$#!!!T% I overtightened a coil pack bolt

quoting yourself now chap? that's so 1990's.

 

It's just amazing when you consider that none of us, absolutely none of us, has ever done anything like that before!

-Chap

 

I think this is the part I am not understanding. Is the bolt head tight against the flange ?

 

Yes. The purpose of the bolt is to hold the igniter tight against the valve cover so that the rubber O-ring will seal the spark plug well against water dripping in. However this is not a great design.

Some owners experience engine misfire issues when water manages to get into the spark plug wells. That moisture allows the high voltage applied to the spark plug to dissipate to ground instead of sparking across the plug gap.

 

^^ Thanks Patrick, but I am still stuck on the broken bolt that came out easy

If the bolt head was ~ flush with the flange, why was there a bit of broken bolt sticking out above the flange ?

 

The remains of the broken bolt slightly protruded above the valve cover. The igniter and its flange had already been removed by the OP prior to his taking the photo. Fortunately the OP was able to grab the bolt shaft and unscrew it.

 

so the head was compressing against the ignitor, and unable to go any further, thus shearing off, while the threads were still loose.

 

They weren't very loose while the steel bolt was being stretched to the breaking point. But they were loose again right after, because the part that had been pulling them upward was now in the frustrated OP's hand.

SageBrush, don't forget that igniter flange is like ~ 10 mm thick. There were 10 millimeters of bolt shank in between the head on top and the threads into the valve cover below, doing nothing but being a twisty (steel) rubberband. It snapped somewhere in that region.

-Chap

looking at this again "shearing off" may not be the best way to say it, because 'shear' has a specific meaning of a sideways force that wasn't in play here. The bolt shank was pulled apart by the combination of: twist, and tension exceeding the material's tensile strength.

 

right. a lot of tension, and then

 

never mind, until I color a photo ...

 

I know I haven't. I am quite incapable of producing that amount of torque with a regular sized wrench

 

Doesn't take much torque to break an M6. Specified torque values are typically within a not-ginormous safety factor of what would actually break the bolt. If 6.8 ft-lb was the spec, the OP may have been planning for 82 but probably never exerted more than 15 ... hard to keep straining on that handle after the bolt breaks....

-Chap

 

Consider getting an inch-lb microtorque wrench. Remember, torque wrenches are most accurate in the mid range of their given range, less accurate at their extreme low and high values.

You have learned a good lesson the hard way, and won't be making this mistake again.

Fortunately, everything ended well.

 

You saved me a bit of typing. I just did EXACTLY the same thing - doubted the number, but trusted I was smart enough to set up my shiny new torque wrench correctly. Now, I have half a bolt and no way of getting the end out easily.

2004 with 240k - second plug change - huge gap after 120k on the last set. The car runs great after putting in my new plugs, but the #1 coil is not secured down.

With the clearance available, center punching or left-hand drilling the piece down in the hole is going to be rather difficult. Is this something a dealership deals with themselves and would they be able to extract it quickly enough? I can pull the valve cover easily enough, but really don't want to get that deep into it. I'm already almost over my head replacing the bumper guard and plastic shields under the engine after hitting debris on the highway. I figured I was overdue for plugs and it was easy to get them done while I had the car apart. Silly me.

Any other ideas on how to extract a recessed remnant of a bolt or whether it's okay to ignore it and trust the rubber sleeve will keep the coil in contact with the plug?

 

Wander your local hardware store looking for a right-angle adapter for your favorite electric drill. That may allow you to sneak a drill bit onto the bolt fragment with less clearance trouble than you think. Also, Dremel makes a right-angle adapter for their moto-tool, even skinnier than the typical one for a regular drill.

People reportedly have troubles with water getting into plug wells even when the coil is properly snugged down, so I don't think I'd want to try to do without it.

-Chap

 

Dude, I had the same thing happen to me today! x 2 no less. I was very lucky as I was able to get the remnant part of the bolt out. Ran down to the Home Depot and got some 8.8 metal machine screws zinc coated believe they were M6 x 1.0 ?? Anyway, called Toyota and had them order me up 4 bolts, and should be at the stealership in a few days. I was using a torque wrench, because I read/ heard/ watch something to the effect that both the plugs and coil pack bolts get 13ft/lbs. To hell with that, I am definitely going by feel this time. Anyone know the real torque specs for these bolts? I seriously thought that I was going to have a heart attack in my driveway! I was thinking for the next bolts a smiggen of blue thread locker on and just snug them up. Please, anyone with more knowledge on cars let me know. I am more of a construction guy than auto guy. Thanks in advance.

 

The OP snapped it off while tightening it to 80 lbs. Then how was he able to take it out with just his fingers?

 

Torque is 80 inch/pounds.

With small locator bolts like this I would just go by feel. A screw driver with socket drive on it is good, or treat your ratchet wrench like a screwdriver: hold it one-handed over the center when tightening, and just snug them.