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Broken 6 mm Bolt in Engine Casing

I know that this forum is generally dedicated to our air-cooled cars. You engine builders have far more experience extracting broken things from our old 911 motors so I thought I would challenge you with my dilemma.
My issue not related to my í78 hot rod but rather to my water-cooled í06 C2S. I am replacing the water pump and one of the 6 mm bolts sheared off inside the engine casing. I attempted to use a bolt/screw extractor and the tip broke inside the broken bolt. Agh!





I have been soaking with PB Blaster, shocking and heating the ear lobe with no success.
The broken extractor tip is obviously very jagged so any attempt to drill into it is futile leading to the carbide drill to slip off and damaging the casing/thread. I have used all my Dremel bits and pieces to flatten the ragged edges with very limited success. I am now waiting for some diamond spur bits for my Dremel which should arrive in the next day or two and hope that I will be able to remove the balance of the extractor tip with them.
Working space is a problem. Things would be easier with the exhaust headers and muffler removed but Iím hesitant to do so fearing more broken bolts. The thread on the ear does go right through but there is limited access from the back side as the exhaust header is in the way.
If and when I get this broken bolt out, there is room behind the ear to put on a nut with an extra long 6 mm bolt if I somehow damage the threads.
Any thoughts on how to extract the broken bolt would be appreciated.
TIA
Johan

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Old 02-13-2020, 07:34 AM
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You're screwed... might try left hand counterclockwise cobalt drill bits after you can get a bite.
Old 02-13-2020, 08:53 AM
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While i am not a fan of many water cooled Porsches i have worked on 100's and 100's over the years from 924's to 991's and everything in between. I wont even try to remember how many 944 water pumps i have done.

I have probably replaced 100 + water pumps on 986,987,996 and 997 cars.
very rare to see the bolt break like that but i have had a couple due to corrosion on the threads.

Not sure what to suggest you do about the broken screw extractor but if you can get that out drill the broken bolt out and TIME SERT it and you will be good to go.

If you screw the hole up and it gets too large TIME SERT it with a 8mm insert and then you can buy a 8mm to 6mm step stud from Belmetric or someone like that.

Richard
Old 02-13-2020, 09:48 AM
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You should be able to use a small carbide ball end on the dremel to effectively center drill down through. Go all the way down and this will take a long time. Once you have a deep opening all the way down you need to redrill using incremental sizes until you get to the outer threads. It will likely not be centered so be careful. Then lots of heat and the extractor should work.

That is a process I have used successfully for flush broken head studs on 911 cases.
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Old 02-13-2020, 10:23 AM
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When heating do not heat the broken stud, just heating around the stud and the block.
Old 02-13-2020, 02:47 PM
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Many thanks Richard and Jamie for your valued suggestions. Staying on centre as much as possible in the real key. I have resigned myself to accepting that this is going to be a long tedious process where patience and luck will likely be the winner. I’ve heard lots about time serts over the years but luckily for me I have not had to deal with them yet.
Nice to know that there is an alternative solution if all hell goes.....
I’ll keep you posted.
Cheers,
Johan
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Old 02-13-2020, 03:18 PM
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I'd be tempted to weld a nut on the stud.
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Old 02-13-2020, 05:17 PM
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Quote:
Originally Posted by Trackrash View Post
I'd be tempted to weld a nut on the stud.
I know very little about welding but have read about the nut weld solution.
In my situation, the diameter of the initial hole is about 9 mm which reduces down to 6 mm diameter at the threaded portion. The step down and coincidentally the broken bolt is about 3 mm from the face. Can a good welder get into a nut of say 4 mm thread to weld on to the 6 mm broken bolt?
Johan
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Old 02-13-2020, 06:44 PM
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Use Jaime's tip of using a carbide ball cutter and a die grinder or dremel tool. Try to bring the hole back to center before drilling it out with a 5.2mm or 13/64" drill bit.
Another thing you could try is a small chisel and tap the screw extractor clockwise to see if it will loosen up.
I'd probably make a guide with a drill press out of steel bar stock, then bolt or clamp it up to the block. Drill one hole and drill and tap another. That would at least ensure that your new hole and threads are square to the old one.
Old 02-13-2020, 09:05 PM
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Quote:
Originally Posted by Uwon View Post
I know very little about welding but have read about the nut weld solution.
In my situation, the diameter of the initial hole is about 9 mm which reduces down to 6 mm diameter at the threaded portion. The step down and coincidentally the broken bolt is about 3 mm from the face. Can a good welder get into a nut of say 4 mm thread to weld on to the 6 mm broken bolt?
Johan
You would get in there with a mig and tack, very hot, to build a peg as large as possible, the weld won't stick to the aluminum. Then weld a larger nut, like an M8 to that peg.

Never use that kind of extractor, they break more often than they extract...
If you have to drill the stud/screw as large as possible, its better to risk damaging the threads because it might not matter much and if it do a heli coil is easier to do than a broken extractor...
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Old 02-14-2020, 06:49 AM
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Quote:
Originally Posted by safe View Post
You would get in there with a mig and tack, very hot, to build a peg as large as possible, the weld won't stick to the aluminum. Then weld a larger nut, like an M8 to that peg.

Never use that kind of extractor, they break more often than they extract...
If you have to drill the stud/screw as large as possible, its better to risk damaging the threads because it might not matter much and if it do a heli coil is easier to do than a broken extractor...
That would be my plan. Or drill out a 6mm nut slightly to get better access with the mig wire.

The real question is access to the area with a mig torch. If the motor is out, or you can get the torch in there, I would give it a try.
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Old 02-14-2020, 07:37 AM
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I second on what safe said, stay away from that type of extractors. They are very hard/brittle and therefore prone to breaking. Then you have a much bigger problem as they resist drilling completely. Re drilling method, once you have drilled through, heat the surrounding area and go easy. As others have mentioned, I think you can get a MIG tip in there and build on the stud. Side benefit it will heat the area and should aid in removal. Good luck!
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Last edited by brighton911; 02-14-2020 at 04:57 PM..
Old 02-14-2020, 04:51 PM
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A tool that really helps with your space issue is a small sized, right angle, drill chuck extension. I recently needed to center drill an exhaust manifold stud that was broken flush (on a 4 cylinder Infiniti/Nissan engine) - no space whatsoever for even my smallest pencil die grinder, so I used the right angle extension chucked into a standard size die grinder. I first attempted it with a cobalt drill bit, but started to get that bisch so off center that I switched to a carbide burr ( like Jamie mentioned above) and got it done. By the way, I used a spiral extractor and fortunately it didn't break (I was shiiting myself the whole time turning it, however ).
Old 02-14-2020, 10:01 PM
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I used a Dremel diamond wheel to boar out a broken easy out from a lawnmower engine. It still took awhile.

7144 Diamond Wheel Point
Old 02-14-2020, 11:52 PM
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I used a Dremel diamond wheel to boar out a broken easy out from a lawnmower engine. It still took awhile.

7144 Diamond Wheel Point
THANK YOU!!!! I just got some diamond wheel points from Amazon but they are too small and wear out in no time. Will run up to Home Depot who now have the one you used in stock. As you pointed out, it will take awhile and Iím prepared for that.
Cheers,
Johan
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Old 02-16-2020, 03:38 AM
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Good luck to you on this, Sometimes you can use a sharp center punch to dislodge the ez out
This is the reason that I threw out all extractors many years ago and don't let any of the mechanics who work for me use them
Throw them away !!
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Old 02-16-2020, 09:33 AM
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I know you don't want to be defeated by a broken bolt but Stop wasting time and money go find a machine shop with an EDM machine they can burn it out for $50.
Old 02-17-2020, 04:23 AM
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SUCCESS!
Two Dremel diamond points did the trick. Special thanks to HaroldMHedge for suggesting.
Cheers,
Johan
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Old 02-19-2020, 12:05 PM
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Johan,

You're welcome and I'm glad you successfully removed the bolt.

Harold

Old 02-20-2020, 12:57 AM
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