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Broken Head bolts removal

K

Klink

Regular Contributor
I removed the head on a 1990 70hp Evinrude and 6 of the 14 bolts broke off. When I removed the head, I found that luckily the remaining bolts protruded out like studs. In the past I was able to easily remove the "studs" by using PB Blaster and a center punch and mallet to break them loose, and then removing them with a vice grip. In this case, not one has budged after trying many times. It appears that the aluminum oxide corrosion on the bolt threads do not allow the PB to penetrate down the threads (I've sprayed it 3 times a day for 5 days).

Yesterday I tried heating the aluminum around one bolt with a propane gas torch, but it seemed to cool down too quick like the heat was quickly dissipated throughout the block. How hot can I get it without damaging the block?

I tried heating the bolt then spraying it with PB to see if it would suck in the PB as it cooled, but it did nothing either. I am just heating it mildly, not heating it to where it changes color. Again, how hot can I go with heating the bolt without damaging the head, red hot?

I am go to try candle wax instead of PB.

If none of this works, I will have to take it to a welding shop, which could be costly.
 
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Had a big tree fall over into my yard, engine will have to wait a few days. It's humid and like 100 degrees today, maybe that'll loosen the bolts. I'll try the wax thing tomorrow.
 
You need heat. Hot concentrated heat, like acetylene torch heat. Heat the aluminum around the side of the bolt. Yes you will scorch the paint. That's the price we pay here in FL salt water.
 
What about welding a nut to the protruding end of the head bolt then using an impact gun on it? I know that sounds extreme, but you're definitely in a pickle already.

The idea comes from a GM 6.0L truck I used to have. The engines use aluminum heads and they are notorious for breaking exhaust manifold bolts. Often the bolt snaps flush with the head and one method is to drill with left handed drill bits then use bolt extractors. This can work, but getting off-center can be a huge problem and is a pain with head still on the engine.

The other method is to use a wire welder to build up the steel bolt (won't stick to the aluminum) then that gives you something to grab onto. In your case, welding to a nut to the bolt will give it a lot of quick heat and then the nut gives your something for better leverage. I've often found that steel bolts threaded into aluminum respond best to impact rather than straight twisting force.

I can't say this will definitely solve you problem, but it's something to try.

KJ
 
Grind the end of the studs flat and center punch them. Then drill a small hole center of the bolt all the way through the bolt now stud so the pb gets inside threads. Then get a reverse spinning drill bot a little smaller than the inside threads of the bolt. Use firm pressure and once the bit gets about half way in it usually will get enough a grip to back the bolt out. The key is to get the penetrant to the inside threads my favorate is power steering fluid it dissolves corrosion and does not dry out.
 
My 14 year old son with his Harbor Freight 100 amp mig welder welded a T on one of the broken bolt studs that stick out, and he got enough grip from the weld with a vise grip, that he broke the bolt flush. If he would've asked me, I would have heated and oiled the area first and worked the stud back and forth to get it loose. At least now we know how to remove the other 5 bolts. The single broken flush bolt, I drilled progressively larger with left hand drill bits, but it never budged, but the final hole left very little bolt left and we were able to cave in the bolt sliver at the edge and get it out. I was able to get a new bolt into the hole, the threads are good.

One down, 5 to go, but we now got a plan for the 5 remaining that I think will work.
 
kimcrwbr1 said:
Grind the end of the studs flat and center punch them. Then drill a small hole center of the bolt all the way through the bolt now stud so the pb gets inside threads. Then get a reverse spinning drill bot a little smaller than the inside threads of the bolt. Use firm pressure and once the bit gets about half way in it usually will get enough a grip to back the bolt out. The key is to get the penetrant to the inside threads my favorate is power steering fluid it dissolves corrosion and does not dry out.
Click to expand...

Drilling the bolt hole through would then allow penetrant to pool up and behind the threads, as there is about 5/16" of space below the bolt threads before you hit the base of the hole. Then I could let it sit full of penetrant to the top for a week or so as I can't get to this job for days, good idea thanks. Will do that if the T weld does not work.​
 
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We finally got the last two bolts out today after days and hours of attempts, we started on July 25 and ended today October 17. We did it mostly with the welded T method described above. All the bolt studs broke off with the welded T method and then we had to work with a flush to surface bolt and build it up to a T or L and then we attempted to remove it with a Crescent wrench. We'd clean the flush bolt and weld the T and try to turn the T, but it would just break off. Welding the T turns the bolt red hot and we applied wax from a candle, a recommendation found online, that worked better than PB Blaster. We kept doing it till we finally got the bolt to break loose and got it off. We got 4 off that way, one of which we drilled a bit down the center to get a better weld grip, but it didn't make much difference. We did rough up the flush bolt heads with a center punch to get a good weld grip. Two of the 6 bolts I had to left hand drill but they did not come out, and the sliver of metal that was left, I got out with picks and a tap.

The propane torch was useless, it does not generate enough heat and the aluminum block dissipates the heat as fast as you lay it down. We generated heat by welding the bolts, then put a candle on it while red hot so it would suck it into the threads.
I think an acetylene torch would have heated the area, but it would have been near impossible to control in such a tight space. Besides, I do not have an acetylene torch. ​

In the end, the best method is to weld the T, apply candle wax when red hot, then pour water to cool, and use the Crescent wrench to turn the bolt off. It is a good idea to turn the bolt a bit clockwise if it does not move counter clockwise or gets hard. (Most importantly we did a ton of prayers to St. Joseph to help us!)
 
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What remained of the stuck bolts was flush with the surface of the engine head, that is what we had to work with. ​
Here's what a bolt looks like after we welded T or L on top of it. (P.S.- online sources recommend welding a nut on the bolt, but that did not work very well, we tried with 12 nuts on different days and it only worked once)

Pio's T weld.JPG
 
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I have done this perhaps hundreds of times too. Heat the aluminum with a carburizing flame with your acetylene welding nozzle, about a #2. If the bolt is protruding any, you tap in on it when things are hot. The key here is to heat quickly and knowing when to stop. Map gas will give you much faster heat in your small torch than propane. It is cheap too. Anyway, once you have tapped on the broken bolt, quench it with cold water. Then weld on your piece, or nut....whatever suits you. When welding on a nut, use a 3/8 nut, for instance, on a 5/16 bolt.....so one size larger. Nice part about using a nut is that it keeps the weld apart from the block, or head surface. Also use as high of a heat setting on your welder as possible. This time let it cool slower because if you quench it too fast, it will weaken the weld bond of the nut to the bolt. A solvent quench of say atf and mixed gas will actually work into the hot threads a bit.,Then fire up your torch, but don't get it quite as hot as before, when you tapped on it. Why? Sometimes the aluminum will stick to the bolt and create even more friction. So, then, while it is toasty warm....crank it out with a small box wrench or socket on a breaker bar so you can rock it if needed.
 
Glad you got your job completed. Seems you worked yourself to death. I just dealt with a broken bolt day-before-yesterday. I ground it flat, center punched & drilled it out with a counter rotating bit that was a single size under the bolt. It was a 1/4" bolt, so I used a #7 bit. Finally, I used a 1/4" 20 TPI tap to clean the remnants of the old bolt out of the hole. Installed the new bolt & didn't look back. Maybe 2 hours worth of work, including getting out tools & cleaning up.
 
We had to do 2 of the 6 stuck bolts with the left hand drill method, but the left hand didn't get the bolts out, it just drilled them. We also tried screw removers on them as we went along from small drill to larger. On one of the two we were able to drill and get every bit of the sliver that was left off, without tapping. On the other we had to tap to finish cleaning it all out. The drilling in my case was more hazardous, and I would have had to remove the entire power head to drill the 3 bottom bolts. The welding does no harm to the aluminum. Had we had Acetylene it would have been much easier, but, we were working in a tight space and I have no acetylene torch. I had to work with what I had, a 90amp welder, left hand drills, screw extractors, Propane torch.
 
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Can anyone tell me why I no longer receive notice by email of responses to my threads and postings? What do I have to check to correct that?
 
I have no idea why your notifications would have stopped. You might just reply and click on ADVANCED. Before you click submit, be sure to check the box for subscribe then checkin INSTANTLY, USING EMAIL. If your subscriptions don't start again you'll probably need to contact the site admin to ask them directly.

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Quick question on this topic. If I decide to go with the weld method to remove a broken bolt, do I need to be concerned about anything on my motor? Electrical? Any bearings? I don’t want to damage anything else if I go with the weld method.
 
daleshank said:
Quick question on this topic. If I decide to go with the weld method to remove a broken bolt, do I need to be concerned about anything on my motor? Electrical? Any bearings? I don’t want to damage anything else if I go with the weld method.
Click to expand...

Yes, you have to be concerned. The welding spark can ignite the fuel and burn your engine, it can melt wiring, plastic, and who knows what. I made sure there was not even a fume of gas in the carbs and engine, and I covered the engine with wet towels and had a fire extinguisher close at hand. The welding sparks can also ignite any fuel nearby, like a gas tank. You have to be very cautious. The most dangerous fuel is in gas form, like in an almost empty tank or almost empty bottle.
 
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Years ago , when I worked on cat motors , they were notorious for breaking exhaust ss studs
Down in the hole. I was the guy to get them out, back then I used a stick rod called extract-alloy, wouldn't weld to the cast, just stick rod in hole till it was to the surface quickly weld on a nut then , take a can of freeze spray, spray nut till it had ice on it. Put boxend wrench and screw out.
 
Pretty cool, Gator. See the guy blowing flame away with grinder fan? Tough weld because shielding gas being disturbed too. Mikey....yes use 'em too.
 
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