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Showing results for tags 'aluminum oxide'.
Last night I watched a video of a Ford mechanic recommending Scotchbrite Roloc bristle disks of various grits and actual Scotchbrite pads to clean the headgasket mating surfaces on both the block and head. . He knew what he was doing was controversial and stated so and even turned off the comments on the youtube video he presented to avoid negative comments. The video made me think about what the guru, bbobynski, use to say, "keep scotchbrite far away from engine work" because it is way more abrasive than you realize, the aluminum oxide particles get into the bearing clearances and eat up the bearings and journals. That has always stuck with me and I cringe when I see mechanics use scotchbrite to clean mating surfaces. Well I did a search and found valuable info that bbobynski posted on the subject, I was very happy to find it. Here is bbobynski: Someone in another thread mentioned using scotchbrite to clean up gasket surfaces during an engine rebuild.....not a good idea.... Scotch brite.......!!!!............????????? NEVER USE SCOTCHBRITE TO CLEAN UP GASKET SURFACES OF AN ENGINE. NEVER, EVER, EVER USE SCOTCHBRITE ON AN ENGINE. At least not one you want to run again for a long time. Scotchbrite seems so benign but it is death to engines. Scotchbrite pads are nylon fibers with 40 micron particles of aluminum oxide in them. Scotchbrite dust leaves behind all those 40 micron particles hidden everywhere. Aluminum oxide is an extremely aggressive abrasive. It imbeds in the bearings and eats the crank....and other things. Scotchbrite is the bane of the aftermarket re-man engine industry. There are lots of "new" re-mans ruined by cleaning up the old parts with scotchbrite pads and then installing them. Eats up the engine immediately. That is why many engines fail the main and rod bearings after a head job or other work...scotchbrite. People think it is because of coolant getting into the oil ruining the bearings or something when it was really the scotchbrite the mechanic used to clean up the parts... especially a Northstar engine where the block deck surface cleaning funnels the scotchbrite dust down the oil drain back passages. If you cleaned up parts with scotchbrite you now have a HUGE cleanup job ahead of you cleaning up after the scotchbrite. You must make positively sure that none of the dust remains anywhere on any parts or got into the oil cavity. Hopefully the valley of the engine was covered if you used scotchbrite on the deck surface as if it drifted into the valley or into the pan your engine is toast. I am very very serious about this. Scotchbrite has a very bad reputation in the industry as it seems like such an ideal cleanup method, seems so benign, yet can cause such extreme damage. Most mechanics in the know stay miles away from scotchbrite as it is harder to clean up after it than any labor it saves. If you doubt this at all call JASPER or any of the main engine re-man companies and ask them if it is OK to use scotchbrite to clean up the manifold you are going to put on your Jasper re-man... ANYTHING is better than scotchbrite pads or polishing discs. I have seen a LOT of engines ruined this way with aluminum oxide contamination from scotchbrite pads. Many field return cores of brand new re-man engines that were returned to the re-man center had bearings fail due to the mechanic cleaning up the old intake for installation onto the re-man long block with scotchbrite and then not cleaning up sufficiently. I like a razor blade scraper and some sort of chemical gasket remover to soften the old gaskets. Just do NOT let scotchbrite get anywhere near the engine or use scotchbrite in the area so that the dust can settle in the engine unknowingly. When the aluminum oxide particles get into the engine they are too large for the bearing clearance and imbed into the soft bearing surface due to the pressure of the crank journal. The bearing will look perfect, absolutely perfect...and the engine will actually run fine for quite a while. Right up to the point that, due to heat/load/RPM the oil film is pressed so thin that the peaks of the aluminum oxide peek thru the oil film and touch the crank....and start machining it down. In 20 minutes the crank journal will feel like a phonograph record surface yet...THE BEARING WILL STILL LOOK PERFECT. You would have to look at the bearing shell under and SEM to see the abrasive particles imbedded into the bearing. Run the engine harder and at more RPM/heat/load and the grooved up bearing looses so much load capacity that it starts to eat into the bearing shell surface due to metal-to-metal contact due to the oil film collapsing becasue the surface area of the grooved surface has been destroyed. THEN the bearing shell looks grooved up...but this is right before it seizes up/spins a bearing and puts parts thru the side of the block. Trust me, I have seen this exact failure mode many many times as scotchbrite is a favorite "tool" of the unknowing. Often, when a reman or repair fails the mechanid blames the reman or the "glycol in the oil" or whatever never knowing that it was the scotchbrite pad he used to clean up the manifold surfaces before reasembling. Reference Credit: I want to thank Bob is the Oil Guy for saving these words by bbobsyski. http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=563163