Working on my Landcruiser. The bolt in question is entitled Lock bolt in the post linked below.

http://forum.ih8mud.com/80-series-tech/185209-changing-your-belts-25-minutes-3.html#post4244791

It's the bolt that locks the adjustment bolt in place on the alternator. It's a 12mm external hex head with a star inner head. The external head rounded (or was rounded already) when I tried to loosen it to replace the v belts today. Alternator won't move if this bolt is tight. I got a star bit inside it but I'm afraid the star is about to strip too. I've got a fair amount of torque on a 18" breaker bar and it's not budging. Problem is complicated by the fact that while the picture above is with the radiator removed, my radiator is in place and there have to be enough extensions to get the breaker bar beyond the belts. This causes whatever socket I am using to twist off line pretty easily. I think that's probably how it rounded to begin with.
I bought a set of extractor sockets from Craftsman and using one of those is the next step. The bolt threads about 3/4" into the alternator itself and I'm guessing the dissimilar metals of the bolt and the alternator housing has caused it to seize up.

One option is to remove the whole adjustment bracket from the block, disconnect the alternator and remove the alternator with the adjustment mechanism attached. This may not be feasible since there is very little room to remove the alternator to begin with. I haven't yet figured out what space the alternator itself would fit through to get between the fender/chassis and the engine.

All solutions considered.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Would it be advisable to treat the bolt with some type of penetrant and let it sit for awhile? It sounds as if you are applying a lot more torque than would normally be required for a bolt that size.

I did inject some PB Blaster from the back but with 3/4" of threads my confidence in its ability to soak into all of them is very low.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

8" pipe wrench, after you cut the belt it should fit right in.
I suggest a pipe wrench on rounded hex bolts because of their geometry that grabs bolts when turned correctly.
~Nate

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95 Honda Shadow ACE 1100.
1999 Plymouth Neon Expresso. 2.4 swap, 10.5 to 1 comp, big cams. Autocross time attack vehicle!
2012 Escape, 'hunter" (5 sp 4cyl)

Any way to weld a good bolt to it so you can turn that one?

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

Kroil is far better than PB blaster. Start with that and let it sit for a bit- 24 is best with multiple applications, then a sharp strike and whatever you can use to hold the bolt head to loosen it.

have you applied heat?

No heat yet but I might be able to get a Mapp torch on the alternator ear where the bolt is threaded. I'll look into that.
A pipe wrench isn't going to work. The head is one of those bolts with a built in 'washer' at the bottom so it has a slight taper to the bolt head. Plus 8" of torque isn't going to cut it. I've put a fair amount of muscle into it with an 18" breaker bar and it hasn't budged. It took the 18" breaker bar to get the nut on the AC adjuster system to loosen up also. Must have been a hefty guy who last cranked them down.
I'll see if I can find some Kroil at the parts store.
Welding may be possible but I'm a little concerned about welding on the alternator bracket.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Probably no way to cut the bolt head off. I can't tell from the picture if there would be room to get in (radiator in the way, etc.).

I sometimes use my thin cutting wheel on the angle grinder to cut the head off but you still have the ordeal of 'easy-outing' the bolt. It usually comes easy, with the tension taken off.

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1986 300SDL, 362K
1984 300D, 138K

http://www.sears.com/shc/s/p_10153_12605_00952060000P?sid=IDAx20080403x000001&srccode=cii_18492716&cpncode=22-104350402-2


This is just one of several bolt out sets Sears sells. You're accessibility is limited - I would think a socket desgned for this situation would be best.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

any chance its a left handed thread?

if not I like the use of heat

I bought that set today. It's next on the list of tools to try.

Accessability is very poor. If I cut off the bolt head I'll still have to pull the alternator and I'm not sure how easy it will be to get if off the adjuster even with all the other bolts removed. Not sure I can get a Dremel tool in there at an angle which would allow the head to be cut off without removing the radiator. The picture is deceiving with the radiator and shroud removed. There's just enough room between the belts and the shroud to get a ratchet in there.
The radiator may have to come out. It's got a plastic tank and I discovered a crack today. (as if this rounded bolt wasn't bad enough). I patched it with SuperMend epoxy and S-glass. If that doesn't hold I'll have to replace it.

Everything else is standard thread and from what I read, this is standard thread too. I did try tightening it to see if that trick would break it free but that didn't work either.

By the way, I did try an extractor socket I bought in a set at Pep Boys. The socket has about 6 pins in it. Worthless junk.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

My favorite machinist will get a stuck bolt red hot and put candle wax on it. The heat sucks the wax down into it and voila, out it comes!

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I second those rounded bolt outs at sears. They work well.

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1985 CA 300D Turbo , 213K mi

I like that one, will try it the next time when I have this problem. But to avoid rounding bolts I trashed all my 12 point sockets and replaced them with 6 point sockets.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).