Chemical flushing is not "bad" but in many cases it will not remove all of the crud and sludge. So you end up with areas where you still have sludge but now that sludge may be "loose" because the chemicals softened it. That could break free and plug a bearing oil feed or block oil flow to a camshaft.
Tearing it down takes more time and money but you can also check the parts, replace things like the timing belt or chain, water pump and gaskets. When it goes back together those parts that are "service items" are now done and you know the inside of the engine is clean.
Tuesday, January 24th, 2017 AT 5:13 AM