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Featured Automotive Decarbonizing an Engine with Water: Myth or Fact?

  1. Jan 20, 2015 #1
    I ran across several YouTubes that claim, and apparently demonstrate, that you can clean carbon deposits from a car engine by simply spraying or pouring (very slowly) water into the intake when the engine is fully warmed and running.

    I've never heard this from a reliable source and my reaction is that it is probably an urban legend, like removing rust with coca cola and aluminum foil. However, Eric The Car Guy, in the last video, is usually mainstream, so I'm not sure.

    The principle is alleged to be that, upon hitting the hot piston, the water flashes to steam and dislodges the carbon deposits. And in the second video it asserts the idea for this came from examination of engines whose head gaskets had failed: the pistons onto which coolant had leaked were weirdly clean while the protected pistons were encrusted with carbon.

    What is the real story on this?
    Last edited: Jan 20, 2015
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  3. Jan 20, 2015 #2


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    One would expect anecdotes from the use of water injection in aircraft engines to predate this. Sounds plausible. Probably want to plan on a couple of short running time oil changes after doing this sort of thing.
  4. Jan 20, 2015 #3
    That's something I wondered about. Proponents mention that water injection is a tried and true technique for achieving other goals. Therefore, I read the Wiki article on water injection but it made no mention of engines employing it being especially free of carbon. Do you know if it's maintained they are?
  5. Jan 20, 2015 #4


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    Don't recall seeing such claims re. aircraft use --- doesn't mean it's not been mentioned. Do have vague recollections that pilots were asked to avoid use of water injection unless it was necessary/prudent given circumstances they were in --- does that imply it was rough on engines, or just a "save it until you really need it" recommendation?
  6. Jan 21, 2015 #5

    Ranger Mike

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    No myth was common practice.
    Steam has nothing to do with it. Water injection was used to prevent Detonation at high RPM before all this computer controlled ignition stuff came along. Had side effect of cleaner combustion chambers i guess..i never played with it but know its design purpose.
    We always used ATF ( Automatic Transmission Fluid).
    Was common practice when engines had carburetors. Oil is not compressible (neither is water but will rust things). The idea was to introduce fluid into the combustion chamber and knock off the carbon deposit build up. The oil would burn off and foul the spark plug but it was being replaced anyway so did not matter. This helped a lot with the cars owned by the little old ladies who never got the engine to full operating temperature going to the local grocery. Those engines were a mess to rebuild. The intake manifold heat risers were always clogged up with carbon. Anyone who has done this knows carbon requires a hammer and chisel to remove. When you use ATF at high idle speed you are essentially beating he-- out of the carbon deposits and everything else in the combustion chamber.

    btw - you get blown head gasket when you have very hi compression ratios ( not likely today) or have cast iron engine block and aluminum cylinder head. Eventually the result of differing thermal expansion rates will cause a leak to the water jacket passages. This usually happens around 85,000 miles of a cheap iron / al engines life span. Then you have to pull the head and replace the gasket. And to do it right, mill the head surface flat as it is probably warped. ( this is the typical scenario these days with little cast iron 4 cylinder blocks and aluminum heads)

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    Last edited: Jan 21, 2015
  7. Jan 22, 2015 #6
    Sprint cars run on alcohol that has a small amount of disolved water. The engines are spotless, you can't even read the plugs.
  8. Jan 22, 2015 #7

    Ranger Mike

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    I will give you that. :cool: Methanol is hygroscopic which means it will absorb water vapor directly from the atmosphere. So you are going to have absorbed water diluting the fuel value of the methanol .But it helps suppresses engine knock. You have to watch your fuel cans real close. Containers of methanol fuels must be kept tightly sealed. It burns " cleaner" than racing gas and with the added water so you would expect clean piston domes etc...
    I hate the stuff mainly because you can not see it burn..one time as a kid i was at the pit gate when a sprint car raced into the pits at 35 mph and slammed on the brakes. The driver leaped out of the car. A crew man "hosed" him down with a fire extinguisher...he was on fire..i never would have known..
  9. Jan 22, 2015 #8
    The ethanol that is put in our fuel is problematic, for one it's of poor quality and secondly it attracts moisture. Not good for metal gas tanks or fuel lines . You have a difficult time starting any machinery that isn't used all the time.
  10. Mar 28, 2015 #9
    I have read about this as being a beneficial side effect of using water injection on an engine. AEM makes a water only injection kit and I think they mention that it can keep cylinders and valves clean. It makes sense, don't some shops remove the head and intake and clean them with steam? I wouldn't use tap water though I would use distilled water only, tap water could leave deposits of its own.
  11. Mar 28, 2015 #10

    Doug Huffman

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    My VW TDI users forum had many stories of hydrolocking diesel compression ignition engines with Sea Foam brand.
  12. Apr 25, 2015 #11


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    In the UK there was a craze for steam injection in about 1970. The vehicle had a gallon container of water in the engine compartment, and a copper tube went from this and passed across the exhaust pipe. The resulting steam was led into the air filter box. It was supposed to raise the octane rating of the fuel and I understand that it did work.
  13. Apr 26, 2015 #12
    I had a '65 corvair turbo in 1985 , you couldn't get leaded fuel , so I opted for a holley wat er injection unit . With very few sensors , it injected (sprayed) water at higher vacuum and solved my detonation problem beautifully.
  14. Apr 30, 2015 #13
    After mowing my whole lawn and mulching a bunch of leaves my mower was nice and hot. It's a Kawasaki 10 Hp engine, i pulled off the air intake cover and pushed the throttle up to about 2/3 power, i then slowly dropped distilled water in, it sucked in the water, the rpm would drop a little and make a popping noise, i did this about 15 times using only a small amount of water each time. The engine definately idles better and ill see how it performs next time i take it out. I think this is a great trick that costs practically nothing and is very easy to do, i would recommend it. Im trying to find a way to do it to my VW 2.0L Turbo, just gotta get a hole in the intake manifold tube.
  15. May 1, 2015 #14
    I wonder if the carbon might cause problems down stream by getting lodged in cat converter .
  16. May 2, 2015 #15
    Thats a good question, maybe it would be wise to disconnect it before you did this trick. On my mower engine i don't think theres any cat to worry about, only a small exhaust.
  17. May 4, 2015 #16
    Valves get carbon build up that hinders air flow, reducing performance . Regular decarbonizing might be a smart thing to do.
  18. Nov 4, 2015 #17
    Here is a very mildly educated guess at what might happen re water cleaning carbon in an engine.

    Steam reacts with carbon to form synthesis gas, this is part of the process to produce feedstock for a Fischer–Tropsch plant. It might be that the fine mist of water turns to steam on contact with the hot internal parts of the engine and that steam then reacts with the available carbon.

    Pouring water, out of a cup, jug or hose into an engine is probably not the best way to try test this process.
  19. Nov 4, 2015 #18


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    Just by way of trivia, the 1962 Oldsmobile F85 was delivered with the Fluid-Injection Jetfire engine that was turbocharged. Oldsmobile referred to the water/alcohol mixture as 'Turbo-Rocket Fluid' that was used as a detonation suppressor. I don't know if the engines were any cleaner though.
  20. Nov 5, 2015 #19


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    I have seen how clean a combustion chamber is when a head gasket fails between a coolant channel and cylinder. I have no doubt that water can clean carbon deposits.

    I don't know if 5 minutes with a plant sprayer does the same job or not though.

  21. Nov 10, 2015 #20
    Carbon build up might raise compression and even a small build up at the valve base hinders air flow . Seems like these two might cancel each other . I'm getting fascinated by fuel vaporization , let me know if you have any insight .
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