help: how to remove snapped exhaust manifold stud

[L8apex32]

I'm in the middle of a DIY header install on a 1992 with 142k miles. Every single bolt or nut that has anything to do with the exhaust is heavily rusted. Some of the nuts have come off with Liquid Wrench + PB Blaster + 6-sided impact socket + either (arm strength + breaker bar | impact wrench).

I'd say 3 of the larger studs that connect the cats to the muffler have busted off. One of them I had to cut off. I have found that the bolts/nuts on the muffler side of the cats are more rusted, more stuck and less likely to come off that those on the manifold side of the cat - for what that's worth. No big deal as fastners, I think, will be easy to replace.

Of those little 10mm bolts that hold the cat shields on, most of them broke as soon as I put some muscle into my standard 3/8" drive wratchet. No big deal - small fastners like these will be easy to replace.

Ok, now, as I was removing the lower cat shield for the rear cat, I bumped the stock manifold area with it as I pulled it out. This felled a piece of metal that I didn't analyze right away. Turns out, lightly bumping one of the manifold studs broke the stud clean off. It was the one on the far end, to the driver's side, rear manifold.

I have since removed the other 6 nuts and the manifold with no further problems.

Question: How does one remove a sheared off manifold stud from the head? I haven't tried anything yet for fear of making this worse.

Any advice would be great.
Thanks.

 

[Larry Bastanza]

Typically I would drill out the center of the stud with a small bit that would allow an easy out to get in there if the stud is sheared flush. Then for aluminum heads I would use Propane to heat it until the stud turns out. I would heat the HEAD, not the stud the best I can. The aluminum will expand faster then the steel stud.

Obviously this assumes you can get a drill in there and can drill a STRAIGHT hole in the stud. You may need to remove the rear beam to be able to do this.

HTH,
LarryB

 

[drew]

After dealing with my 93 RX-7 for a few years: you become an expert at this process.

Larry has the most experience on this by far on the NSX, but I can probably add some additional pointers.

"Easy Out" is a tool and they work, but if they break off you are in a world of hurt. You have to drill even smaller holes around the Easy Out, extract that and start over again.

Another alternative to an Easy Out is a set of left hand drills. The LH drills do not get stuck, just progress up in size and eventually the stud should back out.

You may want to invest in a "close quarter drill" since there is so much riding on this repair. I bought a Milwaukee a long time ago and it is awesome, but you can buy Chinese crap for cheap (but you are on your own at that point).

After you are all done, you should get a tap and chase the threads on each hole.

Drew

 

[L8apex32]

The remaining stud sticks out about the manifold-flange's thickness. Would it make sense to try heating the head and turning it out with vice-grips?

Another suggestion I heard from a friend at work is to slot the bolt and use a screw driver to twist it out.

Any merit in trying these methods? I suppose that if they failed I could still do the EzOut afterwards.

If I choose to try the Ez Out, what size hole do I drill? Do I try one as big as possible without hitting threads or perhaps as small as possible?

Where can "close quarter drills" be purchased?

Thanks for the ideas.

 

[Larry Bastanza]

Larry has the most experience on this by far on the NSX

In all honesty, I don't.

Most of my experience in this area is with Porsche's, since this is a VERY common issue with them, and before I "converted" to the NSX, I worked on those for many years. For 911's I also had a pilot sleeve made for the drill bit, so it would keep the drill going straight into the center of the stud left in the head.

What I can say is using the method above has worked and saved my butt a few times.

I have never had a exhaust stud break on an NSX head, broke a few on the cats, but that is an easy fix, just knock them out and replace them.

Regards,
LarryB

 

[drew]

If you have a workable amount of stud, then go buy a Craftsman "stud remover". It works with your 3/8" ratchet.

Use quick snaps to loosen, rather than steady torque/pressure. In this case I would prefer a breaker bar to transfer the torque shock.

You should also tap the stud a bit with a hammer to break the chemical bond.

Personally, I am leery of Easy Outs because they can break off and then you will be screwed. Too small and it will break, too big and it can't get the bite it needs....so you gotta pick the right size.

I have also used a hammer with sharp punch to rotate the stud.

If all else fails you can hire a plasma bolt remover guy to come to your house and remove the stud. With my RX-7 I had him at my house a couple of times a year...that car was great fun to work on: you learned so MUCH.

 

[greenberet]

When I removed my old headers this winter to put some new ones on, two of the studs from the rear bank of cylinders sheared off at the point where the rusted nut was. The studs didn't shear off flush with the cylinder head and there was enough sticking out that a "stud remover" removed both pretty easily.

 

[Larry Bastanza]

When I removed my old headers this winter to put some new ones on, two of the studs from the rear bank of cylinders sheared off at the point where the rusted nut was. The studs didn't shear off flush with the cylinder head and there was enough sticking out that a "stud remover" removed both pretty easily.

Now that would be really great if you have a stub left to grab. I have a set of these stud remover's you mention and they do work very well.

Regards,
LarryB

 

[L8apex32]

When you say "set of stud removers" does that mean you are talking about the ones that look like sockets, but have vertical teeth on the inside? You hammer them over the stud to get a good grip, then use a socket over them to turn them out? I saw those when looking at Sears's website.

Would I use them while heating the head also?

There is also a singular "stud remover" which fits over the stud and grabs it by the side. http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&pid=00904458000&cat=Mechanics+Tools&subcat=Socket+Accessories&vertical=TOOL&ihtoken=1
I'm not sure there is room enough for this one.

Which one were you describing, greenberet?

 

[greenberet]

I used a stud remover that looks like a socket for a socket wrench and has three cams inside arranged concentrically around the middle, where you stick the stud in, that come "on cam" as you turn it and that thereby grip the stud. It looks pretty much like this one with a slightly different mechanism inside. When looking for a stud remover, I saw there are various designs. The one I bought wasn't supposed to damage the threads of the studs to be extracted or installed, it grips low down on the stud so that not much needs to be sticking out for it to work, and since it has the 3/8" drive on the same axis as the broken stud, you'll get accurate readings with a torque wrench.

However, the cams inside do damage the threads, as I found out when I wanted to remove the studs from an old motorcycle crankcase. So you wouldn't want to use it to install new studs and therefore it also doesn't matter that you get accurate torque wrench readings.

The stud remover you posted a link to looks like it'll do the job well, as long as there's enough of the stud still sticking out for it to grip. Stud pullers with vertical teeth would probably also work just as well as long as you have the right sizes.

To install the new studs, the best way I found is to buy a cap nut that you can screw onto the studs, and a ball bearing you can drop into the nut before you screw it onto the stud. You won't damage the threads at all when screwing the stud into the cylinder head and once it's in, you can unscrew the nut without it pulling the stud out again thanks to the ball bearing.

 

[Zennsx]

Is there any possibility of double nutting the stud in question?

 

[L8apex32]

I was unable to find a stud remover from Sears (although there are 3 or 4 listed on their web site - none were in their computers or on the shelf) and the specialty tool places were closed by 6pm. The two auto parts stores we checked don't have them.

The good news is that I when I took another look, with vice grips and blow torch in hand... I saw that there is 3/4" sticking out. This should be plenty of length for several of the stud remover type devices to work. There is room around it, too, to use hand tools.

I sprayed on more PB blaster and checked how much grip vice grips can get: not that much on threads wet with PB Blaster. I probably munged the top 1/2 of the threads... maybe I can double nut it, maybe not. I can buy a metric tap/die set and chase the threads which may allow me to double nut it.

I am thinking that a stud remover is going to be my best option... I just need to find one for sale here in KC.

So far, the summary take-away for others doing this project is that it seems that if a manifold stud breaks on disassembly, it will leave a good chunk of the shaft out and available for gripping/pulling/etc. The flange on the stock manifold is actually very think which makes this possible.

Assuming I find a stud remover, should I bother with heating the head first... to make it easier to come on out? Or, should perhaps a few taps with a hammer be enough, then just use the tool without heat?

Thanks again for the advice.

 

[Larry Bastanza]

If you cannot find the stud remover and you have a good size vise grip, you can take a small dremel grinder and put flats on the broken stud. Then grip that baby with a vise grip as tight as you can get it, even tighter.

Apply heat to the head area and the stud will back out. These studs are actually not in very tight, it should come out perfectly clean. I suspect you can just thread in a new one, remember you have not damaged the threads in the head at all, they should be clean.

Interestingly, when I have a jammed nut on an NSX exhaust, usually I end up with the nut and stud in my hand. Then I double nut the stud to remove the original small castle nut.

HTH,
LarryB

 

[L8apex32]

A stud remover worked perfectly. The stud wasn't even in there that tight. Thanks for all the suggestions.

Next question: how to remove studs from cats. These studs have a flat head on one side - I assume I pound them out. Is the process:
o use PB Blaster
o heat cat flange
o pound with hammer
o heat more
o repeat

I had to cut two of the studs off... I'll need something like a punch to pound it out. Any suggestions on this?

Thanks.

 

[greenberet]

I didn't want to pound on the catalytic converters with a hammer because I was afraid something would break inside. I took them to my local Honda dealer and they drilled out the bolts for me.

It was such a pain removing the exhaust system with all those rusted bolts and nuts that I never wanted to have to deal with it again. I replaced every screw, bolt, washer, and nut in the entire exhaust system except for the cylinder head studs with stainless steel hardware meeting the German A4-80 specification, which supposedly will not rust even if subject to acids and high temperatures.

 

[L8apex32]

I'm sorta on the same mission. If I find a reasonable way to get these studs out of the cats, then all of the studs will be replaced with stainless bolts.

As far as drilling out the studs, that seems like a fairly easy do-it-yourself project once the cats are off the car. No worries if you don't go perfectly straight, right? Even if the hole is not perfectly straight or if it gets a little oblong, won't the new bolts holt it tight anyway?

What is the best way to drill out a stud - as far as in drill bit sizes? Is it best to start small, then work your way up? Or, is it better to just go with the size you need right off the bat?

 

[L8apex32]

Last night I tried removing the studs in my cats by pounding them. I started by setting the cat on the ground and hitting the studs with a good sized hammer. My aim was so-so and after a few good smacks... nothing.

Then I got out the sledge. I can't remember if its a 10# or a 16# sledge but its a big over-the-shoulder one I purchased to remove a small concrete patio. My best smack was when I had my wife hold the cat on the concrete driveway and also have it supported laterally by wood blocks. I nailed it with the sledge... nothing.

I spent another 40 minutes using new drill bits... which take FOREVER to drill though the 3/8" of stud. This was NOT going to work.

This morning I took the cats to the Acura dealer. The service writer sent me to the parts desk and I showed the parts guy my cats and said I need those studs out. He said, hmm, let me check. 4 minutes later, he comes back and the studs were gone. He did the same for my other cat.

They used an air hammer. I didn't get to watch... but it worked so perfectly. After all my frustration and using about every tool I had... they got them out in 10 minutes.

Count one big "good job" and "thanks" to Superior Acura in Kansas City.

 

[AR]

I just ground off the base of the studs, got the flange rested on a metal lip ( anvil type surface ) and hammer them out.

After that I passed emissions with those cats.

Cheers,

AR