Broken Bolt - best way to deal with it

Yesterday while we were trying to change the thermostat on a '92 TS GT 3.8L V6 MPI disaster struck - one of the two bolts holding the thermostat housing broke in the aluminium base.

Now there's a little bit left of it left above the surface (5 mm). Can you please advise on what's the best on-site method for getting it out - we don't have access to a welder where this happened?

For the future - is there any way to prevent this from happening when working with corroded-in bolts and bits?

Many thanks!

Very unfortunately, I had the same experience. I tried even heating the bolt with mapp gas and dousing it with cold water to get it loose. I even used a pipe wrench on it with no success. MY friend came over and was absolutely confident he would get it out. He wanted to use an easy-out against my experience with their success. I implored him to not snap off the easy out when I was gone for a short while. Needless to say(he snapped off a big one), eventually I had to remove the mounting corner of the thermostat housing on the intake manifold, use a heli-coil, and J-B weld the corner back. It holds, but I cannot
tighten it properly.

I would REALLY(intuition prior) consider drilling out the old bolt and tapping it to a larger size if need be. I was told by a very good mechanic that easy-outs work on new installations best. Our problem is that we are dealling with dissimilar metals that have corroded. I have never had a bolt so frozen into another part like this before. I have also NEVER had luck with an easy-out (40 years driving)...GOOD LUCK

Yes, once an easy out breaks, it's basically all over.....

Have used PB Blaster to soak the frozen threads....may take 24 hours with multiple applications....then shock the bolt by hitting drift pin in the center....if it sticks slightly above the surface, use a cold chisel on the outside edge and drive the thread CCW.....it may loosen and come out....if it doesn't or it's not enough above the surface, drill out with LEFT-HANDED drill bits.....sometimes it backs out as you drill...otherwise drill out and re-tap.....heli-coil if necessary.....

There's nothing "easy" about them. Drilling a proper sized,centered hole is the key. And soaking them long enough too as previously mentioned.

Although I have encountered my share of mechanical problems over the years, I am not a certified mechanic. Tech II obviously knows the answers for this nasty problem. I tried PB blaster. My friend used a chisel to try to back it out after he snapped off a a large easy out. What I found out from a pontiac mechanic friend is that the two dissimilar metals make this job that much more difficult. Obviously, the corrosion really binds these two metals. I cannot tell you guys how much agony I had over this experience.

With a bit protruding, you might be lucky and get it out with a small pipe wrench or vise-grips, just careful not to damage the mounting surface. Failing that, try to tap out the bolt with a small sharp cold chisel, tapping counter-clockwise around the edges. failing that, grind a flat spot on the top of the bolt, and use a center punch to pop a spot exact center, use small drill to start a hole. Be careful, I think it is a blind hole, don't want to drill into water jacket, and gradually use larger drill until very close to touching threads. Use a small punch to push remaining bolt into center of hole, and pick it out, possibly in pieces. You may wish to remove throttle body to get clear access; if you haven't already done so, drain coolant as coolant does circulate through the body; at least it does in my 95
Good Luck, not fun... Jeff

Getting ready to take this slow and painful...

In case we get it out in the end - does anyone know an online store where I could find a similar bolt to replace the broken one (had a look on eBay and GMpartsdirect with no luck in Thermostat Housing Bolts).

Thank you!

Just a 10mm bolt? Bring the other bolt to a hardware store to compare length and pitch.....

AND...when you bolt back in...either with the original threads or enlarged thread...use anti-seize compound....just like with spark plugs in aluminum heads.......it might help the next time....if any...

Thank you all for some great ideas. Good point LMP!

I'm starting to grasp the potential for disaster of this combination (steel bolts in aluminium mounts...).

We'll make sure the new thermostat holds for a long time. ;)

Wonder what will take to get a bolt factory-threaded in aluminium out in one piece next time...

Wonder what will take to get a bolt factory-threaded in aluminium out in one piece next time...

A lot of patience, a lot of WD-40, a lot of fiercely tapping on the head of the bolt to break the "rust" and then wisdom, and gently trying to remove the bugger :)

This is the agony of all owners who maintain their own cars and have cars with aluminum and steel parts connected to each other. :naughty:

Tapping.. You mean hammering the bolt to "shake" things up?

Tapping.. You mean hammering the bolt to "shake" things up?

Correct.
It doesn't always help, but it may help in your case.

I had a broken bolt on the waterpump of my DeLorean.
I sawed a slot into the remains of the bolt, but it was so firmly frozen that one of the sides of the slot broke.
The piece still reachable had to be equalized before drilling it out.
The spot where I had to drill could anly be attacked with an angled drill.
Not fun to do and almost a guarantee for being not fully centered.
Fortunately there was an open space behind the bolt's hole in the engine block.
It allowed me to drill a bit oversized and use an oversize bolt and nut to ensure proper tightening of the waterpump.

I haven't looked at the place you have to work in, but I do not envy you.
It's a job I hope to have done only once.
Wish you lots of wisdom and luck.

Had a similar problem with 2 out of 3 bolts broke, see AF http://www.automotiveforums.com/vbulletin/showthread.php?t=1080650

Problem solved with a lot of heat (propane torch), WD-40, patience and a few heart-felt prayers.

Now comes in handy all the advice about preventing this sort of agony from repeating itself.

Thank you all for the useful ideas and support in handling this issue!

P.S. I'm starting to hate engines with steel and aluminum parts bolted together.

Glad you were able to remove that bolt. I had a nightmare from that ordeal.
I can easily remember using a pipe wrench, mapp gas, pb blaster, etc. My problem bolt became one with the intake manifold. ;-) cheers KEV

Problem solved with a lot of heat (propane torch), WD-40, patience and a few heart-felt prayers....
COngratulations....sure we are all relieved that it turned out a success.

In some cases you can spot weld a flat washer on stud 1st, than spot weld a nut on top.

I have had my share of stubborn bolts. I have never seen a bolt take as much torque using a pipe wrench as this one. I received good advice about heating it up with mapp gas and dowsing with cold water from a Chrysler mechanic.
A patient of mine uses a TIG welder to spot weld a nut on top of the bolt while having a mechanic work it while it is cherry red. He has all the right tools for extraction. Unfortunately, I am just a home garage mechanic. I am just very grateful our Transport has lasted so long. Cheers and good bye to this nightmare for you and me...KEV

P.S.- LMP's recommendation of silver anti-seize is taken seriously by me. Especially on lug threads!!

Here's what you guys are talking about.
http://www.youtube.com/watch?v=nIJIVZpZZIw