Removing Stuck /Broken Bolts

CandBMotorworks

CandBMotorworks

C&BMotorworks
I don't know about the rest of you, but it seems to me that FIATs used a very special metallurgy for their "steel" bolts. Anything bolted to the engine has pretty much welded itself to the aluminum, and for me at least, no amount of penetrant seems to be helping to break that bond. Meanwhile, it takes almost no effort to get a bolt to shear.

I recently removed the bolts securing the fuel injectors on an 87 Bertone. One of the heads sheared off. After removing the injector I had exposed bolt and attempted to work it out only to have it shear again. I am now looking at having to drill it out.

I imagine others have encountered this problem that seems unique (for me) to FIATs. Please offer your suggestions for (a) how I get the remainder of this bolt out without ruining the aluminium it has adhered itself to, and (b) what you do to get the old bolts and nuts on these cars to work as intended instead of rounding/shearing.

Thanks in advance.
 
Not about Fiat, this is a given problem for ALL plated fasters into aluminum. Aluminum is a poor material for threaded holes. Extremely common and has worked ok in millions of mechanical devices, but this is NOT the ideal combo.

Aid to this problem is anti-seize, moly or nickel anti-seize goes a long way to reducing what happened. This is extremely recommended for commercial stainless steel threaded fasteners due to the great tendency for stainless steel fasteners to gall, then essentially weld itself into the mating stainless steel fasteners. Alternative to anti-seize is loctite. This acts as a surface filler to prevent the joint from vibrating loose and reduce the tendency for these surfaces to gall.

The aerospace industry does silver or moly or similar coated threaded fasteners to address this problem. Aerospace spec threaded fasteners also have a spec for thread surface finish which goes a long ways to preventing galling. One of the many reasons to use Aerospace spec fasteners where possible.

Question is.. how will that broken off threaded faster be removed? Think over how to remove very carefully as the consequences of applying improper actions can be devastating. This was how a broken off M6 screw was removed from plastic trim on# 209.

Broken screw removal.

Took apart the nose on the x1/20 to fix corrosion in the battery box area. The side nose trim pieces had to come off to gain access to that area of the nose. Both M6 screws snapped off with a modest tug of a 10mm wrench even after being soaked in penetrating oil for a few days. Both screws had...
xwebforums.com


Bernice
 
I've had decent luck dissolving broken steel fasteners and taps out of aluminum by submerging the part in a mixture of battery acid and alum powder and leaving it for several days. Lightly heating it speeds up the process.

Like a sacrificial anode in a water heater, the steel dissolves first. I would avoid doing this to precision machined aluminum surfaces because the aluminum parts usually see some very minor surface corrosion.

This method only works with steel in aluminum.
 
Rupunzell said:
Not about Fiat, this is a given problem for ALL plated fasters into aluminum. Aluminum is a poor material for threaded holes. Extremely common and has worked ok in millions of mechanical devices, but this is NOT the ideal combo.

Aid to this problem is anti-seize, moly or nickel anti-seize goes a long way to reducing what happened.
Bernice
Click to expand...
Bernice included some very good information here. Just one minor correction. Technically what's happening between the aluminum and the plated fastener in this case is galvanic corrosion.
This is a common problem when assembling things with dissimilar metals. The anti-seize does keep galvanic corrosion from happening but it's not the same as galling, which is common with stainless steel fasteners. What the anti-seize does for aluminum and plated fasteners in this case is it keeps the electrolyte away from the two materials so they don't corrode.

Removing the fasteners you can try to dissolve the corroded aluminum. Muriatic acid or ammonia May help dissolve some corrosion to loosen up the fastener a little bit. But be careful with harsh chemicals.

It's not a Fiat issue. The problem is chemistry of using aluminum and plated fasteners.
 
Last edited:
I hadn't thought of muriatic acid. I was wanting to avoid anything that would damage the aluminum, but it sounds like the consensus is that this will be ok. Battery acid and aluminum powder aren't readily available for me, and I'm not certain that I'd be able to submerge the broken bolt in any mixture since it sits on top of the engine at the moment. Also, will this damage the threads? (FYI, I believe this is an M4 bolt that I am attempting to remove.)

While I understand what you are saying about this not being a FIAT problem, I haven't encountered bolts shearing with any other car I've worked on (Audi, VW, Honda, Porsche, Triumph, etc.). I have encountered stuck bolts, but have not had one shear in any other car. That was the point of my comment about the "unique" nature of FIAT metallurgy.

A couple of you have said "plated" with regard to the bolts. When I hear plated I think of chrome plating, nickel, or the like. I don't believe these steel bolts are plated, though they are dark. Can someone educate me on this?
 
Don't forget, heat always helps. Aluminum will expand at a much faster rate than steel, and hence, may allow you to break a bit of the galvanic corrosion which is hold it in place. I would be prepared to take it to a machine shop to have them deal with it. Unless you happen to have all the right tools, the cost of trying to do it yourself, i.e., your time, what you have to buy, etc, will probably exceed the bill from a machine shop. Also, if they screw it up, then they can fix it with a helicoil, which in the end is a better mechanical grip anyways. It's also lighter than original, so you can tell your friends you had the head lightened. hahaha.... Let us know what you end up doing.
 
Aluminum to Zinc is not that far apart on the Galvanic scale. Cadmium is better than zinc to aluminum. Worst is stainless steel to aluminum.

Metal Compatibility | Galvanic Corrosion Scale

Galvanic Corrosion Scale - to help evaluate the susceptibility of two metals in contact to galvanic corrosion. Links to related information.
www.mfcp.com www.mfcp.com

Far awful is aluminum to titanium as they are so far apart on the galvanic scale.

If the screws in question are the M4 socket heads that hold down the injector clamp, those are black phosphate steel, essentially bare steel that will rust unless oiled. If they are stuck, the problem is more likely moisture getting into the threaded area causing rust, rust expands into the threaded area essentially locking the threads together.

If acid or citrus based cleaner (simple green, which is acidic) is applied to aluminum, do this with great care as the acid will etch then slowly eat away at the aluminum until pitting and worst damage is done. Corroded surfaces results in a different kind of problem, known as Stress Corrosion Cracking.

Different Types of Corrosion: Stress Corrosion Cracking (SCC) - Causes and Prevention,WebCorr Corrosion Consulting Services, Corrosion Short Courses and Corrosion Expert Witness

Different Types of Corrosion: Stress Corrosion Cracking -Causes and Prevention. All Different Forms of Corrosion are explained by NACE certified Corrosion Specialist . WebCorr provides corrosion consultancy services, corrosion expert witness and corrosion short courses for in-house training...
www.corrosionclinic.com

Keep in mind castings are often porous allowing stuff to be absorbed into the aluminum casting that could cause problems in the future.

Goes back to the proper use of anti-seize or loctite, attention to fastner materials used and all those details often neglected or forgotten.

As for hardware on other brands.. they all pretty much bust the same. What has improved in much newer cars and other mechanical widgets, the type of zinc and other corrosion resisting coating have improved LOTs..



Bernice
 
fastx19 said:
I would be prepared to take it to a machine shop to have them deal with it. Unless you happen to have all the right tools, the cost of trying to do it yourself, i.e., your time, what you have to buy, etc, will probably exceed the bill from a machine shop. Also, if they screw it up, then they can fix it with a helicoil, which in the end is a better mechanical grip anyways. It's also lighter than original, so you can tell your friends you had the head lightened. hahaha.... Let us know what you end up doing.
Click to expand...

If there is an attempt to drill out the broken screw, the odds of succeeding with a M4 screw is not good at all. What tends to happen, the rough surface of the broken off screw will cause the drill to wander off into all various directions with the side of the broken off screw against the aluminum as the drill's guard rail. Center punch can help reduce this, question is how to get on-center with the center punch then making sure the drill is absolute parallel as the broken screw is being drilled out.. Left hand drill highly recommended as there is a chance the drill might snag then un-wind the broken screw out.

It might be better in many ways to take the part with the broken screw directly to a competent machinist to have it removed. Chances for removal is better if the broken screw is un-molested and there is a better possibility of preserving the original threads instead of applying a helicoill or similar thread repair.

Bernice
 
Last edited:
The manifold can be removed to make it much easier to access the offending fastener. I got lucky with the same exact problem and was able to soak and then use a cold chisel to rotate it out. Not much to grab there.
 
Grind the surface of the bolt flat, center punch the center. Drill with cobalt drill bit, careful, break the brill in the hole and you will create a bigger problem. Once out, re-tap the hole. Ideally you just drill the bolt, leaving the threads of the bolt in the hole, if the hole gets to big, then you are stuck using some type of threaded insert. Mcmaster Carr has drills, taps and threaded inserts.
Always use some anti-seize on aluminum or stainless threaded parts.
 
CandBMotorworks said:
I don't know about the rest of you, but it seems to me that FIATs used a very special metallurgy for their "steel" bolts. Anything bolted to the engine has pretty much welded itself to the aluminum, and for me at least, no amount of penetrant seems to be helping to break that bond. Meanwhile, it takes almost no effort to get a bolt to shear.

I recently removed the bolts securing the fuel injectors on an 87 Bertone. One of the heads sheared off. After removing the injector I had exposed bolt and attempted to work it out only to have it shear again. I am now looking at having to drill it out.

I imagine others have encountered this problem that seems unique (for me) to FIATs. Please offer your suggestions for (a) how I get the remainder of this bolt out without ruining the aluminium it has adhered itself to, and (b) what you do to get the old bolts and nuts on these cars to work as intended instead of rounding/shearing.

Thanks in advance.
Click to expand...
Betcha a trip to the machine shop is a lot more than getting good used from Midwest-Bayless:
www.midwest-bayless.com

Intake Manifold Runner Left (Fiat Bertone X1/9 1980-88) - U8

Intake Manifold Runner Left (Fiat Bertone X1/9 1980-88) - U8
www.midwest-bayless.com www.midwest-bayless.com
www.midwest-bayless.com

Intake Manifold Runner Right (Fiat Bertone X19 1980-88) - U8

Intake Manifold Runner Right (Fiat Bertone X19 1980-88) - U8
www.midwest-bayless.com www.midwest-bayless.com

Or asking in FS&W if anyone has an extra of the side you need. Carl hates FI, he probably has a couple laying around the garage :)

If you want to try removing the broken capscrew, I would not try to do it in place, I'd pull the runner off the head***. The neat thing about doing work on the runners is that they are intended to bolt to something, so you could easily fab up a piece of steel and bolt the runner to it, then use the steel to secure the runner into a drill press (a Bridgeport would be da bomb), giving you a nice sold base to hold the work at the desired attitude.

***Note that the FI manifold gaskets seal vestigial coolant passages in the head, so removal of manifolds will cause coolant drips unless you lower the level in the head a bit before separating them from the head.
 
Last edited:
I'm not sure I would recommend the use of acid to "dissolve the broken bolt in aluminum" suggestion. But it's a personal choice.
 
FWIW, this isn't the first time this has happened to me. The last time it was on a different 1500 and the bolt connected the t-stat housing to the head, IIRC. As I recall we drilled it out, welded up the hole with a TIG welder, and then redrilled and re-tapped the hole. It was a royal PIA and I was hoping the feedback here would help me avoid that scenario.

It sounds like the growing consensus is to pull the intake and have it drilled out by a machine shop.
 
I'd definitely begin by pulling the intake portion with the broken bolts. Makes it much easier to work on. Then decide if this is something you can drill out and install thread-certs yourself, or have a shop do it. If I'm not mistaken you guys are doing Fiat servicing so it might be worth the investment to but the kits for installing thread-certs (Helicoil).
 
I've used diluted phosphoric acid (literally, Coca-Cola) to attack the galvanic corrosion between steel studs and an aluminum manifold. About three days of soaking
 
Rounding or breaking the allen head cap screws that hold the fuel injector retainers and blocks is not unheard of here, in situ they are hard to get to with odd angles, have the dissimilar metals issue, and are typically an ignored maintenance item so are in-place for decades at a time. And most don't realize that the best way to do service on the injectors and hoses themselves is to separate the plenum from the runners, that's why they are separate and that's why the fuel rail is mounted to the plenum with horseshoe-shaped bracketry.
 
Last edited:
CandBMotorworks said:
FWIW, this isn't the first time this has happened to me. The last time it was on a different 1500 and the bolt connected the t-stat housing to the head, IIRC. As I recall we drilled it out, welded up the hole with a TIG welder, and then redrilled and re-tapped the hole. It was a royal PIA and I was hoping the feedback here would help me avoid that scenario.

It sounds like the growing consensus is to pull the intake and have it drilled out by a machine shop.
Click to expand...
I have ran across a lot of frozen bolts in aluminum.
Alloy wheels that have been on steel hubs for a long time tend to corrode up and can be a pain to remove.
This is because the two different metals are like plates in a battery and when moisture is added it causes electrolysis.
Getting a corroded bold out of a piece of aluminum usually leaves a messy hole in the aluminum.
Welding, drilling and re-tapping is probably the best way but in my early years of shade treeing I have had bad luck tapping aluminum and wound up with a mess.
I try to avoid tapping aluminum and to this day I break into a cold sweat it I have tap threads in aluminum.
If you try it on your own invest in a new tap, go slow and have plenty of patients otherwise a machine shop could save time and money in the long run.
 
I doubt this helps, but you may get lucky with an extractor bit as I did once - a few years ago I had a head bolt in my 850 Spider that sheared flush with the (iron) block. Center-punched it and used a handheld power drill to remove most of the bolt material, tried a couple of different brands/styles of screw extractor and found that one of them got some bite inside the hole (unfortunately I can't remember which was the winner, may have been an Irwin?). Extracted the bolt and once it was out saw that what remained was the thinnest of shells, by beginner's luck I had drilled it out exactly in the center, didn't even nick the threads in the block. Was so amazed at my good fortune I ran across the street with the remains of the bolt to show it to my neighbor/Alfa mechanic Tim Rooney.
Maybe you'll get equally lucky?
 
CandBMotorworks said:
I don't know about the rest of you, but it seems to me that FIATs used a very special metallurgy for their "steel" bolts. Anything bolted to the engine has pretty much welded itself to the aluminum, and for me at least, no amount of penetrant seems to be helping to break that bond. Meanwhile, it takes almost no effort to get a bolt to shear.

I recently removed the bolts securing the fuel injectors on an 87 Bertone. One of the heads sheared off. After removing the injector I had exposed bolt and attempted to work it out only to have it shear again. I am now looking at having to drill it out.

I imagine others have encountered this problem that seems unique (for me) to FIATs. Please offer your suggestions for (a) how I get the remainder of this bolt out without ruining the aluminium it has adhered itself to, and (b) what you do to get the old bolts and nuts on these cars to work as intended instead of rounding/shearing.

Thanks in advance.
Click to expand...

I'm late to this party but it was my understanding that FIAT used these alloys that would essentially chemically become "one"... so that Lock-Tite wouldn't be necessary...
 
You must log in or register to reply here.
Back
Top