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Discussion Starter · #1 ·
Many thanks to all for some time, I was encouraged to do my TB, water pump, pulleys, even did spark plugs and a couple other things....or began. On the last of 5 bolts on water pump, bottom bolt twisted off 1/3 down from head. I should have known something was not right because this bolt got put in wrong, crooked or mis-shaped at the factory because every other one twisted out by hand after initial break. Everything is else if perfect and now I have to figure out how to get remainder of a bolt out without doing more damage. Considering asking a former Firestone buddy to lend a hand, may either spray with penetrant, heat it up and use vice-grips try and turn, but it was stuck, possibly cross-threaded. It's good to step away for a day or so since I can use my wife's car. Crank bolt, no problem with Harbor Freights Bauer 8.5 unit, spun right out. Got the motor mount off by taking ECM and related attachments off, Fortunately the water pump is off, revealing more of the bolt teeth. Part of me doesn't want to even touch the thing. Ug!
 

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As your fellow Akronites famously sang...

 

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I'd keep putting PB Blaster ot Liquid Wrench on it, that is if you can still get a pair of vice grips on it, to try and get it turning. There a good chance it will need to be drilled out and tapped.
Sorry for your pain.
 

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If there's enough thread sticking out you could use a bolt extractor. Its a socket that grabs whatevers left. Usually sold at local autoparts stores.
 

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If there's enough thread sticking out you could use a bolt extractor. Its a socket that grabs whatevers left. Usually sold at local autoparts stores.
The one I found at AutoZone is to large to fit on the stud of what's left of a twisted off 10mm bolt. I couldn't find a smaller one. It's difficult to find one because even though the description claims to work on a 10mm, obviously that with the bolt head still intact.
 

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The one I found at AutoZone is to large to fit on the stud of what's left of a twisted off 10mm bolt. I couldn't find a smaller one. It's difficult to find one because even though the description claims to work on a 10mm, obviously that with the bolt head still intact.
Yeah they can be hit-or-miss tbh. Id start with heat, then spray it down and try with a good set of vice grips. Luckly they arent torqued to a crazy spec.
 

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The one I found at AutoZone is to large to fit on the stud of what's left of a twisted off 10mm bolt. I couldn't find a smaller one. It's difficult to find one because even though the description claims to work on a 10mm, obviously that with the bolt head still intact.
Keeping in mind... Bolts are sized based on the diameter of the threads, not the size wrench used to turn it. The water pump bolts are 6mm with 10mm flanged hex heads. Shop for a stud extractor for a 6mm size, and you should be OK. Try turning it gently in both directions to free it up a little before cranking it out. If there's sufficient exposed stud length, use a good-quality Vise-Grip pliers on it. The stub is likely to be just threads around the outer end, meaning an OD extractor will have little to grab.

Heat is normally your friend when removing bolts or remnants that are stuck due to corrosion or maybe Loctite. Steel bolts into aluminum, especially where there's water flow, are subject to additional galvanic corrosion issues. It won't hurt to add heat (propane torch) to the stud just to dislodge a corrosion bond with some differential expansion. Do this -before- you apply penetrants like PB Blaster, so you don't risk coking that fluid in the joint. Let the bolt cool before any attempt at withdrawal of course. The bolt will grow in the aluminum hole while hotter, as there's a lot of aluminum to heat up around it.

It's possible but unlikely that the bolts were cross-threaded at initial assembly. The QC process includes automatic insertion and testing to bolt torque. The industry convention for 6mm steel bolts into aluminum is about 7 lbs/ft of torque, a number tiny enough to cause the bolts to stop part way into the block if it's not going in correctly. Honda specs 8.9 lbs/ft for these water pump bolts, FWIW, maybe because of the flanged bolt head. The tiny numbers deserves use of a torque wrench or torque-limiting driver for assembly, with a further 10-15% de-rate for the anti-seize or TFE sealing paste we all use for bolt assembly. Find one of those 1/4"-drive Harbor Freight torque wrenches for $10-15 on sale if you don't have something better already. New bolts are a convention for some of the older German toys in my garage with aluminum blocks, for sure not a bad idea for the Pilot. Resist the urge to use stainless, as it presents its own interesting issues in aluminum. Also resist the urge to add sealant to the surface between the gasket and the block, as there's a risk of it migrating into the bolt threads/holes. It's ok to add a tiny dab to hold the gasket to the water pump body for installation, but any glue to the block means you'll be scraping and risking damage to the soft aluminum gasket sealing face on the block at the next change. Not Ideal. Use that torque wrench, and tighten (if that's the word... maybe "snug") the bolts progressively, with a cross pattern similar to the way you mount a wheel on the car. That will give you just the right amount of gasket crush and even tension on the bolts. Plus a reasonable chance that they will come out the next time. For those who just tighten to the "that's not going anywhere!" torque, consider that the 7-9 lbs/ft of dry-thread torque is about the same as three loose fingers worth of turning pressure on a screwdriver handle, way way less than what one might expect. There's no bolt stretch to consider in this duty, as the block threads tend to yield well before the bolt even yawns with the tension. We need enough pressure on the gasket to prevent leakage, enough tension for friction on those flanged bolt heads to keep them from falling out. Any more is "excessive".

... In my limited experience with such things anyway.
 

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Weld a nut to it. The heat causes the bolt to swell which helps to crush/loosen any corrosion, and gives you good way to turn the broken off portion of the bolt. After you weld it, while it's still hot, see if it turns at all. If it does, go about a 1/4 turn each way, then let it cool down. Drown it in penatrating oil and slowly work it out.
 

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Discussion Starter · #9 ·
Wow, thanks for the great insights and Dr. Bob, you were reading my mind with some of the ideas I did "NOT" implement. After three hours of misery this afternoon, I got the remainder of the bolt out. It took a level of patience I generally do not possess. I considered putting two nuts on that would fit that bolt, wondering if the inside nut would lock against the outside and give some leverage....but opted not to. Yesterday I put a small spray of PB blaster in it for good measure. Today I put some heat only on the bolt to start, let it cook, then cool down. One of my mentors also mentioned the value of "vibration", using a ballpein hammer and gently tapping aluminum block around the hold, and then the bolt....I did this. Then a pair of HF Bremen vice grips were clamped on and I rocked the bolt gently back and forth, using a long mirror to see if I was getting traction, which I was. In between, I'd tap the bolt 20-30 times, then re-crank gently with grips, trying to only turn parallel and not at an angle. There is such little space to work in and I came it from the top. Also had to be careful not to mar the surface of where new water pump seals near the hole. I think I did at least 75 of these, with a couple re-heats. Then my neighbor who is skilled in this area mentioned adding some heat to just the area around the bolt, but not the bolt directly. Where that sped things up and out it came, another 15 attempts. Was panicking when I saw black threads, but realized it was just the "cooked" PB Blaster and you can see in photos the final threads are fine. So 1/2 the mission is done, I have tried walking a screw back in by hand and that appears to be problematic, so not sure what I'll do nest. The other holes have no problem. The bolt snapped off so clean, it's possible it was weak or the threads got crossed going in. Finishing the entire job will be a breeze now, but that hole may at least need a simple retap, not my forte.
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You da man! That's a good feeling when you get the remnants out successfully. You might be able to find a tap at Lowe's; I had to re-tap the license plate bolt hole on my Pilot after it snapped off and I had to drill out the remnants. Before you try re-tapping, you might try putting some grease or Vaseline on the bolt and see if you can chase the threads. Tighten it, back off, tighten, repeat, and see if it's making any progress. If it was truly cross-threaded you'll probably have to tap it. Don't forget to put some oil on the tap so it doesn't seize.
 

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Given the amount of aluminum that came out on the bolt, I'd chase the hole with a "bottoming" tap or grind a tapered tap a few threads so it re-threads near to the hole bottom. You'll need all the thread you can salvage for the bolt to snug up to torque spec.

If you are handy, you can make a chase tap from a hardened bolt; use a grinder and cutoff wheel to cut two or three slots along the bolt length to get cutting action and gulleys to clear chips.
 

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If you are handy, you can make a chase tap from a hardened bolt; use a grinder and cutoff wheel to cut two or three slots along the bolt length to get cutting action and gulleys to clear chips.
Handy tip for midnight solution when everybody is closed. But I’d get a proper sized rethreader or tap to clean up the holes to ensure no further issues.
 

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You really want a thread chaser rather than a tap in this case. A tap is designed to cut new threads by removing metal. A good chaser will work to roll distorted thread metal back into original position. It's really easy for a tap to follow the cross-thread path left by the bolt, and leave you with almost nothing for a new bolt to grab on to.

If you find that you are a little short on remaining threads in the hole, you can try a slightly longer bolt to reach deeper undamaged threads in the block. A thread insert is the next option if the threads are too far gone. Helicoil is a popular and easily-available option. There are others that I like better, but they aren't cheap enough for a DIY one-off effort.
 

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Discussion Starter · #14 ·
I don't think much aluminum came out. What looks like aluminum is just the good threads being eaten by the vice grips. The only part of the screw that was stuck is the black bottom maybe 1/4 inch worth. Though the hole was clearly "tight". I think a thread chase make sense for the next step, just have to make sure I get the right size. Was trying to locate this "scope camera" I have which attaches to my cell phone and allows me to take a photo of tight spaces. Not sure if I can get a good view or not, it was designed for plumbing situations where you can't see, but is no larger around than your pinky finger. I'll post if I find and can use my device.
 

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The bolts are 6 x 1.0 mm. Look for that size thread chaser. Sometimes Ace hardware stores have them. Else a brown truck from Jeff B. will drop one off to you.

My inspection cameras are too big to fit in a 6mm threaded hole. I guess it could look closely from outside, but realistically a good inspection mirror will let you see well enough into the hole. Clean the hole thoroughly with you favorite spray something, lubricate the chaser or tap as you use it to restore the threads. Clean again before you put a bolt in there.
 

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Discussion Starter · #16 ·
Just a quick update, I'll get more pics in time. Spent 10 hrs last Saturday getting the bolt hole cleaned out. Bought a small pack of thread chasers at Summit Auto Racing and the 6mmX1 was perfect. Took a while to get threaded back through, making sure I was putting in straight. Once I had gotten most of the way in, a fair amount of small metals pieces cam out on a few turns, then sprayed out with brake cleaner. Was able to finger a new bolt in well and not loose. Got car put back together by 10 pm, then went to fire it up. Sounded like a smooth machine and was very happy, also only had one small bolt remaining, likely a clip or something insignificant. Sunday got a car wash (with Chassis bath), gassed up and while coming home, car sputtered, all dash lights came on and car went into frozen protect mode and died. Rather disappointed, I had it towed to dealer with great regret late Sunday evening. Tow guy could not get wheels into Neutral, so car was "drug" gently across a gravel lot and up the flatbed. Did discover the handy little knock out button near shifter that allows a scredriver to manually put dead/frozen car into neutral so tires will spin. Never knew that one. Monday morning I got a video reply from our local Serra Honda dealer. I opened it slowly and discovered they quickly located where that last bolt belonged...... on the negative cable that attaches back inside the engine. Topped off the coolant overflow, and shazzam.....car is fine. OMG and WTF was all I could think, damn near cried. They said it looked like I did a good job. We'll drive for a while and report back. Thanks for everything and whatever prayers happened.
 

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