Broken Thermostat housing bolt

[Timothy B.]

Today I decided to change the antifreeze on my 67 327/300 and install a new thermostat. When I tried to loosen the thermostat bolts the one on the right side broke off leaving about 1/4" sticking up. I have sprayed it with WD40 and still can't break it loose using vice grips. I CAN JUST SCREAM but I thought it better if I got the opinions on the D/B first. I am concerned I will not drill straight and then really have a problem. Any advice is appreciated. Thanks very much Timothy Barbieri

[Mike M.]

Re: Broken Thermostat housing bolt

remove intake so you can drill it out in a drill press where you are assured of drilling parallel to the long axis of the broken bolt. first you'll have to grind the exposed 1/4" of remains level, then take a small punch and dimple the CENTER of the remains then set up intake so it's thermostat mounting face is perpendicular(exactly) to the drill bit.then buy a drill bit with left hand rotation. by drilling counterclockwise with the left hand bit, often times the heat generated by drilling process, along with the counterclockwise forces impacting on the broken bolt , will loosen it and it'll come out on the bit. snap=on sells a set of left hand bits, part #DBLS 105. i've found them invaluable. if that doesn't work, try an easy out(i usually don't have good luck with them, even the fancy snap-on varities). if that doesn't work you could try a helicoil but coolant seepage a likely side effect of helicoil. last resort is buying another intake which shouldn't be too hard to locate as i'm faily certain the 67 pass car 327/300 used the same intake as the 67 vette 300 hp small blcoks. good luck, mike

[G B.]

Do you own a torch?

I would remove it with the intake left in place, but I've done it before.

You will have to use very high heat on the cast iron all around the broken bolt. You'll also have to grind two "flats" on the exposed 1/4" stub so a large crescent wrench can twist it. Actually, I would lock on vise-grips vertically and then use a huge crescent wrench to turn the vise-grips. Don't try to twist out the bolt stub until the iron around is extremely hot. You're really sunk if that 1/4" projection gets twisted off.

The toughest part will be keeping the heat from harming anything. I recommend having a helper with a spray bottle of water keep the near-by metal relatively cool. You definitely want to keep the seal between the intake and the block from cooking. I would remove the carb and gas line completely.

If you've never used torch heat to expand the diameter of a threaded hole, please don't try to learn now. Pay someone who knows how to do this safely.

[Gary S.]

Re: Broken Thermostat housing bolt

Forget WD40 and try some PB Blaster, letting it soak for an hour. Spray the PB Blaster and then LIGHTLY tap the bolt head. Spray one more time, let it sit and then follow the directions the others have given you. WD40 is not a penetrating oil of any consequence. You can get PB just about everywhere.
Gary

[kelly theaker]

Re: Broken Thermostat housing bolt

heat is the answer, just use a bit of heat , then make a purchase on the bolt once , i mean make a good puchase, then rotate the bolt to the left , once you break the bolt loose, just rotate slightly to nleft then back to the right then apply the juice and rotate a little further to left then back to right , dont get greedy. A torch is the answer. but as the site has said juice is sometimes all that is needed. or the drill. usually a lot more work and sometimes looks butchered.

[Ronnie Robertson # 36786]

One last try...

Tim,
Clean the area around the bolt with a small wire brust. Heat bolt and surrounding area well with a propane torch, but not red hot. Apply wax from a candle- any kind, any color. It will melt, smoke, etc. With the bolt still hot,apply force to bolt with vice grips. Steady force and hold it. Repeat if necessary. Works for me, every time.
Good Luck

[Joe L.]

Re: Broken Thermostat housing bolt

Timothy-----

If all other suggestions fail, then remove the manifold and locate a machine shop in your area that has EDM (Electro-Discharge Machine) capabilities. Not many automotive shops will have this capability, but better shops that specialize in industrial work will have it. Using EDM, the bolt remnant can be "pulverized" and removed.

[kelly theaker]

Re: Broken Thermostat housing bolt

i should have mentioned in earlier post that if you do apply head andf twist of the remaining bolt , then put a nut over the broken stud and mig the center of the nut to the broken bolt and leave for a night , you will be surprised with the results.

[Terry F.]

Re: Broken Thermostat housing bolt

Helicoil is a popular fix and I have used them a lot. But, better than a helicoil is an insert. They are specially made for replacing threads that are under significant stress/tension. Esentially, you drill out the stipped treads, tap it and screw the insert it (like a helicoil but not a spring). You use loctite to lock it inplace (special loctite). It is as good as new in most cases. Much better than a spring. The insert sort of looks like a tube with threads on the inside and outside. You can purchase them in all sorts of exotic metals, cast, steel, hard steel, stainless, etc. Once it is in place you grind it flat and it is as good as new. Terry

[Chris S.]

Re: Broken Thermostat housing bolt

The wax tip above works !!

[Gary Bishop]

Re: Broken bolts Web Site

http://www.stovebolt.com/techtips/brokenbolt.htm

[Chuck R.]

Re: Broken Thermostat housing bolt

If you have issues with torches and welders, try this.

Soak the stud with penetrant.

Drill out the stud as close to the manifold threads as possible without hitting them.

Keep stepping up in bit sizes until you get where you want to be.

If you attempt this on the car, be extreemly careful not to waggle the drill motor from side to side. The last thing you want is a snapped off drill bit in the stud.

After the stud is drilled out, cut cross slots accross the stud, down as close as possible to the manifold surface.

With the corner of a small, sharp, hand chisel and a small peen hammer, GENTLY start to work the notched edges of the stud inward and at a slight counter clockwise angle at the same time.

Sometimes, the bolt will loosen up before you get very far, so keep checking it.

If you have a heat gun, all the better

You can apply a ton of heat to the surrounding manifold to get it to expand away from the bolt before you start chiseling.

It's been my experience that easy outs arn't good for much except very very low stress light duty applications.

By the way, is this a performer type aluminum manifold or the original?

Hope this helps,

Chuck

[Terry F.]

Re: Broken Thermostat housing bolt

My suggestion is only a last resort when the threads have been trashed. I like the wax idea and look forward to trying it. I like the washer idea also because of how it works. I like using heat and have found that it works well for me. It also dissolves rust. Aluminum is another story. I have found that if something gets stuck in aluminum for whatever reason (corrosion)if you do get the bolt out it seems to take some of the threads with it. Next time you try to tighten down into it they just don't feel the same. Very limited life. Terry

[Timothy B.]

Re: Broken Thermostat housing bolt

I want to thank everyone for responding to my post. This is the original manifold on my 67 and I want to be careful not to damage it. I have put PB blaster on the stud and I'll try to break it loose tomorrow, after that I will try the wax and if that dosen't work I will resort to the torch. If no luck then I will remove the manifold and have a shop remove the stud. I will let everyone know how I make out. Thanks again Timothy Barbieri

[Terry F.]

Re: Broken Thermostat housing bolt

I think WD40 is cheap diesel fuel with a rust preventative. Terry