|
Hey I pulled this off the Austin America site in US, it makes sobering reading.
Kevin G
Thanks to Todd Miller!
Engine "Flush" treatments:
-This was a recent topic on our 1100 email chat group and I thought it an important one to save for future reference. It began when one of our members took their all original car to their mechanic for a "routine" oil change. The car's owner supplied the oil and filter so all the shop had to do was the labor.
Upon removing the drain plug and finding the usual metal shavings on the magnetic end, they told the owner that the engine really needed a good flushing to clean out all the crud inside. The trusting owner agreed.
The shop left the old filter in and filled the engine crankcase with diesel fuel and some oil. They ran the engine for a bit, then drained this out. Still leaving the old oil filter in, they refilled the crankcase with Automatic transmission fluid and some oil. Again, ran the engine for a while and then drained this mixture out. This time, they replaced the filter and put in the owner's supplied Castrol GTX 20w/50.
The engine now has only about 35psi oil pressure warm going down the road, and about 15psi at idle.....prior to this it had 25psi at hot idle, and probably 50 or so at speed.
So, a day late and a dollar short for this owner, here is my 3 cents worth on engine (and transmission) flushes:
-All the engines got the magnetic drain plugs. And, for good reason! Look at all the stuff they catch!! I wouldn't sweat the metal pieces too much. They all do it to some degree and it's just another reason to change the oil more often.
Naturally, there is some suspended crud stuck to the walls of any engine. More so in engines that don't receive regular oil changes, or just get driven around town so the oil never heats up enough to burn off all the impurities. The last thing I want to do is flush
all this stuck crud, down through the engine. Why? Because where does it go?
First, it gets sucked up and run through the oil pump vanes. Guess what that does to the tight tolerances in the oil pump as the vanes get scored. Next it goes past the oil pressure relief valve and can score that piston so it doesn't seat properly. Then at trip through the oil filter where hopefully all of it is caught, and hopefully the oil filter bypass doesn't open due to all the crud that's moving through. If the bypass opens it dumps all this crud directly into the crankshaft and camshaft bearings. On top of all that, the crankshaft and transmission gears sling all this unfiltered crud up onto the piston walls so the pistons now have a chance to drag up and down in it.
Oil pressure is all about tolerances...and keeping them small. Tolerances in the oil pump vanes, tolerances in the crankshaft and camshaft bearings, etc. Once those tolerances start to get big...indicating wear/damage...the oil pressure starts to suffer big time. For example, the crankshaft bearings run on a tolerance of .0015"-.003" By comparison, a sheet of paper is .004" thick. That's why I freak out when I hear about engine flushing. Imagine the diameter of the crud particles (mostly chunks of carbon, which is quite hard) that are being flushed around and they go through the oil pump completely unfiltered. And, if that's not bad enough, oil filters have a bypass function so that they won't clog up and stop oil flow. So, potentially if an oil filter got hit by a boat load of crud, the bypass could open up and allow everything to bypass the filter.......next stop, .0015" clearance at the crankshaft. Ouch!
So, in my opinion, whom ever invented engine flushing (and likewise automatic transmission flushing) is the same guy who wants to sell you a $4,000 engine rebuilt about 6 months from now. And, that's probably the same guy who will say, "Well, that engine's 30 years old, it's probably all wore out inside," when you come back 4 months later asking why it's knocking and has low oil pressure at idle.
But hey, call me paranoid. I say leave sleeping dogs lie.
On the flip side, if oil is getting black before the usual 1,500-3,000 mile oil change interval, then consider changing it more often, do less low speed/short trip driving, and have the carb mixture checked to make sure it's not too rich.
Todd
_________________ DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. 
|
)
