Slideshow: Most Commonly Overtorqued Items?
From brake bleeders to lug nuts, caution is the better part of valor when it comes to torque. We present this handy list to remind you of what you already know—because we forget so easily.
Brake Bleeders
Also referred to as bleeder screws, brake bleeders have been a source of woe for shade tree mechanic and expert technician alike since the dawn of hydraulic stopping systems. They've always been a royal pain in the throne to remove due to a magic combination of ingredients that includes: corrosive fluid, direct contact between dissimilar metals, extreme temperatures, and minute hexes located in hard-to-reach places. Even when bleeders haven't rusted into place they're a challenge to get off, often requiring a little blue-tipped wrench (torch) action to help coax them out of their wheel cylinders or caliper homes.
Motivated by a common culprit on our list, too much torque is applied to bleeders as a misguided fix, or out of fear of, a sealing problem. Bleeders seal on a taper, meaning they only have to contact corresponding taper to seal. But they have to contact it evenly and all the way around. Any dirt, corrosion, pitting, scoring, or warpage of either the concave or convex tapers will leave you with a leak. Overtorqueing a bleeder, if it doesn't snap off (the horror!), will almost always have the opposite of the intended effect. Force won't stop a bleeder from leaking, only smooth, clean, concentric surfaces will. It's not practical to completely remove a brake bleeder when you're just doing a simple bleed, but if you have a leak the best way to prevent it is to closely inspect both tapers, and make sure the surfaces are completely free of debris. It's always a good idea to have spare bleeders on hand, once a bleeder’s taper has been compromised it's easier to just replace it than to repair it.
*Note: all of this goes double for brake line fittings and flares.
Alternator/Accessory Drive Pivot Bolts
When people are tightening their vehicle's drive belts, it just seems a lot easier to crank that pivot bolt/nut together as hard as possible to hold the alternator, or A/C compressor, or whatever in place, until they can come back and tighten the bolt that goes through the slotted bracket—the one that is actually meant to hold the item in place. Don't do it. It's like the five-second rule with dropping food on the floor. Too far is too far, even if it's only for a few seconds. When done enough times this will result in a snap, crackle, or pop of the part you least want to break.
Hose Clamps
Similar to bracket pivot bolts, adjustable hose clamps are another item that begs to get the 'tighten one click too far, then back off a smidge' treatment. It's not a lap belt, it's a hose clamp, and tightening it until it jumps a slot will frequently deform the clamp enough so that it won't hold tension as it should. Unlike some of the other items on our list, sometimes tightness is the solution when it comes to a leaky hose-to-pipe junction, but if you hear that pop toss the clamp out and start over again with a newer or stronger clamp.
Drain Plugs
Drain plugs, especially oil pan drain plugs, are innocent victims of criminal over torquing. It's fear as much as ignorance that fuels this vice—no one wants to be responsible for an engine oozing away it's lifeblood. Since oil changes are one of the most basic maintenance operations, it's often those with the most base-level know-how that perform them, both as owners and as beginning techs in grease-and-gos. Like with bleeders, a clean, smooth, flat sealing surface is important, but unlike bleeders drain plugs can get a little help from a sealing gasket. Use a new one every time. It beats stripping out the threads in your sump by a mile.
Cam/Valve Cover Hold-Downs
Gaskets are also the key to keeping oil on the right side of your cam/valve covers—that and a little strategically-applied silicone sealant. Of course it's hard to seal a warped cover, so the cover's flatness should be checked, and of course, it goes without saying that mating surfaces should be clean (and dry if you expect any sealant to stick where you put it). What does not help is over-tightening those poor tiny nuts/bolts that hold the covers down—by doing so you may not strip or crack anything, but you are sure as heck going to warp something. Again, excessive torque=worse leaks.
Oil Pan Nuts/Bolts
Let's repeat that: excessive torque equals worse leaks. It's worth repeating because it's the same story on the other side of the engine from the cam/valve covers. Except there tends to be more oil at the bottom of the engine, so in some cases, more sealant is called for. Not more torque.
Lug Nuts/Bolts
Like an engine puking its oil out past the drain plug, a car jettisoning a wheel is the stuff of nightmares. And also like drain plugs, fear, and overzealous ignorance lead to messed-up parts. Those pit crew people spinning on lugs with air impacts at NASCAR races are highly trained, and their wrenches are calibrated. Plus they're sort of in a hurry. You shouldn't be in that much of a hurry to put on a wheel. As with all things, observe manufacturers' specs when torqueing down wheel lugs, and when in doubt pick up a cheap click-type torque wrench for doing the honors. For every lug you don't snap off your life gets extended by one hour. It's science.
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