Removing a broken exhaust stud

[captmello]

Hi Guys, I'm doing some repair work on my bobcat. It has a small kabota 3 cyl diesel. I found it has a broken exhaust manifold stud at the rear of the engine. It is not too difficult to get to, but space is limited. I have no experience removing old studs but I do have a few ideas of my own. The manifold is removed. The stud sticks out from the head about 3/16 of an inch and is about 1/4 inch in diameter.

My first inclination is to grind a slot in the end of the stud and try to unscrew it. I think i can fit my dremel in there to cut the slot. I'm wondering if i should heat the area around the stud before trying to unscrew it since I feel like I only have one chance and will either break it or get it to turn out. the other option would be to try to drill a hole in the stud and use an "easy out" extractor type tool to try to get it to unscrew.

Any advice is appreciated.

 

[alldodge]

You do want heat, and the more the better. Get it hot and then put some candle wax on it.
If you can grab the end with some vise grips or something similar try it.
A welder is real handy for this. Take a washer and weld the washer over the stud, then weld a nut to the washer. All the welding heats its up good and it will unscrew. Used this same method removing a couple studs on my loader exhaust

 

[Scott Danforth]

welding a nut onto the nub works 90% of the time.

I prefer to use a 50/50 mix of ATF and anti-freeze, or Kroil. PB blaster works about half of the time

weld on the nut, wait a minute, douse with the ATF/Acetone. wait about 2 minutes prior to adding heat again. re-heat with a torch, douse again, then simply back off the bolt.

the other 10% of the time involve colorful language, a center punch and a pile of drill bits and sometimes a helicoil

 

[captmello]

Thanks for the responses! I have heard of the method of welding on the nut but I do not have the equipment to do it. No one likes the slot in the end idea? AD, I could probably get a vice grip on it but all the other studs will be in the way of turning it. the area isn't really rusty, all the other nuts screwed right off the other studs, I just figured the heat would soften any locktite type materials that may have been used to keep the studs in tight. I'm going to soak it with PB for now and probably attack it this weekend.

Thanks again!

 

[bigdee]

Welded nut like Scott described is my first choice. 2nd would be the ezy-out....preferably drilled with a left hand bit. More likely to screw up with 2nd method but if you do you can always re-tap or use a heli-coil.

 

[alldodge]

Don't see you getting enough force being applied with a slot a screw driver. You could give it a go, the worst that could happen is it didn't work.

If you have a small pipe wrench (6 inch or so) could try grabbing it.

There should be no locktite on it, its just heat and rust causing the issue. Use a propane torch and het it up some, then hit it a few times with a hammer. The hits might cause the rust to weaken. Don't hit it so hard you mushroom what's left of the stud

 

[bigdee]

There should be no locktite on it,

Yes there is NO lock-tite on exhaust studs.....locktite is not for heat use above 300ᴼ....it melts.

 

[captmello]

So I did some head scratching last night while doing my workout, curling 12oz cans...I thought of all the tools I have, being a remodeling contractor, and one tool I don't have because I hate the sound they make, is an impact driver. So, I thought, why not, I have an 18v bosch drill, I'll add a driver and see what happens. They did not have any flathead impact rated bits, so I bought a couple regular ones. Initially I had trouble keeping the bit in the groove I had cut in the stud and eventually kinda tore up the groove, and I realized that the bit was bending. I still had some meat on the stud so I cut the groove deeper and thought some more. It occurred to me that I have one of those semi-useless impact screwdrivers that you hold and hit with a hammer. It came with some oversized bits. Well, I couldn't get a good whack on that at all, but...I had adapters to convert my new 18v impact driver to hold the oversized flathead screwdriver bit that came with the now fully useless impact screwdriver. Well that did it! No heat, no welding, no four letter words, just success.

thanks again to all that chimed in. I'm just waiting on my bobcat parts now.

 

[alldodge]

Cool, great to hear

I just bought one of those impact drivers and while I don't care for the noise either, I love the thing. Just built new steps and used the star bits and also some regular Philips, and not one screw rounded off.

 

[Brandon5778]

Hey guys, question on this subject. I've heard of the welding a nut method before, but what if the bolt you need to get out is broke off inside or flush with the head like is the case on my Chevy 6.0? Is the only option cursing and drilling?

 

[alldodge]

Hey guys, question on this subject. I've heard of the welding a nut method before, but what if the bolt you need to get out is broke off inside or flush with the head like is the case on my Chevy 6.0? Is the only option cursing and drilling?

No, use the same method, you weld a washer on it first. Welding the washer will bond to the stud, but will not bond to the cast iron. Then weld the nut to the washer and it will come out. Used this method a few times on heavy equipment

 

[Brandon5778]

No, use the same method, you weld a washer on it first. Welding the washer will bond to the stud, but will not bond to the cast iron. Then weld the nut to the washer and it will come out. Used this method a few times on heavy equipment

Thanks AllDodge. I just can't wrap my head around how it would work if it is broke off deep. I have 2 broken exhaust manifold bolts on my truck, and they are both broken about 1/4 inch deep inside the threads. I mean, a washer over it wouldn't contact it. Unless I'm missing something, which I probably am.

 

[alldodge]

It works but have not tried that deep, slightly below but not 1/4 inch. It is very hard to weld cast iron, so in removing a stud that is a good thing. Find a welder and ask them or try your question in link below, very knowledgeable folks. Mine was done on heavy equipment forum

http://weldingweb.com/

 

[Scott Danforth]

if your broken off that deep, you can only drill unless its an aluminum head

 

[Boomyal]

Captmello, be sure to check the manifold for flatness. Some times manifold warpage is the cause of studs snapping. Often when that is the case I have seen the remnants of the stud back out with little effort. If the manifold surface is not totally true, have it machined.

 

[jakedaawg]

I can do them 1/4 " or more below deck height. I use tig and a gas lense and extend the electrode way out. A little tinfoil to make an argon dam. 70 S 2 wire for fill. .040 works well. I just build it up till I can fuse to the washer. Probably done 15 of those darn 6 liter Chevys this way. Most common issue with that motor is the rotten exhaust setup

 

[Brandon5778]

I can do them 1/4 " or more below deck height. I use tig and a gas lense and extend the electrode way out. A little tinfoil to make an argon dam. 70 S 2 wire for fill. .040 works well. I just build it up till I can fuse to the washer. Probably done 15 of those darn 6 liter Chevys this way. Most common issue with that motor is the rotten exhaust setup

That's exactly what I was looking for. Thanks, Jake. Yes, I've heard almost every one of those old 6.0s had this problem.