I'm trying to start a thread based around bolt removal. I currently have a bolt that broke off while I was trying to re-secure the Rocker Arm Assembly. See the diagram for which bolt I broke (marked with red). It's down in the threading and the top half of the bolt broke off so I have no way of nicely getting to the bolt. I know how to use the old center punch, drill and bolt retriever method but because it's too far down the shaft I don't want to risk fudging anything up. Mechanic quoted it at $274.56 but I don't want to pay that much for a single bolt to be removed. What should I do? And are there less risky and less expensive ways?

 

There aren't a whole lot of other options really. The only other thing I can think of you can try is get some reverse spiral drill bits, sometimes they'll catch and spin the bolt right out, you're still going to have to drill anyway you slice it.

If it's a D-series head chances are you can find a good used one for less money than it's going to cost to fix the one you have.

 

I hand rotated it before putting a socket and torque wrench to it. It broke off before I could get the torque wrench to click so I'm hoping it threaded properly so it comes out easier and so I won't have to redo the threading.

 

Try inserting a thin tube, the biggest diameter that will go in. This way you avoid damaging the thread during drilling. Just keep the drill straight down so you dont damage the threads on the lower part. If you do damage the thread, you can make a re-drill and re-tap to the next bigger size.

 

Try this using left-handed drill bits:

1) dimple the bolt body
2) run in a pilot hole approx 0.5mm using 3/32" bit
3) step-up to larger size, say 3/16" and run it for 2-3mm
4) step-up to 1/4" and run it for 2-3mm
5) step-up to bit size just equiv (or slightly less than) to
inside the threads of the bolt (I think its the minor diameter of
the bolt??)

Adjust the relative bit sizes based on the size of the bolt, eg,
M8, M10 etc. Use cutting oil and hit the bolt body w/ PB Blaster
before you begin.

If the reverse nature of the drill bits has not caused the bolt body to
back out, rinse and repeat the process (steps 4 & 5) to the bottom of
the bolt body. If you are patient, you can then pick out the shell
of threads left behind.

 

See the following for illustration of minor and major diameters:

http://www.google.com/imgres?imgurl=...ed=0CDEQ9QEwBg

 

You could always take a small diameter nut and mig weld the inside (hole of nut) to the broken off bolt shaft, and then wrench out?

 

^^That would risk heating up the head too much if the bolt shaft is close to the actual head itself.

I had this problem when a head bolt rounded off on my 2zz corolla. We had to get a diamond-tipped dremel bit (or maybe it was tungsten-carbide) and eat away at the head of the bolt. Then just take the rest off normally and hope there's some left of the shaft for you to turn out by hand once you get the rocker assembly off the head.

Otherwise, the other big option would be to get a EZ-out and drill into the shaft of the bolt and use the ez-out to bite into the meat of the bolt shaft and turn it out that way. The best thing to do would be to drill into the bolt shaft, heat it up with a torch of some kind, stick the ez-out in it, hit the top of it with a hammer, grab the butt of the ez-out with a crescent wrench, get that bitch to bite and pull like hell. A cheater bar the size of yourself helps, depending on the amount of torque you put on it.