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88v8
Ivor Duarte
Gloucestershire UK
(629 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Broken bolts in alloy
Posted by: 88v8
Date: February 18, 2016 05:22AM

You know how it is. A simple job, ten minutes.
Going to change the thermostat. Four bolts into the alloy housing.
Gently with the spanner.
Ping! Head gone.
Try another one.
Ping!
Arrrgh.

So now, out with the blowlamp, MAP blowlamp, and a point & shoot thermometer so I can see when things are hotting up.
Next one comes out, hooray.
UNF thread. You'd think Rolls-Royce with all their alloy experience would have known better than to put fine thread into alloy.

Last one.... ping!
I heated to 170F, maybe not high enough or long enough.

So now I have three 5/16" seized stubs to get out.
Reason I'm posting is that this must be a pretty general problem, and I'm hoping you have some cunning plans I haven't thought of.

What I intend.:

Plusgas, leave a day.
File the top flat, not flush but flat. Pop and drill about 7/64".
Now cut a small step in the edge, and use that as a point of purchase so I can rotate it out by tapping tangentially with a blunt chisel. Heating meanwhile.
If that fails, Plusgas, leave a day.
Then use the hole as a point to inject plumber's freeze spray, so I'm heating the alloy housing, and cooling the stub, then tap it some more. This sounds easy, but judging the boundary between heat and cold is hit and miss, and if I overcool the stub it could shatter.
If all else fails, drill it out some more and use Easy-outs, surely the most misnamed tool of all time. I have doubts about this, as in my experience it's hard to get an accurate centring when working freehand, and anyway, the Easyouts have a tendency to snap in the hole.

Other than not having started the job in the first place, any magic ideas?

Don't have a welder.

I could also use magic for my Rover V8, where some of the water pump bolts are going to snap off if I ever try to disturb them.
Alloy engines, don't you love them.

Ivor


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1056 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Broken bolts in alloy
Posted by: ex-tyke
Date: February 18, 2016 09:06AM

Bolts should have had high heat before removal attempt.
If all else fails, I'd drill out the remaining studs and retap with NC threads (even if you have to use helicoils to repair a damaged area)
Bottom line is that the housing can be salvaged.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5759 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Broken bolts in alloy
Posted by: BlownMGB-V8
Date: February 18, 2016 12:05PM

It's not easy but can be did. Aluminum melts at around 1200 F so you can heat it up to around 900 without worrying too much. If you can deposit some carbon on it (yellow flame of any type) you can heat until that burns off and that's about right. At that temp your bolts should turn out easily.

Jim


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Broken bolts in alloy
Posted by: DiDueColpi
Date: February 18, 2016 12:47PM

Here's what usually works for me Ivor.
Before you even try to remove a suspected stuck bolt, give it a couple of good raps with a hammer. (only if the piece can handle it of course) This is to shock the bond between the two parts and hopefully free them up. Next is to soak the area in rust penetrant and let it sit. A couple more shots from the hammer to help the penetrant wick into the joint is also helpfull.
If you can, use an impact driver with a suitable socket to loosen the bolt. The idea here is to use a socket that rests on the mating area or flange and briefly compresses the joint while you attempt to loosen it. Once the bolt starts to move, work it back and forth to slowly remove it a bit at a time. Patience is the key here.
If the bolt has broken off. Resist the urge to weld a nut to it. While this does work very well in some cases, if it doesn't you are left with a broken / hardened bolt that is extremely difficult to drill out.
File the bolt flat. Center punch it and drill an 1/8th inch hole all the way through it. Now you can try heat. Heat the bolt only, as hot as you dare. Use drops of engine oil on the surrounding metal to check temp. If they smoke and burn off rapidly then you are as hot as needed with aluminium. What you are trying to do is expand the bolt. Once it cools and contracts it will hopefully have broken the bond enough to come free. Next fill the hole with penetrating oil and start drilling the hole larger in small increments until you are as close to the thread size as you can get. Drilling in small steps lets you correct for off center as you go. Now you can use the largest bolt extractor that will fit. Be careful because a broken off extractor is a whole new kind of misery.
If the extractor doesn't provide any joy, grab your Dremmel or die grinder and carefully grind away until you expose the root of the threads. With a pointed punch carefully chip away at the remaining threads. Once done chase it with the appropriate thread chaser and your good to go. It's a bit tedious but you are left with an original part and the original threads.
If it all goes to hell in a hand basket, a helicoil is a perfectly good option in most cases. Just make sure it goes in straight and isn't close enough to an edge or sealing surface to cause problems.

Cheers
Fred


Dan B
Dan Blackwood
South Charleston, WV
(965 posts)

Registered:
11/06/2007 01:55PM

Main British Car:
1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl

authors avatar
Re: Broken bolts in alloy
Posted by: Dan B
Date: February 18, 2016 05:33PM

Fred, I have seen my brother Jim do exactly what you describe. You are right about it being tedious!


minorv8
Jukka Harkola

(144 posts)

Registered:
04/08/2009 06:50AM

Main British Car:
Morris Minor Rover V8

Re: Broken bolts in alloy
Posted by: minorv8
Date: February 19, 2016 07:02AM

Quite often it is not the treaded section but the shank of the bolt that gets stuck. I have sometimes simply broken the housing to reveal the sheared bolts or studs. Of course this is not an option it there is no spare available :-)


waterbucket
Philip Waterman
England
(70 posts)

Registered:
07/30/2011 01:08PM

Main British Car:
1978 MGB GT

Re: Broken bolts in alloy
Posted by: waterbucket
Date: February 19, 2016 10:36AM

I would go along with what Fred has said but with another variation, I would get a set of left hand drill bits, drill the 1/8 hole as per Fred .If this does not remove the broken stud/bolt, heat and let the penetrating oil soak overnight, then drill one size larger. As you are drilling there is an equal and opposite reaction and the stud will be trying to unscrew. I have used this method several times and it still leaves the option of using a using a stud extractor as a last resort or continuing drilling until the threads show. There is a possibility that if the next drill size is too small an increment then there will be insufficient reaction to undo the stud.
regards Philip



88v8
Ivor Duarte
Gloucestershire UK
(629 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Broken bolts in alloy
Posted by: 88v8
Date: February 19, 2016 05:01PM

Mmm, never had left-hand drills. I ought to buy a set. I'll put them on my shopping list.

Got one bolt out today.

Yesterday I levered the stat housing off, even that was corroded onto the bolt stubs and I had to heat it.
Then left the bolts - actually, setscrews - soaking in Plusgas overnight.

Today, out with a small blowlamp, heated the stub then left it an hour. Then, the MAP blowlamp and heated the alloy housing to about 450F this time, that seems to be as far as I can get with this blowlamp as the alloy inlet manifold leaches the heat away.
Was tempted by the length of stub, so I put a good Mole wrench on it and still heating, very carefully started to turn it out. After a couple of minutes heating and twiddling, out it came.

To get at the back pair of stubs I need to remove the stat - guess what, it's stuck fast grrr. I heated it and the housing until the fusible plugs melted, and levered at it, but it's still stuck.
More Plusgas.

Tomorrow is another day.

Ivor


pcmenten
Paul Menten

(242 posts)

Registered:
10/08/2009 10:40AM

Main British Car:


Re: Broken bolts in alloy
Posted by: pcmenten
Date: February 19, 2016 08:28PM

I keep searching the 'net for a suggestion about using electrolysis to treat the corrosion of the threads. My thinking is that it might be possible to reverse the chemical reaction at least a bit. Nothing definitive yet. I'm just not sure which part should be the anode and cathode.

Edit: Try attaching the negative side of a D cell battery to the steel bolt and the positive side to the aluminum.



Edited 1 time(s). Last edit at 02/19/2016 08:44PM by pcmenten.


roverman
Art Gertz
Winchester, CA.
(2974 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Broken bolts in alloy
Posted by: roverman
Date: February 20, 2016 04:19PM

So as you drill, ever larger with your LH. bits, it is also relieving "some" pressure. If you select the right interference fit, LH bit, you "might" tap it in the hole and use it as an extractor. For extractors, I like Proto Blackhawk/etc.,(4 flute with aggressive positive rake) on the flutes. These grab better than the spiral types. Consider replacing bolts/studs with stainless ? Cheers, roverman.


88v8
Ivor Duarte
Gloucestershire UK
(629 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Broken bolts in alloy
Posted by: 88v8
Date: March 10, 2016 06:16AM

Got them all out by the same method. Lots of heat.
The stat itself was so stuck that I not only had to heat the housing, but at the same time spray the stat with plumber's CO2 spray.

The three larger bolts - 5/16" - the UNF threads in the alloy housing were OK, but the smaller bolt - 1/4" - the thread was part stripped so I drilled right through the housing and made a much longer thread.
On replacement, I put Hylomar Blue on the bolt threads to try and seal them against damp.

All well now.

Many thanks for all the advice.

Ivor


Beau Dirt
Beau Dirt
Minneapolis, MN
(35 posts)

Registered:
05/02/2012 03:23AM

Main British Car:
1973 Morris Mini, 1930 ford Model T, 1926 Model T 1 liter Suzuki and Four 215's

Re: Broken bolts in alloy
Posted by: Beau Dirt
Date: April 16, 2016 11:14AM

I had this problem. I grabbed a hand full of nuts about the same size hole as the bolt. Hold the nut up to the busted bolt head and weld the nut on to the broken bolt. The heat from the weld helps heat up the bolt and you have something to put the wrench on.


88v8
Ivor Duarte
Gloucestershire UK
(629 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Broken bolts in alloy
Posted by: 88v8
Date: April 17, 2016 04:50AM

Yes. In my mis-spent youth I should have learned to weld.
Heyho.

Ivor


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