Head bolts Stuck!

[brielly]

I'm attempting to replace the head gaskets on a 96 yamaha 250. I have 2 head bolts that don't want to come out. I assume if I break them off in the block I'm looking at pulling the powerhead and having it drilled out by a machine shop. Most likely I'll run into more broken bolts trying to do that. So whats the best meathod for removal? I was thinkning of heating the bolts with a propane torch and trying again. Would an air impact wrench be good or would that break the bolts? I'm pretty sure penetrating oil will not make it into the block to help loosesn the bolt. I was also thinking about breaking the heads off the bolts off so I could at least get the cylinder head off and have a chance at getting the penetrating oil into the area where its seized. I could use channel locks or even weld a nut to the remaining stud at that point and have at it again. Any thoughts or suggestions would be greatly appreciated.

 

[sutor623]

Re: Head bolts Stuck!

Heat the bolt up with a torch. After letting it cool just a bit put some (non aerosol if you can) penetrant around the bolt. When the bolt contracts because of the cooling it will draw in the penetrant. Of course this will be more difficult with the head still on. An impact gun typically will be a good thing. Just start with low PSI and slowly work upwards. You could also take it to a machine shop now and maybe save time and $ in the longrun. Good luck.

 

[robert graham]

Re: Head bolts Stuck!

The heat and air impact wrench at low setting sounds like a good plan....keep working on them and they may loosen up...if it'll move just a bit, you can get it out! Good Luck!

 

[brielly]

Re: Head bolts Stuck!

I hit it with the mapp gas today...Good news/bad news. The top bolt came out and I thought the next one was loosening but unfortuately it broke flush with the block. I guess its time to bust out the left handed drill bits and hope for the best. If it doesn't work itself out I'll robably have to try a helicoil.

 

[sutor623]

Re: Head bolts Stuck!

Yea man what I have done is get a whole set of left handed bits. start real small and drill the center of the bolt, and keep getting larger. Either the bolt will come out or you will just keep drilling until you tap for a helicoil. : ) Good luck

 

[robert graham]

Re: Head bolts Stuck!

I've heard of folks welding a steel hex nut onto a bolt that's broke off flush like yours, then get a wrench on that nut....might be an option for you, save all that drilling and tapping. Just an idea...Good Luck!

 

[sutor623]

Re: Head bolts Stuck!

I've heard of folks welding a steel hex nut onto a bolt that's broke off flush like yours, then get a wrench on that nut....might be an option for you, save all that drilling and tapping. Just an idea...Good Luck!

Yeah I have heard of this too. It seems to me though if the bolt is flush with the surface, you may end up harming the mating surface if you try and weld it. Sucks if you have to pull the powerhead to get it to the drill press though. I have pyhsically seen people take a large piece of flat steel, drill out the holes for the head pattern, and start with a small hole in the steel right above the snapped bolt. Then you tighten down the steel, and have a template to keep the drill nice and straight when drilling the studs out. Gradually get bigger and bigger until you can tap for a coil. Works like a charm if the drill press is too hard to get to.

 

[robert graham]

Re: Head bolts Stuck!

Maybe the drilling, retapping/helicoil is the best way to do this?...what a headache!:facepalm:

 

[sutor623]

Re: Head bolts Stuck!

Maybe the drilling, retapping/helicoil is the best way to do this?...what a headache!:facepalm:

I know, right! But it is what it is. I had a welder one day, drill the bolt out on my 9.5 evinrude, fill it with molten aluminum, and then re-tap a new hole. Only charged me $40 (a half shop hour) and I even got to watch him do it. So it doesnt have to cost an arm and a leg to have this type of thing handled by a professional. : )

 

[robert graham]

Re: Head bolts Stuck!

Wonder if a talented welder could weld a stud onto the broken bolt, then use a nut to tighten the head down?....that could work!...just another idea!

 

[sutor623]

Re: Head bolts Stuck!

Wonder if a talented welder could weld a stud onto the broken bolt, then use a nut to tighten the head down?....that could work!...just another idea!

Only problem there is that I doubt that youd be able to torque the head down to spec. Plus all of the mechanical vibrations of the motor would eventually cause for that weld to break. That bolt needs to come out!!!

 

[robert graham]

Re: Head bolts Stuck!

Well, back to the drills, taps, etc..... Would as Easy-Out work?...drill a little hole in the broken bolt, then an Easy-Out on an impact driver....That could work!...

 

[brielly]

Re: Head bolts Stuck!

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When I got back to the boat today i realized I was looking at the wrong area. The bolt was actually broken half an inch inside the block but luckily it was a clean, flat break. I center punched it and started with the left hand bits. I also drilled a small hole into the block at a 90 degree angle to the threads to get more penetrating fluid in there. The drilling wasn't go very strait and i almost gave up. Too much more off center and I would have drilled into the water jacket and it would have been game over. I straightened the hole with my dremel and went to the largest size bit. A few seconds and that sucker came right out. I did mess up some of the threads so I'll get some epoxy thread repair just to be safe. You gotta love the left hand drill bit! Thanks to everyone for their help. Hopefully there will be no more surprises on this project.

 

[villtur]

Re: Head bolts Stuck!

When dealing with cases like this the best method, by far, is getting mig welder and weld on top of existing bolt. Add clots of iron until possible either to grab the weld with vise grip or weld a nut onto the clot. Do this slowly and in very short bursts as not to melt the aluminium. If done properly it won't harm head (much). Let cool down completely. The bolt should come out with little persuasion.

This is the method engineers here in Iceland use to deal with broken bolts in car engine heads, e.g. when dealing with exhaust manifolds, and I can confirm it also works for outboards. But congrats on your result with left hand drills.