Cleaning out coolant passages in heads?

Discussion in 'Workshop Forum' started by Dr.Jeff, Dec 20, 2018.

  1. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I have a head that's off the engine and stripped down to do a little mild port clean up, resurfacing, etc. And the coolant passages (little internal compartments within the head) have a lot of scale, rust, corrosion build up in them. In the past this always seemed to clean out well when heads returned from the machine shop, after being worked on and cleaned up. But when I asked the machine shop about it, I was told the EPA has banned them from using agents to the point their cleaners cannot remove any of the scale, etc. Basically I was told there is nothing that can be done and to just ignore it. That sounded odd to me so I went to two other shops, but was given the same answer.

    There must be a method of cleaning out the coolant passages? Perhaps something the shops cannot use, but we can? With the head stripped down it can be soaked, but in what? Perhaps the rust remover products like "Evap-O-Rust", or a acid solution, or "CLR" (calcium, lime, rust remover), or ??? In past experiences most of those things don't seem to do a lot with other stuff but I'm open to ideas. One factor is being able to clean out the coolant passage areas but not harm the combustion chambers, valve guides, seats, mating surfaces, etc. There are too many little odd-shaped openings everywhere to try and contain a solution only within the coolant passages, rather than submerge the entire head. What has anyone tried, and how well did it work?
     
  2. )Hi Jeff,

    good question, but unfortunately I don't have an answer (but I do have the same question :)).

    I'm not sure that it is just rust and scale we need to worry about either. Once, whilst replacing the heater tap, I noticed that it was full of some kind of "goo". I then realised that it was the remnants of a "radiator stop leak" that I had used back when I was young and stupid (now I'm older but still stupid). Anyway, it made me think what this stuff was still lurking around in the coolant passages in the engine.

    So certainly interested in the response...

    Cheers,
    Dom.
     
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  3. Dan Sarandrea (Phila)

    Dan Sarandrea (Phila) Waitin' On Parts...

    Location:
    Philadelphia, PA
    I have a good friend who has operated his own automotive machine shop for close to 35 years. Indeed, the caustic sodas that used to be widely used in hot tanks and were strong enough to take off 4 or 5 layers of skin in seconds if you weren't careful, are no longer used. They were extremely effective in removing everything but the cast iron! He has told me that type of solution was never used for aluminum components anyway as it would eat them up, but "back in the day" there were not a lot of aluminum components in typical American car engines so it was not much of a concern.

    Today's solutions are just detergents which pretty much bind with and take oil/grease/dirt away but are ineffective on paint and rust/oxidation.

    If you are looking to clean out head passages you could block off side openings in the head and pour in a solution of whatever would attack the scale but be kind to the aluminum. It would be simple to make some sort of block off plate for the stat housing mating surface (maybe out of a scrap of metal, wood, or plastic, then plug up the heater outlet port and the various sending unit ports, and the two small intake manifold coolant holes. Then position the head so that the block mating surface is level and up, and pour in your solution and let it sit. If you had some sort of industrial heating source, you could position the head to receive heat from underneath, thereby heating the head and the solution, as a hot or close to boiling solution would be expected to work better.
     
  4. ecohen2

    ecohen2 True Classic

    Location:
    Arlington Va
    Ooh I am super interested in this... Does anyone have a solution for doing this without taking the engine apart? After my car sat for almost 30 years I have found grey/white gunk throughout the cooling system...
     
  5. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Hi Dan. This is really the biggest part of the question; what solution could do that? If it is safe for aluminum then the entire head could just be submerged into it. That would preclude the need to plug all the holes.

    One substance I've used to clean the general cooling system is Oxalic Acid. At one time this was the ingredient in one of the best radiator cleaners on the market. It does a good job removing a lot of the usual crud in a normal cooling system (but it requires a very thorough flushing and neutralizing). However it seems a head gets much worse build up than a rad. I guess the higher heat levels has a lot to do with that. So I'm not sure if Oxalic Acid will do the trick. I have a fairly large electric cooker that the solution could be kept hot in. I'll have to see if the head will fit in it and give it a try.

    Other stronger acids or bases (e.g. Muriatic Acid, Lye, etc) would work if you could be sure it would not get on anything other than the internal coolant passages. But I don't trust it enough to try; too big of risk ruining the head.

    Another "trick" I've heard of to clean the coked oil suit out of diesel exhaust manifolds, is oven cleaner. But I tried that on a gas engine manifold and it did nothing. Not sure if diesel coke is different or if the 'trick' is bogus. I imagine it won't do anything for the coolant scale.

    I don't think the head scale is really a rust issue. It can get rusty looking, but it seems to be more of a mineral deposit. So I don't think rust removers will cut it. And it is way too heavy for mild treatments like vinegar, "CLR", etc. I'm definitely open to suggestions.



    Ed, the Oxalic Acid solution might work for your needs. See if you can find some details online. I might still have a reference for it, I'll look.
     
  6. Dan Sarandrea (Phila)

    Dan Sarandrea (Phila) Waitin' On Parts...

    Location:
    Philadelphia, PA
    Look for stuff called boiler cleaner/descaler. A lot of these products are either acid-based or some new biodegradable stuff.
    https://www.google.com/search?q=boi...fAhVwQt8KHbavDl0QsAR6BAgDEAE&biw=1920&bih=967
     
  7. Tedd

    Tedd Daily Driver

    Caustic soda: drain cleaner or sodium hydroxide

    I do not endorse or know if that is what they use, but thought I would mention the chemistry and general availability. I think it will attack the aluminum since aluminum is soluble in acids and bases, amphoteric.

    You might try use hot solutions to increase dissolution with vinegar or CLR, but limit exposure time. Hot pine sol works good for carb cleaning, just not great to smell.
     
  8. Simon Oaten

    Simon Oaten Daily Driver

    Oxy acid works fine - as Jeff said "it used to be in almost all rad flush compounds" ......

    oven cleaner does work on baked on carbon .....it will "eat" ally if left on for any real length of time ........

    sod hydro - will eat ally ....
     
  9. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Ha, never even knew such a thing existed. Living in temperate climates all my live I'm naive to such things. I did a quick search on this. According to Wikipedia, "Notable descaling agents include acetic acid, citric acid, glycolic acid, formic acid, phosphoric acid, sulfamic acid and hydrochloric acid." I'll have to search more to find something safe for aluminum. Could be very promising though, I'm sure there must be one that is buffered enough to be safe yet not so much to prevent it from working.

    That brought up another idea; coffee pot cleaners. I'll have to see what is actually in them, but they do an amazing job of cleaning the scale out of appliances. Most likely it is one of the above listed chemicals.
    Oxalic acid is still on my list. As noted it has been used in cooling systems without damaging aluminum. However it isn't extremely good at really heavy scale.


    That is 'lye'. Back in the days when machine shops used 'hot tanks' for parts cleaning they would use it. But as Dan said earlier, only for cast iron parts because it will eat up aluminum unfortunately. Although I've been known to try some rather risky things, frankly I'm too afraid of ruining a head with something this strong. Appreciate the idea though.


    Another thought came to mind on this subject. Even with the head stripped down, the valve guides are still in it. I believe they are made of bronze? Although bronze is harder than aluminum, I wonder if submerging the entire head in something that is safe for aluminum might still damage the valve guides? The current guides are good so I was hoping to avoid any unnecessary work/expenses on this. I don't think it will be an issue?
     
  10. MikeHynes

    MikeHynes True Classic

    Location:
    Goodfield, IL.
    I did a bit of research, back in the day, to find the best aluminum cleaning solution for a high volume commercial mechanical repair shop. The best solution we came up with was a parts cleaning cabinet that used high pressure hot water with a strong detergent. It was MUCH easier to do a good job of cleaning cast iron parts. The aluminum cabinet left gaskets in place and didn't clean inside parts very well. There are probably better solutions out there today as it's expensive to hand clean aluminum parts.
     
  11. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I would have thought the same thing. But at least locally there isn't. Makes me wonder what people are getting back after their heads are worked on.

    I've been doing some reading on "descalers" for boilers. The consensus seems to be they use rather strong acids (HCL mostly). But boiler units are not made with any aluminum or other soft metals, so it's good. I found one product that gives the impression it is for descaling, and safe for aluminum. But upon closer reading it is actually a scale preventative, not remover. Something of a passivation process, mush like automotive antifreezes have.

    In the research I also learned more about scale in general. Due to its typical chemical composition, the process to remove it must be a acidic solution. I guess the goal would be to find a weak enough acid to preserve the aluminum, but strong enough to eat the scale. Or at least eat the scale before it eats too much of the aluminum, because there really isn't anything that is selective enough to do one without the other. And as was mentioned earlier, heat will improve its action the same as with any chemical reaction (adding energy speeds things up).

    I'm still curious to find out what type of acid 'coffee pot cleaners' are made of. Otherwise oxalic acid might be best. Regular vinegar is milder and therefore would be less effective, but very cheap and safe. So it might be worth an experiment to see if it does any good first. The water where I live is very hard, so calcium deposits build up quickly on faucets, etc. I've tried the typical products like "CLR" and vinegar with no benefit. So I'm not optimistic about it.
     
  12. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Interesting. I just looked up coffee pot cleaners. Appears they are "sodium carbonate", which is a strong base. According to what I read about typical water scale, it won't do anything to remove it. But it might help to prevent it in conditions with hard water (neutralizes the pH). It also seems to eat aluminum (I thought some coffee makers had aluminum parts?). So I doubt it will be very effective on aluminum heads.
     
  13. I think oxalic acid is the active ingredient in Oxy-Clean which I used to clean out my gas tank successfully. I have not tried on rust yet but it sure did a number on the inside of the gas tank.
     
  14. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
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  15. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Here are a few things I found online (so it must be factual, right?). Sorry for the long post:

    "According to the U.S. Motors's Table of Corrosive Chemicals, hydrochloric and sulfuric acids are known to damage aluminum parts in motors, drives and gears. You can reduce hydrochloric acid's effects through dilution. Very weak solutions of sulfuric acid will not damage aluminum parts if you keep them at room temperature. Boric, carbonic, lactic and nitric acids usually do not cause significant damage to aluminum. Chromic acids cause moderate damage, depending on both the concentration of the acidic solution and the temperature."

    Another source from the aircraft industry stated, "Weak acids such as citric acid, formic acid and sulphamic acid are suitable for use with metals such as aluminium, zinc, copper and nickel. Although these metals will be affected by these acids, this will be much less severe (than with) strong acids such as hydrochloric acid, nitric acid, sulphuric acid and phosphoric acid."

    The strength of a acid is a good indicator of how corrosive it will be on the head. A lower pH number means a stronger acid. A acidic pH of around 2.5 should be the lowest (strongest) to use for aluminum. Although that might sound like a strong acid, especially when hydrochloric acid has a pH of 2, but it really isn't. The pH scale is logarithmic, so a pH of 2 is ten times stronger than a pH of 3. Examples of acids around 2.5 pH include the ones mentioned in the aircraft reference; citric, formic, and sulphamic. Those were listed as causing low damage to aluminum. By comparison, the pH for the weak acids listed in the other reference (boric, carbonic, lactic, nitric) as causing "no damage" to aluminum, are between 3 and 5. It might be easy to say, let's play it safe and use one with a pH of 5. However recall that 'scale' is harder than aluminum, so it will take a stronger acid to eliminate it. Kind of a trade off; the stronger the acid the better it gets rid of the scale, but the more it eats the head also. And keep in mind, all of these are for pure forms of the acids. Dilution lowers the pH, so the more water you add the higher the pH number, and the weaker the acid. Therefore you could adjust the pH by the amount of (pure or distilled) water you mix the acid with (always add the acid to the water, and not the other way around). Temperature and length of time of exposure also have an effect, as discussed earlier. And consider the availability and cost of these acid choices. Some can be difficult to buy locally in the quantities needed, and very expensive.

    What are some options for our application:
    We would have to do some shopping to see what is readily available and affordable.
    Oddly distilled vinegar is listed as having a pH in the upper 2's, so it might actually work...especially if not diluted and kept heated and left soaking long enough. But check the label, the stuff you buy at the grocery store might be diluted and a weaker pH? A temp of around 150 degrees F will help.

    A solution of 16 oz oxalic acid per 2 gals water was discussed for cooling system flushes. I don't know what pH that would yield...a simple litmus paper test strip will find out. It could be mixed in a stronger concentration if needed. In my area it is not commonly found. But in areas with wet climates it is often sold as "wood bleach", used to clean the discoloration off wood decks. I bought some in powder form online for a moderate price, but hopefully it is less expensive if found locally.

    Phosphoric acid works great for rust. That does not necessarily mean it is good for 'scale' though. Although it is stronger than the others, it is considered a mild acid so it might be a good option for a head (depending on dilution). If I recall, the stuff you can get easily at local hardware stores is around 20% solution, which should be about the right strength (need to test the pH). I have a few gals of it left over from cleaning a couple X1/9 fuel tanks. It was highly diluted in order to fill the tanks, so it will be very weak (it was really too weak for the fuel tank cleaning). Unfortunately it also got badly contaminated with that ugly tar crud we discussed with those tanks. But I might try filtering it and check its pH. I know it makes a great aluminum cleaner/polisher when wiped over the surface, so it will be interesting to see what happens when scaled aluminum is soaked in it.

    According to the MSDS sheet, "CLR" is a mix of water with lactic acid with a little gluconic acid and lauramine oxide. The first two are very mild acids used in lots of industries, including medicine, food, cosmetics (makes a great facial peel). Apparently their role in CLR is similar to that of the acids discussed earlier, to break down the minerals in scale. The last one is a very common surfactant, so it's role is likely to clean things up as the acid goes to work. I think it would be too mild to be really effective for our use. The concentrated version (CLR Pro) isn't exactly cheap (I think close to $30 a gal), and it should definitely be used at full strength. So I'm not keen to even try it, I think there are better options.

    I might still have some muriatic acid left over from other uses. It could be diluted a lot to get the pH up to the 2.5 range. However it gets into an area of extreme caution for use on aluminum, so I'm not certain it is appropriate.

    After my holiday guests have left and I can get things back to normal, I'll experiment with some of this. Especially the ones I have easy access to (oxalic acid, vinegar, and phosphoric acid).
     
  16. carl

    carl True Classic

    Location:
    Virginia
    I have not looked at my spare head (X head, not the one on my neck) but I wonder how much corrosion could be removed by mechanical means such as bottle or gun barrel brushes.
     
  17. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Unfortunately there is very little access to do that. Picture the coolant passages as shallow flat chambers, with the openings at 90 degrees from that plane. Therefore those small openings only go a very short distance before hitting a wall, with the passages heading off to the sides in various directions. And the chambers are not wide open areas either, but something of a labyrinth of multidirectional tunnels. Many of them are quite far from any of the openings. Frankly, even trying to fill the passages with a cleaning solution would be difficult; there will be air pockets, different planes, lots of little openings, etc. Remember it is a pressure fed system in operation, so a flow of coolant is forced through this labyrinth. I think the best way to fill it with a cleaning solution would be to submerge the entire head in a deep enough bath that it can be rotated about, allowing all of the passages to fill. And that makes the selection of cleaning solution more critical, to avoid damaging the machined sealing surfaces, valve guides, etc. Although an advantage will be the ports and chambers will get decarboned in the process.
     
  18. Tedd

    Tedd Daily Driver

    Some data attached, seems to me that acetic acid/vinegar would be a good choice. I think you could increase the action through temperature. Any organic acid probably would likely act similarly: citric, oxalic. A material like aluminum has lots of data such as attached. Dissolving only the oxide alone is tough, as aluminum is an active metal, very unstable without the oxide layer.

    If you want to lightly etch, you probably could dilute more active agents like hydrochloric acid or sodium hydroxide. If you have the time test option.

    The is an equivalent to navel jelly for aluminum. That might be worth trying.
     

    Attached Files:

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  19. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Great stuff, thanks Tedd.

    I'll have to look it up, but I seem to recall it is actually a phosphoric acid solution? Or maybe that's what the one for iron is made of. That would make more sense. But a gelatinous substance might be more controllable to work into just the coolant passages and not the entire head.
     
  20. Tedd

    Tedd Daily Driver

    I think aluminum jelly has phosphic acid. There might be other ingredients to inhibit corrosion. The nice thing for your application is the ability to coat the surface due to being a jelly. I have some but can’t remember using it.
     
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