Extracting broken bolts from a head

I am nearly at my wit's end, so I thought I would ask here.

Have two grade 8, 3/8" coarse thread bolts broken off flush in the head of a 466 John Deere engine. Got the combine ready and drove to the field. When I got out i heard a bad knocking sound from the engine........after my initial sinking spell I recovered a bit and climbed up and looked, listened and felt more closely. It quickly became obvious that was a blown exhaust manifold gasket on #6 port. Had a similar problem a few years ago on another combine with same engine and our mechanic was able to take out just the bolts on that port and slip in a new gasket. So I was hopeful the repair would be that simple and I could run in the meantime with little ill effect.

Well when things were nice and cool the next morning I discovered a broken manifold bolt, so the quick and easy patch job was out! I ordered gaskets for both intake and exhaust manifolds, turbocharger oil ports etc as well as a set of bolts for the exhaust manifold. After removing everything I had 2 broken intake manifold bolts and another exhaust bolt. The intakes were broken off with about 3/4" sticking out of the cast iron head and were threaded all the way to the bolt head, so I screwed a nut on to the stump to weld and extract them. Lo and behold, as I was tightening the nut up, each bolt began turning in! Reversed the ratchet and they both backed right out!

That left the exhausts......
So far i have drilled all the way through the bolts with about a 3/16" bit. I am centered up quite well, but may have a slight angle away from the axis of the bolt on one of them.

Then I sprayed with PP blaster on one of them and ZEP on the other. I have had good luck with ZEP in the past, but have heard that blaster was really good too. So both have been soaking with penetrating oil in between all the other attempts for a day now.

Tried a spiral easy out. It was a little small, but no luck...decided to heat the bolts to expand them, spray again/ let them cool completely and tried again with the easy out.......no luck........but I didn't want to snap the easy out off, so I didn't go for broke.

Easy out was a little small, so I got next size bigger spiral style and tried that.......no luck

Heated the cast iron around each one....didn't manage to get it red hot or anything......tried easy out again...managed to snap the square shank off it this time. Luckily it didn't snap flush with the bolt surface...... but bolts didn't budge

Decided to drill to 5/16 with left cutting drill bit in the hope it would catch and turn the stumps out......this works amazingly well, being successful more than half the time in my hands........well, remember when I said I heated the bolts to expand them and then cooled them.........that sounded like a good idea to me, but it hardened the bolts so I cannot drill them at all! Big mistake......

Next idea was to cool the bolts to shrink them in the warm cast iron. R134a is not exactly cheap but I am desperate (though not desperate enough to spray them with liquid propane which I also have and is a lot cheaper than the 134a). I have a drum of refrigerant sitting by, so I rig up a tiny tube and fitting to spray liquid refrigerant into the holes.....no.......cannot really freeze the shell of the bolts, the heat transfers in from the head too well....nothing moves with the easy out (which i have ground a new square on).

By this time, the local mosquitoes have punched into work as the sun goes down and I am getting eaten up, so I sprayed them good again and quit.

Any words of wisdom? I am considering trying some sort of carbide bit to drill them to 5/16, perhaps with a magnetic base drill if i can rent one that's not too big to work through the access panel in the rear wall of the grain hopper that allows you to actually see this site on the engine that is mounted about a foot away on the outside.

I already screwed up big time heating them with the torch, don't want to do anything else stupid

All ideas welcome !

When desperate I have warmed up the housing (head) and used Dry Ice to cool the bolt/stud and then applied force.

I also like the left handed drill bit for soft bolts

The only "easy out" extractors I've had any luck with are the ones made by "Ridgid". These are a straight spline type that doesn't expand the broken bolt in the process. Comes in both broken pipe and bolt sizes. I believe I got them from McMaster.

This is the type
http://www.mcmaster.com/#screw-extractors/=zcbrgd

Forget the penetrant, heat them up again and stick a candle to them. It will suck the wax into the threads and make them come out easily.

I've made that mistake of hardening the bolts by heating them too. Then the EZ out won't bite. Time to get out the torch and a fine cutting tip and blow them out without messing up the threads.

https://www.ridgid.com/us/en/screw-extractors

I had 4, 1/2 bolts that were broken as you describe. I drilled clear through (mine were blind as well). I was centered really well and not into the threads. I took my mig welder with .030 wire and carefully filled up the hole with weld, not lots of heat but it doesn't take a lot. Once I filled the hole I slowly built the end of the bolt up until I could weld a nut on it. Then let it cool completely, once cooled I used a air hammer set on low to vibrate the snot out of the nut/bolt, then I put a wrench on the nut and vibrate whilst applying torque both ways. Pretty soon you'll get it to wiggle then bring it on out. You might break a nut off a time or two but you'll get it.
The reason for welding the hole clear up is it seems the internal weld heats the bolt up real good to break the rust bond.
It might be tricky with 3/8 bolt but I'll bet it can be done. Good luck

Bruce

Bruce I reckon your on to it or at least thats the way I would be trying to get them out if that still dosnt work pull the head and get it into a drill press

Ive never had much luck with easy outs I tend to skip them now drill a hole in and blow it out with the gas axe if its a big bolt and just clean the thread with as tap when done


Paul

I have some small die grinder burs from Enco. They are 1/4 inch round and have been able to grind out bolts to the threads and with a seal pick remove the threads.

I second this technique for blind holes. Use a tungsten carbide burr and slowly open the hole until you can see the helix of the minor diameter. The rest can be picked out with a scribe. If you use a tap to get the rest cleaned out, use a bottom tap because it will be less likely to ride over and and create an adjacent double thread.

Is it possible to reinstall the manifold and use the thickness of the flange as a guide bushing for your drilling attempts? If there is to much slop in the holes on the exhaust manifold it probably won't work too well, but I have had good luck using a "guide bushing" such as this. 5/16 is the tap drill size so it needs to be spot on. If you can manage that you can pick the rest of the bolt out like a slinky.

You would need to make a bushing whose od was interference fit in the manifold and id was 5/16 to get you centered.

when i do them at the the shop for work.1 would drill / grind out to your tap drill size then use a bottom tap to push the remainder to the bottom and use a good o ring pic to work at it. drat tips work grate for small punches. what i would do if you can get a welder in there mig works good is weld your nice hole shut that you just drilled and well a nut on the top good and hot. when it cools it will have shrunk just like doing bearing races. if it's not loose by then just drill it out and re-tap. throw them" easy out" back in the JUNK DRAWER and leave them there. try not to use a taper tap when re taping the holes as it's easier to get thing messed up and it will pinch and wedge any parts of bolt rather then pushing them out. you will also need a cup of coffee i try and do my in the mornings before my patients run out for that day lol. good luck

Hi, CCJersey.
Many people seem to have their own pet methods for stud extraction. Mine is to take a spring or flat washer for the next smaller bolt size and weld it to the broken stud. Then take a nut of the bolt size or next size up and weld it to the washer. Then walk away and have a coffee or three - or a beer, or rum, or bourbon, or a snooze - while the whole issue cools out.

When all is down to ambient temp. or close to it, use a hammer and punch to give the welded on nut a few good raps before trying to remove the stud by turning the nut.

I have had a few where I have had to weld 2 or even 3 different nuts on when the weld has broken but only one has ever beaten me since 1970 when I first started using this method. In one case, I had 3 x 1" bolts broken off up to 3/4" down the hole, I slid 5/8 'sproing' washers into the hole, which was horizontal, one at a time, welding the first one to the broken bolt and each successive one to the one before it until I had a stem of welded washers protruding from the hole. I then welded a 1" nut to that stem, let the whole issue cool and screwed the broken bolts straight out.

Hope this helps.