Engine flush... Yes or No???

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mbaird said:
Honda engineering sent out a memo to all service departments stating that under NO circumstances should you flush engines . It said they have had catastrophic engine failures due to flushes .
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And it's entirely possible. Once an engine gets heavy sludge in it, it's time to physically clean it out......or tear it down for a rebuild.
 
I would not flush it with any type of 'flushing' agent [ oil ]. You might find things like it starts burning oil when it didn't before. That is because the flushing agent has dissolved the seal around areas such as the piston rings that have built up over the years.
Just replace the oil with good quality non-detergent oil.
 
RustyRatRod said:
When I was suspicious my 170 had sludge in the bottom of the pan, I pulled it, put it on the stand, got the pan off and sure enough it had about 1/2" or more sludge in the bottom of the pan. It was blocking the oil pickup causing the oil light to stay on extended periods on cold startup. I cleaned it all out, replaced the rod and main bearings even though they were good, put a new oil pump in it and a new timing chain set in it and back in it went. I just now pulled it back out to swap in the hot 225 I put in a couple of weeks ago. That's the only way to safely get it out 100%.
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done that with slants and found 1 inch of sludge! That is a lot!!
 
new engines with fuel injection arent as sludgy as an old carb engine.If you have a sludged engine take it apart and clean it its way past due :) Having wrenched on both because it was my time when carb cars went out and FI came in I can say this is true,when you remove a valve cover from an old carb engine ther ewas more sludge than a Fuel injected Ford Windsor.
 
They used to sell "engine flush" in 1 gal cans at auto parts thru 1980's. I used it once in my 1969 Dart 225 (Rislone, I recall). It was hydrocarbon solvents, similar to kerosene. You idled the engine with it in the crankcase for a few minutes, then drained. Maybe 1 year later, the oil lamp came on, then went off. Came on again a few months later. I had the engine rebuilt since other issues. I suspect the flush dislodged gunk which blocked the pickup screen. I would never use it again. If you think the pan is gunked and won't remove it, if you have time drain and pour in diesel fuel and let it sit for a few weeks then drain. Bio-diesel or vegetable oil works even better. You might use diesel-rated oil (CJ) in the future since it has more detergents.
 
Many years ago i had a 68 chevy pickup. It was sludged up so bad i couldnt pour a quart of oil onto it. I pulled valve covers, scraped out what i could. Replaced valve covers and poured in a quart of “gunk” engine flush. Kicked it up on the fast idle cam and let it sing for about 3 times the reccomended run time. Dumped the oil, and replaced the standard filter with a 2qt size without a bypass. Drive it a couple weeks and changed oil again. We ran it for years, then i installed it into a 77 jimmy and beat the snot out of it. It ran suprisingly well. I will say i got lucky. Would i engine flush again? Good oil pressure and no knocks, sure.

my 51 dodge flathead got the oil pan pulled 2x and cleaned. Its on its 3rd oil change in a couple hundred miles. 40 psi and runs mediocre. Figuring some oil additive would free up the rings in number six. Nah. Its coming out.
 
If the engine is running good leave it alone. That /6 has solid lifters ..sludge will not bother them.
 
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