In using this technique, how necessary is it to disassemble the engine before immersion? In other words, can a lazy man just throw the whole thing in (sans plastic parts) without damage to the guts? If so, it seems to me that flushing out the anti-freeze with methanol or some such would be a good idea. What say ye?

Dave Mo

    As Bob has pointed out, it can depend on what your idea of clean is, and the engine. I have successfully done the quick dunk and run on a couple of plain bearing engines such as Foxes, McCoys, and OS FP engines with no problems, Just drain them as best you can (pop off the back plate if need be), then flush with some old fuel, put in a known good, used plug, and burp them several times to  blow it everything. I short two or three minute bench run will clear them out also. I have done one of my ST.51's that way, but it was in regular use, wasn't stuck, just wanted to get the head and crank case clean. I flushed it out, burped it several times, installed in the airplane and went flying. Would I do it to a high end PA, Ro-Jett or expensive Russian engine? Probably not.
  Type at you later,
   Dan McEntee

DaveMo,

A few things to consider:

--If your engine is a blue OS, the antifreeze will take the blue paint off

--Pure antifreeze will not rust up your engine. Old used up antifreeze may, since the anti-corrosion additives may be used up. High temperatures and long exposure times increase the formation of corrosion. If you have added water to your antifreeze, then you have also increased the risk of corrosion. If you wash it down afterwards with water, you must drive the water out before storing it, else you will get a rusty crank, rusty bolts, etc. Personally, I don't like to wash an assembled engine with water.

--If you heat the engine up after rinsing it without oiling it first, you will get a bit of flash rust on the steel parts. This is simply a very thin oxide layer. But you don't want oxides inside your engine because they are abrasive. If you flush with oil or fuel, and therefore dilute any remaining trapped water you have just improved things. If you flush with fuel and then run it long enough to evaporate any remaining moisture, you should be golden. You could do the same thing in a low temp oven as long as you rotate the crank so that all the water can gas off. Taking out the plug and the backplate off ensures no trapped water.

--You need to be more concerned if an engine has ball bearings. These are generally UNS52100 steel and have no inherent corrosion resistance.

--This is actually one of the reasons WD-40 was designed--for water displacement. No lasting lubrication or corrosion prevention that I can see, so it still needs to be oiled afterwards if you use it.

The Divot

Divot and Peter:

Very generous of you both the chip in here. I've got the silver, non-ball bearing engine. Will open the case and remove the head. The no freeze juice I've got on hand is unused, but with a low percentage of water in it. The regimen, thanks to you gents, will be as follows: twelve hours low temperature soak followed by a boiling water (drop of soap added) dip; WD-40 blast; finally after-run oil. Will take it out next week for flying. I'm encouraged to hear from Peter that the treatment might give me a few more RPMs.

Thanks again!

DaveMo...