Engine coolant smells like a solvent

Hi Roy and thank you for the advice. Since the most of the six spark plugs on this vehicle are very hard to get to, would a good place to start be the (chemical block test) for hydrocarbons in the coolant? Today I tried to check for coolant in the oil by bleeding some oil and/or coolant from the oil pan, but just could not get the oil drain plug loose. Maybe vise-grips and a mallet are needed? Since some antifreeze types fluoresce quite well under UV light, I tried using a ultra violet flashlight (like for checking for leaks in an AC system with a dye) on the dip stick, inside valve cover and in the radiator, but it did not reveal much, not even on the coolant in the radiator. Maybe other types of antifreeze would fluoresce better.

Hi Roy, no, I have not yet tried the UV kit, I did not know about them. I did manage to get the oil drain plug out and allowed approximately (one) ounce of cold fluid to drain into a clear plastic bottle, see image. Then drained out (one quart). But did not see any more antifreeze, but the oil color is a dark brown/black color using a white light LED flashlight, viscosity seemed more like warm oil, not like a milkshake. Question, how can the hydraulic lifters can be flushed after the repairs are done? Also, what is your opinion about those head gasket sealant products like bars leaks ans steel seal for a temporary fix? I tried Bars leaks on my 1991 explorer's V6 a few years ago, it seemed to work for a while as long as it was not a cold night, but then the coolant leak came back. I am thinking of retiring both the 1991 and 1998 Explorer's to California's salvage yard in the sky, but with the 1998, I cannot do that this month. Horse and buggy days were easy, but not allowed now, too much methane.

Hi Roy:

To flush or not to flush. With antifreeze/water in oil and combustion gasses in coolant
after the leaks are repaired, would you recommend an engine flush? I have read many articles from on line mechanics that disagree with this issue. Some say, "no way, it will damage the engine" and others say "you have to in order to prevent the same acidic compounds from continuing to damage engine".
Same question for the cooling system, can you recommend any product that addresses removal of combustion gasses and or oil in coolant and the acidic conditions it creates?
Thanks for your help.

Question, the additive to remove dirt and debris from the cooling system that most shops have, does it also (cleanse) the system of gasoline and combustion gasses? So that future chemical block test of the radiator will not give false readings for a previous problem.
Thank you much.