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I'm afraid that when I was instructed to be specific in the title of my post, I kind of said it all... Here is the issue:

I have a 2001 Isuzu Rodeo. It has been going through excessive amounts of oil. No blue smoke, no drips whatsoever.

Through an Isuzu forum I find this is a common problem for model years up to and including mine as oil drain holes for the cylinders that were made in the pistons clog with carbon.

In that the vehicle is a 2001, I can well suspect those little holes are well caked and packed.

Though some folks state that they remove the spark plugs, pour a commercial internal auto engine cleaner called B12 into the cylinders and allow an over-nite soak, other auto-techs state that the only way to clear the drain holes is to tear apart the engine and drill the holes in the pistons out or replace them altogether.

Is there a chemical that will eat away and dissolve the carbon whereas after allowing whatever sufficient soak time is suggested I could then change the oil and have a hope for cleared out ports without damage to the metal engine parts?

Thank-you for your thoughts!

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    $\begingroup$ I don't think that's possible. Carbon is pretty durable. In fact, it is much easier to dissolve the whole engine while keeping the carbon. $\endgroup$ Dec 28, 2017 at 21:44

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If it's pure carbon, then the only way to remove it I can think of is by rigorous oxidation (e.g. by burning in oxygen flow or by reaction with strong oxidants (e.g. conc. $\ce{H2SO4}$, $\ce{HNO3}$)), but this is going to damage the metal parts either, as Ivan said.

However, if the clog is caused by soot and resinous residue from the incompletely burnt fuel, then most likely hot toluene or xylene can dissolve the residue and liberate the carbon particles. Both are widely available solvents which won't damage the metal parts (but avoid contact with rubber tubing) and are also used to remove clogs caused by paraffin wax.

P. S. Both are highly flammable liquids, so do not warm them up using an open fire (e.g. use an improvised water bath)!

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    $\begingroup$ To the OP: Definitely mind any safety warnings and/or get a hold of an MSDS when using either organic solvent. $\endgroup$
    – jonsca
    Dec 29, 2017 at 3:27
  • $\begingroup$ @brucemc777 No prob:) $\endgroup$
    – andselisk
    Jan 4, 2018 at 18:46
  • $\begingroup$ Thank-you, very much! I have to believe that the temperature of the engine at the time would quickly influence the temperature of whichever solvent I was working with. Therefor, instead of pre-heating the solvent, I would think it best to simply get the engine to an acceptable temperature. The problem is, just what now defines "acceptable temperature"... In that I would kind of like to avoid pouring the solvent into a cylinder and having my arm blown off, would either of the afore cited fluids be stable across all normal engine operating ranges? $\endgroup$
    – brucemc777
    Jan 4, 2018 at 18:52
  • $\begingroup$ @brucemc777 Please don't even think of using these solvents with the working engine, or the one that is still hot, this may cause severe injuries. Take off the parts that need cleaning, and apply warm solvent to them (or just soak if you have enough solvent). $\endgroup$
    – andselisk
    Jan 4, 2018 at 18:56
  • $\begingroup$ You might of just saved my life :) $\endgroup$
    – brucemc777
    Jan 4, 2018 at 19:46

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