroit coolant.
    • I have also found 5gal containers and lids. The store is uline.com if you are looking for cheap pails!
    • I found a local disposal place that can take up to 50 gallons per day.
    • I also know each engine will be around ~25 gallons of coolant each.
    One thing I am unclear on is the exact drain locations for the coolant. Our local mechanic has mentioned there are a handful and I wanted to reach out and see if anyone has a good handle on that so I can know right off the bat how to do it.

    Thanks for the help as usual!

  2. #2

    Re: 12-71 coolant change details

    Front of engine above main pulley. HE or HE piping. Oil cooler. Water jackets (2). Rear block (2); one is over and above the starter so protect it. I counted 7.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  3. Re: 12-71 coolant change details

    Quote Originally Posted by racclarkson@gmail.com View Post
    Front of engine above main pulley. HE or HE piping. Oil cooler. Water jackets (2). Rear block (2); one is over and above the starter so protect it. I counted 7.
    Thanks Robert. Did you just drop each drain into to the pan and scavenge it from there? I was thinking about trying that after using a transfer pump to empty the heat exchanger reservoir as best as possible.

  4. #4

    Re: 12-71 coolant change details

    The drains have petcocks on them so you don't need to drop them into the bilge. My recommendation
    would be to drain the old coolant and replace all the petcocks with new units that incorporate a small
    hose barb that you can attach a length of hose for future easy clean coolant changes. It seems that
    no matter how careful you are there will still be some spilled coolant with the original petcocks.

    Walt

  5. #5

    Re: 12-71 coolant change details

    While its out pipe a drain in it like Robert did. I wish I had seen his pictures before I recently changed mine. I will do this next time. I would get a couple of spare petcocks too in case one of them is frozen and needs replacing.

  6. #6

    Re: 12-71 coolant change details

    Quote Originally Posted by MVCaprice View Post
    Thanks Robert. Did you just drop each drain into to the pan and scavenge it from there? I was thinking about trying that after using a transfer pump to empty the heat exchanger reservoir as best as possible.
    Do oil cooler first, then HE. You’ll get majority from there.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  7. Re: 12-71 coolant change details

    Is it worth pulling the heat exchangers and getting them cleaned at that time as well? Seems like it would be easy enough to do. Anything else that would make sense while the coolant is out?

  8. #8

    Re: 12-71 coolant change details

    Where are you located? I'm down in Florida and i used Napacool, available at napa and distilled water. Of course we don't really face many freezing conditions so it may not work for you?

    EDIT: I have 8v-92's, may not be the same recommendations for 71's

  9. #9

    Re: 12-71 coolant change details

    Quote Originally Posted by MVCaprice View Post
    Is it worth pulling the heat exchangers and getting them cleaned at that time as well? Seems like it would be easy enough to do. Anything else that would make sense while the coolant is out?
    It's be a good time. If not, you can clean the entire raw water system in place at a later date.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  10. #10

    Re: 12-71 coolant change details

    Only flush and fill with distilled water, PH too high in tap water. Get lots of cases of distilled water.

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