Block crack???

[Bob22222]

I wouldn't recommend welding, first you are dealing with an aluminum head and you're not an experienced welder, major damage can be done to the head trying to weld in this situation even if done by a profession welder.

I'm thinking since you stated you have tried heating the stud, etc., you are going to be forced to in the end having to very carefully drill out the broken bolt and re-tapping the threads, I understand that the space is limited, but you may have to remove other components to make more room to do so, a right angle drill may be the tool of the day to achieve this, but you need to be carful to try and drill as straight as possible and centered into the broken bolt.

Not an easy task to be sure but may be the only way to fix your issue.

It's going to be really tough to drill that one especially with the right bits and a bit of experience. Thats why I suggest carefully trying to brake the bond most likely caused by some type of reaction between the different alloys over the years. Rather than torque That's why I'd try and work something like "marvel mystery oil" (I think they call it. I believe it's something like a mixture of ATF and Naptha or Acetone . Anyone who knows please correct me here.) but the stuff comes in a red and black can and is pretty good at penetrating corrosion. (Careful. It's also good at destroying paint finish.)
....but I'd expect a 50/50 chance the softer (female) threads will be in pretty rough shape from the above mentioned corrosion. But they since don't have to bare a lot of torque they won't have to be in the greatest shape.
Maybe the OP will let us know where he's at.

 

[catrains]

MMO / marvel mystery oil is not a solvent . this is a oil conditioner that breaks down the oil deposits and sludge/carbon.

NO acetone in MMO . also does not do any damage to seals/plastics/fuel delivery system .

this product is also used in Diesels as a cleaner in the engine oil and fuel system.. been around about 100 years ..

it can be used to loosen RUST if its soaking as it does penetrate over time.

I use this product for over 30 years . never damaged any paint because its NOT a solvent.

 

[AuSeeker]

It's going to be really tough to drill that one especially with the right bits and a bit of experience. Thats why I suggest carefully trying to brake the bond most likely caused by some type of reaction between the different alloys over the years. Rather than torque That's why I'd try and work something like "marvel mystery oil" (I think they call it. I believe it's something like a mixture of ATF and Naptha or Acetone . Anyone who knows please correct me here.) but the stuff comes in a red and black can and is pretty good at penetrating corrosion. (Careful. It's also good at destroying paint finish.)
....but I'd expect a 50/50 chance the softer (female) threads will be in pretty rough shape from the above mentioned corrosion. But they since don't have to bare a lot of torque they won't have to be in the greatest shape.
Maybe the OP will let us know where he's at.

I wouldn't do the drilling unless it was a last resort.

Marvel Mystery Oil is good stuff, I have use it many times over the years to free up engines that were locked up from sitting for many years, but not sure it would be any better than any other good penetrating oil/lubricates, the ingredients in Marvel Mystery Oil for those interested are as follows.

https://en.wikipedia.org/wiki/Marvel_Mystery_Oil

"According to the company's 2015 safety data sheet:
Petroleum Distillates (Hydrotreated Heavy Naphthenic) also known as mineral oil 60-100%
Petroleum Distillates (Stoddard Solvent) also known as white spirit 10-30%
Tricresyl phosphate 0.1-1.0%
Ortho Dichlorobenzene 0.1-1.0%
Para Dichlorobenzene <0.1%"

 

[Bob22222]

I wouldn't do the drilling unless it was a last resort.

Marvel Mystery Oil is good stuff, I have use it many times over the years to free up engines that were locked up from sitting for many years, but not sure it would be any better than any other good penetrating oil/lubricates, the ingredients in Marvel Mystery Oil for those interested are as follows.

https://en.wikipedia.org/wiki/Marvel_Mystery_Oil

"According to the company's 2015 safety data sheet:
Petroleum Distillates (Hydrotreated Heavy Naphthenic) also known as mineral oil 60-100%
Petroleum Distillates (Stoddard Solvent) also known as white spirit 10-30%
Tricresyl phosphate 0.1-1.0%
Ortho Dichlorobenzene 0.1-1.0%
Para Dichlorobenzene <0.1%"

Thanks for correction. I agree cutting the stud flush and trying to drill is always a last resort for me. From my viewpoint and experience he needs to one way or another he needs to break the bond beteen the two metals while he's still got some stud left. A quick aside here, "Vice Grips" should be classified as a "dangerous weapon" when incorrectly employed on innocent machine parts. Memories of such carnage go back nearly six decades for me.
While heat might help the penetrating oils capsular movement work down into the threads. Vibration helps as help you've got to be real careful using any torch on aluminum alloys. Both torches and heat guns are dangerous around all that oil. Also, again far as I know you'll never remove a steel stud from an aluminum mass by trying to expand the steel.
I use the example mentioned in the above post (I used ATF with a touch of a acetone here) because it worked for me on one of the worst cases I had. Which involved a McCullough Super 250 chainsaw made out of crappy early 60's mag/aluminum alloy that had been seemingly sitting in weathered mire (beside the barn) for at least 20 years.
There are other very ugly and unconventional ways of dealin with that which would might involve a bit of high quality epoxy filler and a plastic stud (as a temporary mold) at the end to fill what had to be removed to get penetration down to the threads. I never recommend them to anyone but I'd sure as hell use them on my own (and my own is key here) vehicle or piece of equipment before I did something crazy like in this case pulling the head. That's as far as I'll go with that if you can't figure it you don't need too.
Learning how to deal with these things is important before you touch a wrench to a bolt. Man a tow-in on a broken bolt can be merciless in the wrong shop and a very pricey lesson even the best of shops.