1997 Volvo 855 GLT Brake "Catastrophe" repair 1330273

[jreed]

I recently replaced the rotors, calipers and pads at the front on my '97 855 GLT at about 176K miles. Thanks to all the good info here on the site the job went pretty well, until near the very end I overtightened one of the guide pins that attaches the rotor to the hub, shearing it off.
I was using a torque wrench set to the 6 ft-lb specification, but I used a 3/8" drive 5-80 ft-lb wrench, which is right at the lower end of its range -- probably not accurate... I probably should have been using my 1/4" drive 20-200 in-pound (1.6 - 16 ft-lb) wrench instead. Lesson learned.

Sheared guide pin

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The sheared surface was pretty flat, which helps when getting it out. Note, I rotated the rotor to position one of the larger lug nut holes over the guide pin so that I could get better access for drilling and tapping:

Close up of sheared surface -- pretty flat, which is helpful

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To fix it, I got to get some new tools, which is always a good thing, including left hand drill bits, extractors, and a tap and die set. I've always been wanting an excuse to get some left hand bits and a tap and die set -- this was my chance!

How I fixed it:

Step 1: Strike a divot.

Strike a divot in the exact center (as close as you can get)

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Divot

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Step 2: Use left handed drill bits to drill a hole through the bolt (be sure the drill is set to reverse). I used left handed bits because there is a chance that the bolt will turn out and come free while you're drilling. I used a couple of sizes of bits, starting with a small one to make a pilot hole, until the hole was wide enough to fit the extractor.

Use left handed drill bit to drill hole through sheared bolt

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Step 3: Try the extractor (gently). If the bolt doesn't start spinning out freely with moderate pressure, don't force the extractor because if it breaks then potentially you would have a bigger problem than you started with. In my case, the extractor didn't budge the bolt. One problem with fluted left-hand extractors in general is that they are going to put pressure on the inside of the sheared bolt, pressing the remnants against the hole, which doesn't help when you're trying to turn it free. I guess they could work but in this case it didn't and I decided to switch to a tap instead.

Extractor

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Step 4: If the extractor doesn't work, retap the hole. In this case, the hole was originally tapped M6 1.0mm pitch, so I used my new M6 1.0mm carbon steel tap. Be sure to start perpendicular to the surface. I used some WD-40 as lube. Go slow and gentle with a tap, applying lube periodically and only turning 1/8 to 1/4 of a turn forwards before reversing to make clean threads.

M6 1.0mm tap

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Step 5: Clean up all the oil, shavings and swarf. I used a magnet, a rag and a good bit of brake cleaner spray to make sure all the shavings were cleaned out between the rotor and the hub, the lug bolt and guide pin holes, and that the brake disc was clean. Install guide pin in the newly tapped hole:

Install guide pin.

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Step 6: Reinstall wheel... this is what the brake job should have looked like the first time, and now it does:

Guide pin installed, wheel on.

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All's well that ends well.

[cn90]

Nice,

But many many cars out there don't have this guide pin.
I guess you could have left it the way it is.

The guide pin is Volvo engineers' crazy way of making sure the tire goes back to the same place.
However, it is a moot point once you rotate the tires, i.e., at that point you can no longer assume the same tire indexing any longer.

[mecheng]

Nice work. I thought I was anal, but ive never used a torque wrench for a guide pin. A bit of anti seize and just tighten until it stops, no extra force.

[confused_al]

I broke one of these years ago, as a lazy old guy I just pull the rotor and vise griped it out.

[scot850]

I agree with the tighten gently until snug approach. As someone that tends to over-tighten stuff, this is something that is not critical. Also, I thought there are 2 locating holes in the hub? Mind you, you can never have too many tools! Sometimes it is just satisfying to fix something like this. Had to do this with the front ABS sensors as someone had snapped one bolt off on one side and butchered the other side. Fixing those, while frustrating, were very satisfying.

Well done!

Neil.

[jreed]

This time when I installed the guide pin I just put a drop of threadlock on it and tightened it up finger tight... I didn't want to risk stripping the cleaned-up threads out of the hub.

[rspi]

What cn90 said.

I actually had a serious issue with one of those pins. Had the tires rotated on my 960. When the guy put the wheels back on he didn't know how to install the wheels, aligning the pins in the wheel and tightened the wheel wrong on ome of the pins. As soon as I hit the freeway I knew it. Had to pull over and pull the wheel and reinstall it in my suite on the way to an appointment (dirty mess). Bent the pin, cut into the wheel nippnipple, warped the rotor and made me late for my appointment. Cost Sam's Club about $700.

[jreed]

I agree with you and cn90 and would have left it alone, but the length of the sheared pin sticking up was enough to interfere with seating the rotor against the hub unless aligned. Down the road while rotating wheels or changing a tire somebody would have inadvertently let the rotor shift over the stub of the pin and then there would have been a good chance of warping the rotor.

[abscate]

I actually lube it, no Loctite, and just finger tighten it. If it comes out, it will just rattle I the little Space in the wheel, after all.

[skloon]

The heck with the uses of the pin I am amazed seeing someone actually being able to use a screw extractor, I usually end up snapping them off inside the bolt or cant drill straight down the centre, hats off to you