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  1. #1

    Muriatic acid for cleaning the cooling system on a fresh water engine?

    I have 426 Chryslers (fresh water system - no heat exchangers) and was wondering if I should use some muriatic acid to clean the system or not..

    I do not think the engines ever had the cooling system de-rusted, so I am thinking this would take and crud out of the engine and the risers...

    I can dilute the acid (1 part acid to 2 parts water) to make it a 33% solution, and feed it through the water pump, wait a minute and flush the system throughly.

    Not as thorough as taking all the pieces apart and soaking them in buckets of acid, but it is much more practical and safer...

    Would that work or is there a better way to do this?
    Akin Tosyali
    Hatteras 41 -Barbaros


    Barbaros, Hatteras 41' Before and after restoration

  2. #2

    Re: Muriatic acid for cleaning the cooling system on a fresh water engine?

    If you are not having issues with the cooling system, I would not recomend an acid boil in a raw water system.

    If you are having cooling issues, check the t-stat first. If Ok then do the 33% mix, let sit for 1 minute and flush.

  3. #3

    Re: Muriatic acid for cleaning the cooling system on a fresh water engine?

    for cleaning the cooling system on my car i usually use oxalic acid. it has never hurt the radiator, hoses or engine parts (both iron and aluminum). i get it at the hardware store by buying wood bleach. if you remember the good ol days of car repair there was a product that had a paper tube with the radiator cleaner in one end and the neutralizer in the other end. the cleaner was oxalic acid. the neutralizer was baking soda.
    if you can't find oxalic read the genesis post about cleaning the cooling sytem with phosphoric. i have also used that on car cooling systems with no ill effect.
    muratic is very serious stuff. the fumes coming out of the cooling sytem can definitely kill you. have lots of fans going to keep fresh air flowing. and wear a respirator. if you are going to use muratic below decks you might want to have paramedics standing by to resuscitate you.

  4. #4

    Re: Muriatic acid for cleaning the cooling system on a fresh water engine?

    I second Passages' statement about problems/no problems. Check the RW pump impeller too if you are overheating.

    I would stay away from muriatic acid. I recently flushed my heat exchanger with Olympic Deck Brightener (oxalic acid) from Lowe's. It did a great job. phosphoric acid (metal prep in Lowe's) will also work.

    I don't think any acid bath will get much rust out of the risers by a quick rinse. For that, I would remove them and tap the sides with a hammer to break the rust free. If they are over 6 years old, I would replace them.
    Lost in a fire - 1986 43 MY, CAT 3208T

  5. #5

    Re: Muriatic acid for cleaning the cooling system on a fresh water engine?

    Hi, Before I retired (last month - yippee) I was actively working in the field of acid cleaning. There are a few points regarding using muriatic (hydrochloric) acid for descaling your engine cooling water systems that you should consider.

    First is that HCl is fairly slow in dissolving rust, particularly when the solution is cold. Typically, you would want to use a warm solution, about 160 F, and circulate the acid for several hours. The circulation is very important and cleaning may be very poor without it.

    Second point is that unless the acid is inhibited, it will attack the metal as well as the rust. You can probably find inhibited acid cleaners to buy - sorry but I don't know what is available in the US, but there are similar products in the UK.

    Third point is that if the system has heavy rust scale present, say anything over about 1 mm thick, then the acid will detach the scale but not actually dissolve it. So you will end up with a lot of loose crud in your system that will need to be flushed out. If the system is difficult to flush it is likely to cause bad problems by blocking up small diameter water passages.

    Fourth Point - If there is a lot of rust scale present and this dissolves during the cleaning, then the inhibitor will stop working and you are liable to cause damage by the acid attacking the metal. When we used HCl we used to continually analyse the solution for dissolved iron and dump it when the iron content reached 0.5%.

    Sorry if this sounds a bit negative but these are real possibilities and you need to think about potential gains versus losses before starting.

    If you are sure that the system will benefit from an acid clean I would recommend using inhibited sulphamic acid. This used to be readily available as a Castrol marine product called DP Descaling Powder - not sure if it is still though. Oxalic acid is also OK and fairly safe to use. Personally I would not choose phosphoric acid without knowing if the scale contains substantial amunts of calcium hard water scaling. If it does, phosphoric acid will not be very effective as it reacts with the water scale to form calcium phosphate which is very insoluble and that blocks the acid from dissolving more scale.

    Hope this helps!
    OldLimey? Something to do with the Royal Navy, limes and scurvy? Nope! Just geriatric and sour!

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