Broken studs

[CalebD]

I once tried to take off the water jacket on my A4 and the first bolt I worked with broke the stud. Needless to say I walked away from that job although I would still like to be able to do it sometime soon. Another A4 owner at my boat club (Lee and her Pearson 30') also has a similar problem.
So, my questions are: What is the best way to deal with a broken stud in the engine block/head/manifold etc? Does the MM manual have a description of how to deal with this? Keep in mind that both of these engines are in tight engine compartments and not so easy to work on.
Thanks for any advice in advance.

[marthur]

There are two or three ways to deal with a broken stud.

First is the "easy out" tool: I personally have had terrible luck with the "easy out". I don't recommend it. When it breaks you will have a much bigger problem than when you started.

Second, drill out the old stud: Center punch the broken stud. Using the newest sharpest drills you can buy, start small and drill successively larger holes until you are just about drilling the threads of the hole. Pick out the old threads or clean out the hold with a tap.

Third, remove the head and use a stud remover or vice grips on the stump to remove the stud.

Good luck!

[hd78half]

I concur with Marthur. If the stud breaks, then the Easy-out probably won't budge it.

If you can get a stud extractor on the remaining exposed portion, give it a try. There's a good chance though that it will snap the stud off.

Marthur's option #2, drill it out and re-tap is typically the route you'll end up with. With good, hard drill bits this is not hard or time consuming. The trick is to make certain the center punch and the first drill bit start on the center of the stud.

Break a leg
Al

[Dan F.]

I get to do lots of this in my day job. Drilling and easy outs are great! I tell my apprentices to do it in steps.
1st -Penetrating oil and heat
Put on a good penetrating oil. Everybody has their favorite.Some work better than others. After 25 years of rebuilding aircraft engines that have been through some nasty tropical service I would put my money on ACF-50. Talk to your local aircraft mechanic.It is easy to get and inexpensive.

Put on the oil and apply localized heat. The heat makes the metal expand and capillary action takes over. A torch works best, or if it is risky, just use a hairdryer.If you know you are taking off your exhaust manifold, apply the oil and go for a cruise. A little prior planning helps heaps.

2nd - Vibration
I think you have to break a few before this will make sense. Before a stud breaks it starts to feel different. If it is wet it will smoke a little bit sometimes as the work hardening process progresses heat is generated and you make the metal more brittle. The trick is not to get to the work hardening phase. The stud will have a little springy feeling .( sorry I am not a writer.) Once past the yield point it is game over.

If it still doesn't come with the oil heat and brute (almost destructive) force,apply more oil and vibration. You can put a nut on it and tap it with a hammer. My preference is a rivet gun with a brass snap if you have access.(regulated down) It is just quicker.

3rd- Wiggle
No.Not your rear end. Well if it has already come out, DO IT!
Maybe the stud moves a wee bit then gets tight again. If you tighten it up and loosen and tighten.....wiggle it with more oil and heat.Capillary action comes into play, and more oil gets in there.

4rth- Plan your attack
Right now the thing is still in tact.Sometimes a wait overnight with more oil on it helps.Is breaking it going to help or hinder. Each situation is different.If you have time, more oil and try tomorrow. If not,go for broke and plug on, or get professional help. At this point it is inexpensive. Break the easyout, crack the hole, or damaging the part will cost you more in machining charges, or even scrap the part!

5 -Go ahead and break it!
It will feel good too, if it was by choice. Trust me! A stud will usually break close to the surface or level with it.It is rare it will go in 2 or 3 threads.
With accessibility set aside you now have 2 options.
Weld a nut on it and go again.
Pound on a stud extractor. Gibsons Aircraft sell stud extractors that just pound on to a broken stud. There are teeth on the I.D. You can then wiggle away.

If this still fails bust her off again. Since it is a choice it will feel good! Kind of. You will now have a fresh break, and at this point it will be fairly flush to the surface.This is the scary part everybody tells me about.

6. Drill and easy out

Now you center punch it and drill it. Use a small drill bit at first for 2 reasons.
If you are off center a bit it won't matter. You can correct it with the next try. If the bit is too large, it will try to "walk" easier than a small bit. Whoops!
Right across a machined flange like your thermostat housing for example.
Now you have 2 problems!

Drill it straight (have a spotter eyeball the drill for you) and drill it through the stud. There is always space at the bottom of the hole. If you drill it crooked you will not transmit the torque at 90 degrees to the stud. This is where easy outs become uneasy to take out.You help to shear them off!

Easy out kits come with drill bits sometimes and always I have found them to be too small. Essentially you want to drill out the center of the stud to relieve some of the pressure holding it in there, but not too much that the easyout will just swedge it in there more or worse yet, crack the hole! I am sorry, but I cannot put this to words.One, maybe two sizes bigger is better here.I will get a digital picture and insert it at a later date.

Gently tap the easyout into the hole and try it. Some guys pound it in there to get a "good" grip! They end up putting more sideloading on the threads to hold it in there better.(the whole reason for drilling it out) Don't mangle the hole too bad.STOP if the extractor starts to work itself into the hole like a screw!!!

If this STILL doesn't work , break something. It will feel good....trust me! Do not break the easyout! Live to fight some more. Most guys crank on this figuring it is your last hope.

7 Drill and helicoil.

By not breaking off the easy out ( I can get them out there is two ways we won't go there) you still have two options. With the hole still relatively round, you can drill it and use a tap to clean out the threads. It may or may not work. Maybe the thing picked up in there and there is no saving her.(I don't bother. Being paid to do this it is not cost effective for the customer. I just go to the helicoil phase. You do not yet own a helicoil kit so yo might want to save the 18 bucks. It is all about choices and economics.)

Helicoil it. With a helicoil kit you use a specified sized drill , tap it, insert a stainless coil in there ,break off the inserting tab, and you are back in business with a structurally stronger hole! But wait.... I used the wrong drill bit and the hole is too big to accept threads!

8 Twinsert
Guess what? You can STILL fix it! Twinserts. It is the same as helicoiling it. You go up another size, put in a coil, and then put in a coil to match your stud diameter. You bugger this up, and you can still fix it. Now I would be going too far.There are another 2 ways I could put to make it an even 10.Expensive machines are required so we won't proceed.

My point here is simple.Baby steps. There is actually many windows of opportunity to get the offending fastener out and salvage the part.Accessibility aside, it is a progression. Each step has a couple of alternatives if it fails.

Going from step one to step 6 closes many doors! Most use step 1 and step 6
and end up wary of stuck fasteners or doing more harm to it to prevent removal.

Good luck on your next stuck fastener!

Regards,

Dan