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  1. #1
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    Aug 2013
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    Default Fresh water cooling system flush

    [This is really for my Triumph Herald, which returned to the road on Saturday after a twenty year restoration (hooray), but it would apply to boats as well so ...]

    What would people recommend for flushing out a fresh water cooling system? In Ye Olde Days I used to use a two-part powder product from Holts. The first part cleaning things out and the second was supposed to give longer-term protection. That seems to be gone now. Holts still make Speedflush, but I never had much luck with it before.
    "Seamen are always wanting to do things the proper way; and I like to do them my way."

  2. #2
    Join Date
    Nov 2009
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    Default Re: Fresh water cooling system flush

    Rydlyme is the go to product .... but if it all looks clear then I'd just flush with water.

    Richard

  3. #3
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    Default Re: Fresh water cooling system flush

    Quote Originally Posted by RichardS View Post
    Rydlyme is the go to product .... but if it all looks clear then I'd just flush with water.
    Thanks, Richard. The coolant stayed reasonably clean in testing, but now that I am actually running the car it has gone a nasty rust-brown shade, presumably as corrosion from inside the engine gets knocked loose. I can give the block a reverse flush, but something to clean the surfaces as well would be nice. I see that Rydlyme is 5% hydrochloric acid - is it better, do you think, than just getting hold of some acid?
    "Seamen are always wanting to do things the proper way; and I like to do them my way."

  4. #4
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    Nov 2009
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    Default Re: Fresh water cooling system flush

    Quote Originally Posted by JumbleDuck View Post
    Thanks, Richard. The coolant stayed reasonably clean in testing, but now that I am actually running the car it has gone a nasty rust-brown shade, presumably as corrosion from inside the engine gets knocked loose. I can give the block a reverse flush, but something to clean the surfaces as well would be nice. I see that Rydlyme is 5% hydrochloric acid - is it better, do you think, than just getting hold of some acid?
    I can't see any reason why you shouldn't use dilute HCL if you have it but make sure you flush through several times with water after use as I'm not sure that residual acid would be a good idea.

    Richard

  5. #5
    Join Date
    May 2007
    Posts
    38,184

    Default Re: Fresh water cooling system flush

    Quote Originally Posted by JumbleDuck View Post
    Thanks, Richard. The coolant stayed reasonably clean in testing, but now that I am actually running the car it has gone a nasty rust-brown shade, presumably as corrosion from inside the engine gets knocked loose. I can give the block a reverse flush, but something to clean the surfaces as well would be nice. I see that Rydlyme is 5% hydrochloric acid - is it better, do you think, than just getting hold of some acid?
    Is there antifreeze in there?
    Either just change the coolant until it stays clean, or use a central heating cleaner?
    In the past I've used a phosphoric based rust remover just in the block and head.
    Got a fair amount of crud out and the engine ran clean thereafter.
    Last edited by lw395; 27-08-19 at 14:04.

  6. #6
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    Aug 2013
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    SW Scotland
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    19,649

    Default Re: Fresh water cooling system flush

    Quote Originally Posted by RichardS View Post
    I can't see any reason why you shouldn't use dilute HCL if you have it but make sure you flush through several times with water after use as I'm not sure that residual acid would be a good idea.
    Thanks. I'll investigate. Whatever I use will be very well flushed out!

    Quote Originally Posted by lw395 View Post
    Is there antifreeze in there?
    There was, but the engine sat dry for fifteen years and I think it's probably rust from then which has finally started coming out.

    Either just change the coolant until it stays clean, or use a central heating cleaner?
    In the past I've used a phosphoric based rust remover just in the block and head.
    Got a fair amount of crud out and the engine ran clean thereafter.
    Central heating cleaner is an excellent idea, not least because I can get it locally. Thanks.
    "Seamen are always wanting to do things the proper way; and I like to do them my way."

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