Screw extraction advice

[Stevehose]

I'm working on a friend's Tii and I went to reinstall the Kfish belt cover and noticed one of the bolts had it's head snapped off back in the day, which explains why there was a missing bolt when I removed the cover. It's the typical M6 bolt, similar place as the waterpump ones, which means back breaking location. Any advice on how to extract this puppy? I've never had too much success with this operation. Any good devices out there? My right angle Dremel drill just arrived, perhaps this could be used.

 

[adawil2002]

Spray with penetrating oil like 3-in-1 or CRC. May need to remove the grills to get a decent angle. If you are able, cut a slot in the bolt to unscrew with a screwdriver. Have had mixed results with drilling & extracting bits.

 

[Stevehose]

Soaking in Liquid Wrench since discovery. I like the slot idea thanks

 

[Bimmer 3.0 CS]

Had good results with AeroKroil penetrating oil

 

[Markos]

Think of it this way. If you snapped the head you will likely snap a screw extractor. You will be working with a 3mm screw extractor at-best. The torque to move it will snap the extractor. Then you will have a hardened steel extractor tip in the way.

Is that bracket aluminum? You may have a dissimilar metals situation. Agreed that you should soak it in penetrating fluid. The thing about aluminum is that it expands much faster than steel. If it is aluminum, you can use the screw extractor, the fluid, and a torch. Hit the aluminum from the side. Get it nice and hot. Then insert the extractor. If it doesn’t want to move, repeat.

BTW - You can use the same method of heating aluminum to drop/pull steel bearing races from an aluminum housing (transmissions, transfer cases, differentials, etc.)

 

[m5bb]

I just broke a screw extractor on Sunday trying to remove an 8mm bolt from a 2002tii strut tower. The three bolts at the bottom like the E9 with holes for safety wiring. They had never been removed in 48 years.
Screw extractors are not easy. First the hole you drill in the bolt to use the screw extractor must be centered to work well. A center punch is needed to provide a place for the drill bit. Not easy to get in the middle.
I have done this before and it worked but this time it did not.
Had to take to a machinist to drill out the broken screw extractor (easyout) Takes carbide drill to drill out the extractor because it is special steel.
Markos suggested the heating idea and I agree completely on that. I would go one step further and heat it up and then take a compressed air can like you use to clean a keyboard. Turn it upside down and use the cold Freon to cool the area. Do this a number of times all the time applying your favorite penetrating fluid. This expands and contracts the area around the bolt and hopefully breaks that aluminum to steel chemical bond.
A trick I know that has much success it to weld the same size bolt to the one that is broken off. Then you can turn that bolt to remove the broken one.
I this case the bolt is small and probably not a very easy area to get to. The slot and screw driver will probably be the only simple way.
Patience is the best here. Take your time.

 

[Markos]

Great advice @m5bb. I’ve never tried the heating and cooling technique. I will have to remember that one. My advice was based on experience also. I lived in states that use rock salt and mag chloride on the roads. Stuck bolts is a common phenomenon. I am still amazed at how easy fasteners can be removed on Washington cars.

Gary relays the same experience that I have had. I have broken countless screw extractors. If the bracket is aluminum then you have a great advantage. A propane torch is sufficient, preferably with a small torch end to keep that k-fish belt safe. Better yet, remove the belt. If you need to leave it in place, you can buy a little black pad that protects the belt from the flames. They sell them at home depot and plumbing stores. I use them to keep my floor joists from burning when soldering copper pipe.

The welding a nut trick works well. I didn’t suggest it because that is a big leap from drilling and heat. I’ve only had to do that once. I snapped the bolt off the first time, and had to use another bolt. It can be tricky to get good penetrationIf you go that route try to use a blackened bolt instead of a zinc bolt. It’s a split second of welding but Zinc fumes are toxic.

 

[Sharkie]

Sounds like you have lots of good advice from these members, in my experience the heating and cooling will work well, however you must understand the aluminum's melting point. Its unlikely a propane torch will cause damage but just be aware. the heat / cool cycle should break the bond. one other piece of advice, and this is gonna sound weird but you need to have a positive attitude and tell yourself your going to win. I know this sounds odd but it really works for me. Cheers and take care, stay healthy!!

 

[Willem Tell]

Penetrating oil, heat and cooling sounds like a plan. It might be obvious, but since nobody has mentioned this, when you do try to drill the bolt for the extractor, use a left-hand twist drill. That way any torque introduced when and if the drill bites, it's turning the bolt in the right direction (out).

 

[Sooner]

Strongly suggest Open and Shut penetrating product!

 

[Stevehose]

It is aluminum. Patience is the key from what I read above. I saw online where it’s drilled then a torx bit is hammered in, a twist on Andrew’s suggestion. That’s plan A. I’ll heat and cool it a few times before any twisting. Thanks I’m going in

 

[HB Chris]

Like Gary, I had a bolt snap in the bottom of the strut due to my own ignorance. We cut a slot with a Dremel for a large screwdriver, and put a wrench on the driver’s shaft and got it out.

 

[bluecoupe30!]

I snapped one of the 4 bolts that secure the water pump to an E39 block once. Welded a bolt to it and it backed right out. Good luck Steve.

 

[day66]

I've found the "weld on a nut" trick works much better if you weld a washer onto the remains of the bolt before adding a nut on top. Pick a fairly thick and wide washer the right size for the broken bolt and puddle the middle with weld. Then weld the outside of the nut to the washer and puddle weld into the middle. You'll end up with a glowing orange bolt and this means there's a lot more heat to break the rust bond - and the washer stops the nut gouging into the surrounding metal.

 

[deQuincey]

I'm working on a friend's Tii and I went to reinstall the Kfish belt cover and noticed one of the bolts had it's head snapped off back in the day, which explains why there was a missing bolt when I removed the cover. It's the typical M6 bolt, similar place as the waterpump ones, which means back breaking location. Any advice on how to extract this puppy? I've never had too much success with this operation. Any good devices out there? My right angle Dremel drill just arrived, perhaps this could be used.

if it is an M6 on aluminium i would use the bolt extractor without a moment of hessitation, but my experience says that it is key to make the hole as big as possible, so obviously you have to make a great effort to center the first hole,
as to tools i use a spring loaded centering punch, easy to use when there is lack of access

if it is an M6 you can use safely up to 5mm drill bits, this will give also the chance to heat up the bolt internally (i would be careful to use a torch if there are sensitive parts around)
drill in small increments, but start with 3mm, never less than that as there is also the risk of breaking a drill bit inside the bolt and that is not good
if you are drilling the bolt HSS drillbits are good, cobalt ones preferred but not mandatory (cobalt is a must over forged iron like the engine block)
check the depth of the existing hole and limit your advance to that one

as to a flat slot i see the difficulty to be able to make a slot profound enough without damaging the walls, if the slot is not deep enough its walls will break easily, the good news is that broken walls do not mean additional hardened material inside like in the extractor or drill bit cases
good luck

 

[deQuincey]

I've found the "weld on a nut" trick works much better if you weld a washer onto the remains of the bolt before adding a nut on top. Pick a fairly thick and wide washer the right size for the broken bolt and puddle the middle with weld. Then weld the outside of the nut to the washer and puddle weld into the middle. You'll end up with a glowing orange bolt and this means there's a lot more heat to break the rust bond - and the washer stops the nut gouging into the surrounding metal.

but this time the base is aluminium...would you dare to use welding on it ?

 

[Markos]

That is fantastic advice!

I've found the "weld on a nut" trick works much better if you weld a washer onto the remains of the bolt before adding a nut on top. Pick a fairly thick and wide washer the right size for the broken bolt and puddle the middle with weld. Then weld the outside of the nut to the washer and puddle weld into the middle. You'll end up with a glowing orange bolt and this means there's a lot more heat to break the rust bond - and the washer stops the nut gouging into the surrounding metal.

Also great advice! Fortunately steve tackles a lot of complex technical tasks that others may be worried to take on. Like rebuilding steering boxes and stuff.

one other piece of advice, and this is gonna sound weird but you need to have a positive attitude and tell yourself your going to win. I know this sounds odd but it really works for me. Cheers and take care, stay healthy!!

 

[Markos]

but this time the base is aluminium...would you dare to use welding on it ?

I was thinking that the puddle could melt the bracket if it spills over. I really don’t see this extraction being a problem. Good call on the hole size. The bigger the extractor the less likely it will snap.

If you have to slot the bolt, you will need to slot the bracket also. That is a cosmetic problem. If you resort to that, I would do the welded washer/nut first. I don’t think it will come to that.

 

[stphers]

From what I see and knowing where this broken bolt is and that it is broken off just below the surface of the timing cover, I think that the only way that you are going to fix this is by drilling it out So really frigging important to center punch the broken bolt in the center, start by using a small drill, working up to a drill bit that is a 5mm , then use an easy out Heating it up a number of times may cause it to actually seize in there even more Once or twice will be ok I know this because I deal with broken bolts almost everyday as I all I do is work on late 60's and early 70's German and Italian cars

Take your time and it will come out, worse case, you may have to drill it right out and helicoil the hole

Good luck

Thanks, Rick

 

[Markos]

I wouldn’t trust myself to hand drill it out to 5mm. Correct me if I am wrong but 6mm is the other “major” diameter. That doesn’t leave you much margin of error. 4mm, sure.

@Stevehose,

If you have to go to the hardware store, get an M6 x 1.5 tap (I presume it is 1.5). You can use it to chase the threads when you are done. If you do get sideways you will eat into the bracket like butter. Retapping are the original size though might make it salvageable.

I bought a giant metric tap and die kit from HF. It is pretty exhaustive but doesn’t cover the whole car. For instance, I had to buy a separate M16x1.0 die for the threaded wiper shaft. Weird size, bolts that diameter are usually coarse.