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Discussion Starter · #1 ·
sucks when a simple job takes a turn for the worse.. removed thermostat housing, one of the bolts broke in the block. simple solution was (i thought) drill hole in bolt and use EZ-out. well the EZ out broke inside the bolt as well. got a carbide drill bit and have started drilling the bolt out entirely. planning to tap a new thread one size up. just thought i'd ask if there was a better course of action before i finished the job. any advice is appreciated. thanks guys.
 

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Heli-coil.
 

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Discussion Starter · #3 ·
Amen to that sign lol.
Never used helicoil before. Is there an advantage over tapping?
 

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drill and tap
 

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Had this happen on a Ford 5.0 block as upper was Cobra aluminum intake and Ford used steel bolts lol. Went to do tstat housing and two bolts sheared off. Took a shop hours and heat to carefully extract as in the Explorers/Mountaineers it's in an very awkward spot to get to in engine bay and two bolts were beyond seized. Had to be super slow and careful as upper aluminum manifold you were fubar on that block if you screwed up even retapping threads. A $10 t-stat turned into a $$$ job lol.

Still have that truck, 331 stroker kit haha
 

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Depends. If you drill it out you might be able to save the factory threads and knock the current bolt out.

Helicoil so you do not need to go to a bigger bolt thread size that might not fit the thermostat housing holes. You can keep the same both tap size or go smaller if you don't have enough material on the block for the new tap. You still need to tap the with helicoil.

They are other thread inserts like helicoil too.
 

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Buy a new engine
 

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Discussion Starter · #8 ·
Thanks guys. The thermostat gasket had given up at that exact bolt location which i guess is why the other bolts came out easy but this one snapped. i think it has been leaking for a while. i noticed puddles of coolant on top of the block (looking down thru the gaps in intake) which is why i decided to replace the gasket in the first place.

I managed to drill into the easy out using the carbide bit. the hole is mostly centered so i'm hoping the factory threads. will report back with an update when i get to it... probably this afternoon when i get off work.
 

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Since it is centered, you can buy reverse drill bits. Northern tools sells them for sure as I have seen them when I was buying extractors. work your way up in sizes and hit the bolt a couple of times after each drilling.

You might be able to use regular bits and take your chances drilling as you go up in size. Whacking it will help a lot. and yes I mean that in both ways:D
 

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Discussion Starter · #10 ·
LMAO thanks Rob... i did and it helped! XD
barely any bolt left. tried heating the area with MAP torch and using another extractor but felt like extractor was going to snap off again. used a cobalt reverse drill bit and it snapped too. only thing that has been working is tungsten carbide cutter.
looking into helicoil i read that the hole needs to be deeper than how far the helicoil and bolt actually go (in order to break off bottom tang). is there enough clearance in that area of the block to do that? other option would be to tap one size bigger and also open up the bolt hole in the housing to accommodate. not sure which route would be safer?
 

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Look into the different types of threaded inserts or threaded bushing. then decide on what is best.

Can't help you with how much material there is for drilling in that hole.
 

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sucks when a simple job takes a turn for the worse.. removed thermostat housing, one of the bolts broke in the block. simple solution was (i thought) drill hole in bolt and use EZ-out. well the EZ out broke inside the bolt as well. got a carbide drill bit and have started drilling the bolt out entirely. planning to tap a new thread one size up. just thought i'd ask if there was a better course of action before i finished the job. any advice is appreciated. thanks guys.
I had that happen while replacing a water pump on a neighbors car. There was a small stub sticking out, so I clamped a vice grip on the stub, heated the block area around the stub to expand the metal a touch, then used the vice grip to unscrew the stub. Whew. That's what I get for trying to be a good neighbor and save them some money fixing their old crappy run down car.
 

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Four years as a machinist in the Air Force. I've removed literally thousands of stripped and sheared screws. If you've managed to get the EZ-out removed I'd drill out the rest of the screw up to the inner diameter of the threads. Dump a bunch of penetrating fluid on it (not WD-40 that shit is no good for this), real penetrating fluid. Then I'd take a chisel and hammer and cave in the sides of the screw. After removing the bits of the screw I'd run a tap in the hole to clean the threads. That's what I would do, but I'm a professional.
 

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I'm a machinist by trade and I can tell you there are some solid recommendations in this thread, and some not so solid ones. That said I'll add a few of my own since I do shit like this for a living. First and foremost you need to figure out the thread size. I have a Gen II engine in my basement so I checked the thread size for the thermostat housing and its 1/4-20. With that information you can determine what size drill is used to create the minor diameter of this particular thread, in this case a .201 diameter drill is used for a 1/4-20 thread. Since the broken extractor is out of the way now, use a drill that is slightly smaller than .201 (lets say .1875) to create a pilot hole. I have no idea what size hole you drilled to use the extractor, but hopefully it was smaller than .201. It is CRITICAL that the hole be ON CENTER. If the hole isn't on center you've opened up another can of worms that I won't cover in this post. After this hole that is ON CENTER as been created you may be able to pick out the remnants of the old bolt. If that isn't possible, then you gradually step up the size of the drill until you've reached the maximum drill size of .201. If you make the minor diameter any bigger than .201 you're going to start compromising thread strength. A 1/4-20 tap can then be used to chase out the remnants of the old bolt if you are unable to pick them out.

I don't like to use heli-coils unless I have too. They are a good option when someone has boogered up a hole beyond repair, but normally aren't needed if a broken fastener is extracted properly.

On a side note broken bolt extractors will often times cause more problems than they solve, especially the long, small diameter ones. If you are using one and it doesn't pull the broken bolt out with minimal force then STOP, back it out, and go to the method I detailed above.
 

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If your threads are damaged enough not to be able to hold a bolt securely, but not completely lost to the bottom, then you should invest in a Time-Sert set for 1/4"-20 thread. These kits contain a special tap that uses the existing remnants and oversizes them slightly. Then, you do a slight countersink at the top of the hole. Finally, you place an insert from the kit onto a drive arbor and screw it into the oversized new hole. The insert itself has outer threads that are machined 'in time' with the original threads, with internal threads 'in time' with the outer threads. This yields a minimum diameter thread insert that can safely be used in aluminum, steel or cast iron hole repairs. We have multiple sets for common, and some uncommon threads encountered in my heavy construction company and my shop superintendent just loves them.
 
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Discussion Starter · #17 ·
a lot of helpful info, thanks guys. So i was able to get most of the easyout, but realized that some of it is still stuck at the very bottom. i was able to re-tap 1/4-20 threads into the top portion. the threads aren't perfect but they hold the factory torque of 95 in-lbs. since it's not as deep as before i was thinking of using a shorter bolt because trying to drill the rest of it out makes me nervous.
 

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a lot of helpful info, thanks guys. So i was able to get most of the easyout, but realized that some of it is still stuck at the very bottom. i was able to re-tap 1/4-20 threads into the top portion. the threads aren't perfect but they hold the factory torque of 95 in-lbs. since it's not as deep as before i was thinking of using a shorter bolt because trying to drill the rest of it out makes me nervous.
How many turns can you get on the bolt before it bottoms out on the broken extractor? We need to determine if you have enough thread engagement.
 

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Discussion Starter · #19 ·
8 full turns vs 11 full turns on another one. the other issue on the re-tapped hole is the threads are not consistently deep all the way around but the bolt can still be torqued to 95in lbs.
 

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8 full turns vs 11 full turns on another one. the other issue on the re-tapped hole is the threads are not consistently deep all the way around but the bolt can still be torqued to 95in lbs.

Well the good news is the math says you have approximately .400 of thread engagement with 8 full turns, which should be enough. The bad news is that it doesn't sound like the hole you drilled is on center, or the tap wasn't started straight and on center. At this point, with a fastener that only requires 95 in lbs., you'd probably be better off just shortening the bolt a tad so it doesn't touch the broken extractor and let that be the end of it. If you shorten the bolt be sure and chamfer the lead thread to decrease the chance of cross threading and destroying the threads all over again. If for some reason this fix doesn't hold you have other options but for now I'd just wait and see. Good luck.
 
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