The 5 Most Basic Mechanical Mistakes that can Plague Any Project
Think you know the 5 most basic mechanical mistakes? You probably do, and you probably still make them anyway.
1. Too Tight
If these sound really basic to you that's because they are really basic. Pesky human nature keeps us doing the right things the wrong way. As kids, we learned how Bugs Bunny could make a wheel come off the Coyote's rocket bike, and ever since then the fear that something might come loose and kill us has been whispering to us 'Tighter, tighter.' Drain plugs, lug nuts, oil filters, rocker locking nuts—all things that make you nauseous when you imagine them coming loose, all stuff that is routinely over-torqued. Sure, we all follow torque specs for head and main bearing fasteners, but every combination of metal, diameter, thread pitch, length, depth, and heat range has an ideal tightness it likes. Go past what it likes and metal will pack it up and go home. And metal will often tell you what a torque wrench won't. Lots of people snap studs off or pull threads out using a torque wrench. Pay attention to how soon a fastener gets tight or if it doesn't ever get tight enough. Metal rarely lies to you.
2. Too Loose
Okay, so this isn't a thing. Not really. Sure things wear out and need adjustment or replacement, but that's a wear issue, not something we make happen on purpose. Mechanics and technicians are by and large a pretty macho group (you too ladies) and not generally known for wussing out when it comes to tightening things. For instance, you tighten a loose fan belt extra tight so it stops slipping and next thing you know your water pump bearing is adios. Similarly, tighten your carburetor down more to fix that vacuum leak and you'll warp that soft pot metal even more and the leak will get worse. Ditto for cam covers and oil pans. In fact, the major too loose danger zone is zero torque, as in you forgot to tighten that nut at all. Now that's a problem. Making a list and checking it twice is a great solution to the problem of remembering to do things, and so is paint. Manufacturers and plenty of race teams use paint markers on a fastener to show that it's been torqued down correctly. We'll allow that parts do come loose but, used correctly, lock and spring washers, nylocks, prevailing torque nuts, jam nuts, cotter pins, lock tabs, safety wire, and the miracle of Loctite are all here to save our bacon.
3. Too Dirty
This one probably should have been first except no one is trying to make things dirtier so we're not fighting human nature here. Nothing works right if it's dirty (corrosion counts as dirt too). Sealant won't seal dirt, bearing surfaces don't like to spin in dirt, parts don't want to press into dirty holes, valves can't seal against dirt... the list goes on and on. That's common knowledge. The dirt that gets us is the dirt we can't see. And dirt isn't as easy to see as you might think. If you didn't clean something right before you assembled it then you assembled dirty parts. You can even clean something and it turns out it's not clean after all. You can pump gallons of solvent through crankshaft oil passages, hold paper towels in front of them and force compressed air through them and nothing but clean solvent blows out the other sides, but drill out the oil passage plugs (if your crank has them) and run a drill bit down the bores and you'll find hard goo that you didn't know existed. Don't look for clean, look for dirty. Look everywhere.
4. Too Backwards
'Too Wrong Order' didn't sound right, but that's what we mean. You can't always tell it from first glance but most parts that fit either way around only work correctly when installed one way. Piston rings, connecting rods, bearings, even many washers have chamfers that need to face the right direction or else bad things will happen. Read the directions even if you think you know which side is up; new parts often have different design specs than the ones they are replacing. And don't be embarrassed if you don't know how everything you took apart 6 months ago goes back together—just look at those pictures you took. Same goes for that brake caliper you took apart 30 minutes ago.
5. Too Lost
Have you ever seen how many parts a car has? So many! You can only work on a few at a time so put the other ones away. If you want to lose parts, or get them covered in filth and rust, leave them sitting out. If you want to keep track of parts, do what you do with your keys: put them back in the same place every time. 'Everything in its right place' is more than just a great song. If the worst does happen, you looked everywhere but you still can't find that missing part, follow my personal rule: Look the first place you looked, only harder. I guarantee, 90% of the time that's where the lost part is hiding. You expected it to be there, but you were in a hurry and when you didn't see it right away you gave up and started looking other places. Trust me, it's there.