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Broken Fasteners


Selden

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With 120,000 miles approaching, I'm starting the annual teardown.

 

— Run for 15 minutes/15 miles to heat up all the fluids

— Drain FD oil

— Remove belly pan

— Remove right fairing

— Drain transmission oil

— Drain engine oil

— Remove remaining bodywork

— Remove valve cover guards

 

The last step is where the trouble started. I've done this at least 10 times, probably more, in the past 50,000 miles, but this time the lower engine guard bolt was frozen in place — on both sides! The front an rear bolts came out easily, as expected. It's a mystery why these bolts decided to freeze at 120,000 miles, after being removed every 5,000 miles since 2009 when I did my first valve adjustment. I'm usually pretty careful when I disassemble things to put the same bolts back in the same holes, so as not to lose them, or mix up bolts of different lengths.

 

I could tell by the amount of force I had to exert that they were going to snap off, but there really wasn't any choice, other than sawing off the bottom of each valve cover guard.

 

Perhaps if I had heated up the engine before trying to remove the bolts they would have come off easier, but what's done is done.

 

Left (broke off flush):

Left.jpg

 

 

Right (protrudes about 5mm):

Right.jpg

 

My question is this: Is is better to do nothing, or try to drill them out? I could probably get a pair of vice grips on the right hand bolt, heat it up and turn, but there is no guarantee that it would come loose, and doing so might make drilling it out more difficult.

 

It's not the easiest place to work in, and as far as I can see the sole point of these threaded holes is to provide a lower mounting point for the valve cover guards. If they provide no significant tightness for the base of the cylinder heads, I'm inclined to leave things as they are.

 

What would DR do?

 

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What would DR do?

 

Afternoon Selden

 

That's a darn good question.

 

My hindsight answer would probably be-- I wouldn't have twisted the bolts off to begin with. Once I knew the bolts would twist off before loosening (you all know the feeling of that) I would have just drilled the bolt heads off-- (at least that gives me straight studs to deal with. (then probably just weld a nut to the stud as the welding heat is usually enough to loosen the stuck bolt)

 

As a rule my standard way to removed broken bolts is to weld a washer to the broken bolt through the center washer hole, then weld a nut to the welded on washer. Then allow to cool for a minute or two, then simply unscrew the broken bolt using that welded on nut.

 

From the picture that you show & the fact that those bolts don't go into anything structural or important my other option would be to carefully (& very straight) core drill the flush broken side with successively larger L/H drill bits until I get to about 5mm. That should (either) get to proper tap size or hopefully back the broken bolt out on the left hand drill bit. (I would do the flush-broken-off side first)

 

On the side with the bent extending bolt I would see how the first side came out. If it drilled out easily & came out or allowed a good clean re-tapped hole then I would grind that bent portion off & do the same as the other side.

 

If the first side was a pain then I would try heating the bent bolt as hot as possible (without damaging the surrounding areas) then try a pair of "butcher pliers" (AKA Vise Grips) to see if it would come loose that way. Otherwise either drill it out or weld on a washer/nut.

 

Added: I guess if things go wrong then just drill the entire broken bolt all the way through with a small (easy to control)drill bit, then drill all the way through with a 6mm drill bit, then use a longer bolt with a nut on the back side to hold the guards on.

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Thanks, DR. Hindsight is usually 20/20, and I was thinking the same thing. Back to one of my questions: It looks like the two large cap screws at the bottom side of the cam chain area are what are primarily holding things together. I just stuck a mirror behind, and confirmed that the hole goes all the way through, so, assuming alignment, it would be fairly easy to drill out the fasteners, as you say, using progressively larger bits, then either a screw extractor, or just retap.

 

Cylinder%2BBarrel.png

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Thanks, DR. Hindsight is usually 20/20, and I was thinking the same thing. Back to one of my questions: It looks like the two large cap screws at the bottom side of the cam chain area are what are primarily holding things together. I just stuck a mirror behind, and confirmed that the hole goes all the way through, so, assuming alignment, it would be fairly easy to drill out the fasteners, as you say, using progressively larger bits, then either a screw extractor, or just retap.

 

 

Afternoon Selden

 

I'm pretty much against screw extractors (if it won't travel through on a R/H drill bit or back out on a L/H drill bit then it probably won't come out on a screw extractor.

 

Those darn screw extractors expand the broken bolt so if much force is needed about all they do is expand the broken bolt & make it tighter--THEN-- the darn screw extractor breaks off in the stuck bolt.

 

Those things (screw extractors) are harder than snail's nuts so if you break one off you have REAL BIG problems.

 

 

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I had a summer job in Ann Arbor working for a company called "Electro Arc" that made equipment for the auto industry that burned out hardened tool bits from whatever they were embedded in.

 

I tried the heat (up to ~200° as measured with a pin point instant read thermometer) and vice grips approach, but it didn't budge, even after I ground flats on the sides of the screw to give the vice grips a better grip. I then used a cutoff wheel to cut off the end of the bolt and give it a flat surface.

 

Next step will be finding some left-handed drill bits, but I'm having a hard time finding them, except through Amazon. The choices seem to be titanium coated M2 steel or Cobalt. My experiences with Chinese-made drill bits has not been good. Irwin seems to have the best ratings of what I have found. Any other suggestions?

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Afternoon Selden

 

Use a mirror & look behind that screw boss. I believe it is threaded all the way through. If it is then you can probably just use standard R/H drill bits as it (hopefully) will catch & run the bolt all the way through.

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Charles Elms

Not to be flippant, but do you really need valve cover guards at 110k. After my 97 RT hit 90K miles I didn't bother putting mine back on after valve checks. Didn't drop it after I removed them.

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Not to be flippant, but do you really need valve cover guards at 110k. After my 97 RT hit 90K miles I didn't bother putting mine back on after valve checks. Didn't drop it after I removed them.

 

It's the principle! Approaching age 70, a parking lot drop becomes ever more likely.

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Hint - Start drilling with a very carefully centered, sharp, very small dia drill bit - like ~3/32" dia. Then drill/ream with progressively larger bits until you get to one that is close to the minor diameter of the thread.

 

I find it is so much easier to control a small dia bit. Good luck!

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In the future, I would hit it for a couple of days with Deep Creep. A penetrant that dissolves corrosion prior to loosening. You could try this on the bent bolt before your vice grips.

 

If you are constantly removing these bolts, I would also suggest that you replace the bolts with the proper metric size in stainless steel. (less reaction with Aluminum than straight hardened steel bolts and you are not going to lose much in bolt strength.) The reason they froze now rather than earlier more related to corrosion since just a thin plating of surface metal to resist corrosion may have finally worn off the bolt threads. Had you replaced the bolts every 3 or so years, it would have been less likely to have happened.Cadmium plating is used on aircraft bolts for anti-corrosion (gold color)

 

If you are going to drill the bolts, use a flat wheel grinder or the side of a cut-off wheel and carefully level the drilling surface. I would also hit the bolt dead center with a hardened center punch to make an indent so your drill does not wander. The one bolt broken off below the surface , all you can do is center punch since you can't reach it to grind without damaging the cover.

 

Welding the washer and a nut to the remaining stud works well if there is enough stud exposed to do it. The heat will expand the Aluminum faster than the steel and reduce the oxidation helping to free it up.

 

Push come to shove, you can drill out the bolt , rethread the hole and insert a Heli-coil allowing for the same sized bolt to be used again.

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I'd start fastening the valve cover guards with only two screws instead of three, and I'd use a little anti-seize. In fact, that's what I'm doing now on one side.

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I decided to tackle the right side (the one with the protruding threads that I cut off yesterday) this morning. Tedious, but all in all not too bad. A center punch got the bit started pretty close to center, and bit by bit, I made the hole larger, stopping at 7/32". One bit snapped, but since the hole went straight through, I was able to push it out from the back side.

 

The real challenge was figuring out how to tap the hole, as there is not enough working clearance for a traditional tap handle. Being a pack rat has real advantages, and at least a decade ago I saved some square-section steel tubing. I jammed the tap in one end, then used the center punch to pinch the tubing against the four flats, and voilà, new tool:

 

TapWrench.jpg

 

 

Two other things came in really handy:

 

1) Headlamp with focusing beam:

 

wolverine.jpg

 

2) I had cataract surgery 3 years ago, and while my distance and night time vision have improved by leaps and bounds, working on things close up is a chore, and over the past 3 years I bought readers in 1.0, 1.25, 1.5, 1.75, 2.0, and 2.5 strengths, depending on the task at hand. A couple of months ago I found a pair of varifocal readers, which have changed everything. I no longer lose my glasses, because I don't need to take them off as often, and I can focus on almost anything at a reasonable working distance by looking through the appropriate part of the lens. Coated optics, decent frame,

 

I plan to attack the left cylinder tomorrow.

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Left cylinder finished, easier than the right because I started with a 1/8" bit, rather than the 3/32" that I used yesterday. Cut faster, with less risk of breakage. Both holes came out very near dead center at both ends. Everything else should be downhill from this point.

 

Thanks for all the advice guys — especially for the observation that a left-handed bit is unnecessary for a hole that goes straight through. On neither side did the stuck fastener spin out. I have no idea what happened, but when I put things back together I'm going to put a couple of turns of Teflon pipe joint tape around the threads.

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No problem: the melting point for polytetrafluoroethylene is 620°F, and that part of the engine probably never gets above 180°, if that.

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