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Opel Junkie
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Discussion Starter · #1 ·
yes, it's me, with yet another headlight inquiry (i swear i will make these things work if it kills me!!)

i got the left light to roll over and latch both open and closed. upon installing the right bucket, i found that 2 of the 3 8mm head bolts are broken off in the holes. i need to know what size the bolts are so that i can tap them out, and what size drill bit to use. if it were standard (american or SAE) i could tell you just about every combination, but i am relatively new to the metric scene, and need some help.

again, i appreciate any help given.

mike
 

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Those have to be 5 mm. That would be 5 x .8. Your minor diameter is 4.2 mm and so is your drill size or .156 inch. Drilling very carefully on center of the broken bolt will take out everything but the threads. Leaving you to run a tap to clean out what is left in the threads. Just be careful about breaking a tap.

Minor is the diameter between threads, size - pitch = drill size. Pitches are equal in distance and depth of thread.

I live in a metric world
 

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Good advice by nobody (that sounds kinda' weird!). Once those bolts are broken off, it is a major PITA to fix a headlight mechanism. But I just had to figure a way to do it, and after some (many) failures, here's the best way I can suggest.

First, here's a photo of the front of the mechanism, with the small bolts shown. What makes it hard to fix is that they are not only an odd size (M5 x 0.8 with an 8 mm head versus the standard 9 mm head), they are also metric grade 10.9. Which is equivalent to an SAE Grade 8 bolt, so they are HARD. And damn difficult to drill out. What I learned was you can't drill them out from the front, as the remainder of the bolt will be pushed out the bottom of the hole and jam in the mechanism.
 

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So what you have to do is remove the mechanism from the car. Difficult, but it gets worse. You also have to disassemble the mechanisms, which aren't made to come apart. But with a bit of ingenuity, you can do it. First, grind the five rivet heads off on the BACK of the mechanism (NOT the front!) as shown
 

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Here's what a mechanism looks like when taken apart. OK, after cleaning.

You can also see the swivel pin latched into place (shown by the red arrow)
 

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Next, you need to remove the driven gear. It just pops out once you remove the swivel. Here's a view from the front
 

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But the trick here is to drill out the broken bolts from the BACK. The threads in the gear don't go all the way through, so you will never successfully drill the bolt out from the front. You also need to use a "cobalt" drill bit, as the grade 10.9 bolts are VERY hard. I found the best way was to use a drill press, set at very low speed, and use lots of pressure. Once the bit grabs the broken bolt, it just spins out the front of the hole. But if you wreck the threads, you are hooped. The gear is hardened, and I could NOT get a tapered tap to successfully re-thread the holes, even with very minor damage. And "nobody" was also correct in saying to be careful with the tap. I broke mine inside one of the holes I was trying to re-thread, and there is no way to remove the broken piece. A tap is WAY too hard to drill out, even with a cobalt bit
 

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Once you get the holes cleaned out, get new M5 grade 10.9 bolts (my speciality bolt store had them, but NOT with the 8 mm head) and make sure they go in far enough to tighten the swivel pin against the gear. I found I had to shorten a couple bolts to allow them to be tightened before they bottomed out on damaged thread.

Also make sure the mechanism is working properly before you reassemble it. Here's a photo of how the pin latches into place, and how the drive gear pushes a release latch, allowing the pin to be released.
 

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Finally, reassemble the mechanisms, making sure they are clean and lightly greased. To hold the two halves together, I think the best way is to place a small weld (preferably a MIG welder) over each of the removed rivets. Make sure that the halves are properly aligned and completely together before you weld them up.

HTH
 

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Opel Junkie
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Discussion Starter · #10 ·
i measured the bolts today at work, and found that they are actually 10-32...does this sound right, or has someone already replaced them? opinions?
 

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nope

Probably the only time in history that a metric bolt and an SAE bolt are the same size is the m5x.8 and the 10-32. They bolt to each other both ways, and they measure out almost exactly the same, but your bolts are probably still m5's. Very hard to find a hard 10-32 bolt, though, so you probably want to stick with the metric stuff.

Most car stereo's have this size bolts on the side too, that's the only reason I ever found out.
 

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I have found much success with removing snapped off screws by drilling a small (1/8 - 1/4 wide and 1/2 inch deep) starter hole in the damaged screw shaft. Then use a reverse threaded drill bit (slightly wider than the original one used to drill the pilot hole) to unscrew it from the hole. Works on manifold, header, and starter bolts.
 

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Keith, et.al., The only way I've found to remove an easy out or a tap was with a Dremel and a very small carbide cutting bit. Used that setup to remove a broken easy out from my mother's 66 Comet Caliente water pump bolt. A real PIA, took a long time to grind out the busted easy-out but perserverence paid off. Also if you have a machinists friend with a good assortment of tools, there are tap removal tools that will remove the broken taps by sliding fingers down the flutes of the tap and will assist in twisting them out. I've seen them in 3 and 4 finger configurations. 10-32 ? I'll have to check that out. I think I got the last bolts OGTS had and they were used. One thing about the original bolts, they have a shank with no threads about a 1/4 inch before the threads start. 10-32 allen bolts can be had in the aircraft industry that are grade 8. I use them on my model racing boats. They are also available in stainless steel but are a little softer than the grade 8s.

Ron
 

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I have a small supply (about 50 +/-) of a 12.9 grade socket head cap screw of the correct size and length, if anyone has trouble finding some.
 

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BQS4,

If you still have some of these bolts I could use at least three of them.

Here is the situation I found with my passenger mechanism; The headlight bucket was over rotating. When I took the cover off the light, there was only one bolt in one of the three holes. When I tried to screw that bolt into the other three holes, it wouldn't go. My assumption is that the original bolts broke off and need to be drilled out.

My question is, how hard and time consuming is this operation? Seems it could be the better part of a day to complete this.

Also, Would it make good sense to pull both out to clean them up, if I have one out?
 

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houserc, I would suggest doing them one at a time, you could pull the headlight cover and use it as an example of what it should look like as the other side goes together. I recommend doing the same on the rear brakes, a physical pic is a lot better than the written word.

Ron
 

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My assumption is that the original bolts broke off and need to be drilled out. My question is, how hard and time consuming is this operation?
Read the posts above, especially my post regarding drilling out the old bolts. To have a reasonable chance of drilling these hardened bolts out, you really MUST remove and disassemble the entire mechanism. You will need a drill press. And do both while you are there. Count on an entire day. Good luck!
 

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My driver side headlight 'bounces' back up about 1 inch after I open the headlights, causing neither light to come on. If I get out and manually push it all the way back open the lights come on.

Is this caused by a similar problem as mentioned above or is this a totally different adjustment to fix? I looked at the light and it appears the latch mechanism on the drivers side light is not 'latching' open for some reason. Is the mechanism shot and needs replaced possibly? Or is it fixable/adjustable?

Thanks guys,
Claud
 

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Claud, the latching mechanism contacts a micro-switch and turns on the lights. If you driver's side light is not latched open the lights will not turn on. That's usually caused by one of two things, either the bolts holding the spring plates to the rotating mechanism are loose/broken off or the spring plates are broken. The spring plates attach the headlight buckets to the rotating mechanism. The latching mechanism can be lubricated to operate more freely, but I suspect something is loose or broken inside the headlight bucket, but it can be fixed using Keith Wilford's instructions.

Ron
 
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