How to remove broken exhaust stud

[coreydmc]

Hi everyone

I needed to replace the exhaust manifold gasket because it just started leaking. I bought the gasket kit for the manifolds, cat, and crossover pipe . Also a new 02 sensor. I was almost successful in removing all the exhaust manifolds studs but one broke on the drivers side. It was the lower one closer to the head gasket. It still has about 1/2” of it showing. So I guess I’m lucky it didn’t break off flush. Can I use a MAP gas torch to heat the stud and try and remove with vise grips? I don’t want to overheat the aluminum head and warp the head gasket. I wanted to try heat first because I have the map gas and a regular torch. If that doesn’t work I’ll get a welder and try and weld on a bolt to the remaining stud and try and unscrew that way. I just needed thoughts on the map or torch heat with aluminum head....
Thanks in advance!

[DMC-81]

Hi everyone

I needed to replace the exhaust manifold gasket because it just started leaking. I bought the gasket kit for the manifolds, cat, and crossover pipe . Also a new 02 sensor. I was almost successful in removing all the exhaust manifolds studs but one broke on the drivers side. It was the lower one closer to the head gasket. It still has about 1/2” of it showing. So I guess I’m lucky it didn’t break off flush. Can I use a MAP gas torch to heat the stud and try and remove with vise grips? I don’t want to overheat the aluminum head and warp the head gasket. I wanted to try heat first because I have the map gas and a regular torch. If that doesn’t work I’ll get a welder and try and weld on a bolt to the remaining stud and try and unscrew that way. I just needed thoughts on the map or torch heat with aluminum head....
Thanks in advance!

If there are still threads showing, you can try this technique in post 16 of this thread:

http://dmctalk.org/showthread.php?14704-Refurbishing-stock-exhaust/page2

[coreydmc]

All the exhaust stud threads in my drivers side head are completely stripped out. I do have the 7mm studs from DMCH but I will need to drill the heads and use a heli-coil. I was wondering if it was possible to just use a SAE stud from NAPA or even a ACE hardware? I figured if I can use a slightly bigger SAE size than the original 7mm I could get away from using the heli-coil and I could just tap the stripped hole for the SAE size stud. Does that make sense and is this possible?

Also some of the stud holes are close to the edge of the head. Is there enough room to use a heli-coil if I need to?

I’m thinking of getting new exhaust manifolds since my are pitted and they are off the car. Is this strictly a Delorean part or were these the same for a early 80’s Volvo? I’m thinking not because I’m not sure the Volvo had the crossover pipe.

Thank you for your help

[David T]

The only repair that will last is to use the Heli-Coils or other brand of thread insert. As for the manifolds, Eastwood.com sells stuff that can make them look like new.

[David T]

MAP gas doesn't get it hot enough. An Oxy-Acetalyne torch will do it. Heat it up to cherry red, let it cool, heat it again and then remove it, along the threads, from the head. Then Heli-coil it. Use plenty of Never Seize when you put it back together.

[coreydmc]

Sounds good! I will buy a pair of exhaust manifolds from someplace. I’ll call Rob Grady tomorrow and see if he has the 7mm heli-coil kit and headers. Has anyone been successful in doing the complete drivers side with the engine still in the car? I have a lift so I hope it will make it easier. I’m just worried about clearance issues with the engine in the car.

[mluder]

Couple of things...
Do not use WD-40. Use a proper penetrating oil like Liquid Wrench, PB Blaster (my preference), etc.
A MAP torch will work just fine... at least it did for me.
I heated the stud until it was red hot, turned off the torch, and then sprayed it with the PB Blaster. The heat seems to draw the lubricant into the threads. I did this several times allowing over the course of a couple of days.
Because mine broke of flush, I used a center punch to set a start. Then I used left handed (reverse thread) drill bits starting small and working up. Then a finally screw extractor.

Because you have threads showing, a pair of vice grips should do the trick.

Cheers
Steve

[Rich_NYS]

Couple of things...
Do not use WD-40. Use a proper penetrating oil like Liquid Wrench, PB Blaster (my preference), etc.
A MAP torch will work just fine... at least it did for me.
I heated the stud until it was red hot, turned off the torch, and then sprayed it with the PB Blaster. The heat seems to draw the lubricant into the threads. I did this several times allowing over the course of a couple of days.
Because mine broke of flush, I used a center punch to set a start. Then I used left handed (reverse thread) drill bits starting small and working up. Then a finally screw extractor.

Because you have threads showing, a pair of vice grips should do the trick.

Cheers
Steve

+1

I used very similar techniques:

I used a MAP torch to heat the studs and first use a spray bottle with water (for rapid contraction) to "crack it loose." I follow that with heating the stud & spraying penetrating fluid while hot (to draw it in,) but not so hot it sizzles away in a puff of smoke. I don't know for sure, but I believe most of the penetrating fluid "vaporizes" if the stud is too hot.

Andrew told me about acetone + dexron, so I read a study that tested it against well-known penetrating sprays....it beat them all (WD-40 ranked horribly.) In addition to the above, I soaked the studs everyday for 2 weeks with acetone/dexron mixture.


For a broken-off stud, I'll share this method for entertainment purposes only:

The guy who runs an import shop in my area uses an arc welder to weld a bolt onto a broken stud, then removes it with a regular socket. He uses the bolt as a welding rod, and zaps it onto the end of the broken stud. He said they come out pretty easily because when the stud breaks on removal, it's usually "cracked loose" and comes right out.

-I'll take a pass on trying that one -lol!

[coreydmc]

Stud came out. Ordered some M7 10mm and 14mm length Time-Sert coils. I need to tap all the studs
on the driver side. Hoping I can drill all the studs on the driver side to install the time-serts with the motor still in the car. I found a set of headers on Delorean Industries for $395. Anyone know of a cheaper place?

[David T]

The "welding" trick works. The way I do it (mainly for large broken off studs or bolts) is to place a washer on the surface, weld to the broken off stump, come up above the surface and then place a nut on the washer and weld the whole mess together. Seems to work best if you stick weld. The slag keeps you from welding the hole up. Let it cool and it screws right out. I have done it many times on cast iron. Not so much on aluminum but it should work, it's just that on small stuff it is difficult to get in there. For small bolts heat is all you need and small stuff is easy to drill out. if you still have the stump sticking above the surface you don't usually have to drill except to install the threaded insert. On aluminum, most of the time you wind up ripping the threads out. This is why, when removing steel fasteners from aluminum, (especially exhaust hardware!) I always heat them up before even trying to remove them, saves the threads. The heat breaks the corrosion. When reassembling always use Never Seize so the parts can be undone easily. For the exhaust studs PJ Grady has the best hardware, it's stainless and will never corrode but it is pricey.

Drilling is only part of the problem. I found it difficult to get the tap perpendicular to the surface. Be really careful about that and go slowly till you are sure you got it right. Use plenty of cutting fluid and back up after 1/2-1 turn to clear the chips.

[JETS 81 DMC]

Just to add an old school method of a stuck fastener I had heard of years ago.

Heat up the fastener and take a candle and melt it around the hot threads.

It does work. You can google it too.

The acetone mixture that Rich mentioned I had read the same article and that also works.

WD-40 is useless in these cases.

[DMC-81]

Just to add an old school method of a stuck fastener I had heard of years ago.

Heat up the fastener and take a candle and melt it around the hot threads.

It does work. You can google it too.

The acetone mixture that Rich mentioned I had read the same article and that also works.

WD-40 is useless in these cases.

Yeah, that candle trick is the method I linked to in my exhaust refurb thread above. It worked well. And yes, WD-40 is more of a lubricant rather than a penetrating fluid. WD-40 works for me, but definitely, one can evaluate the level of the rust they are dealing with and use their favorite penetrating product. :wrenchin:

Coreydmc, I'm glad you got them out. That's a tedious task for sure.

[coreydmc]

Here is a crazy question. On the manifold head studs which length goes into the head the shorter or longer? The ones I have from DMCH are 10mm threads on the short side, 18mm long side and 10mm smooth no threads in the middle. I thought the short side goes in the head, but 10mm doesn’t seem like enough bite...

[DMC-81]

Here is a crazy question. On the manifold head studs which length goes into the head the shorter or longer? The ones I have from DMCH are 10mm threads on the short side, 18mm long side and 10mm smooth no threads in the middle. I thought the short side goes in the head, but 10mm doesn’t seem like enough bite...

I installed the shorter (10mm) side in the head:

http://dmctalk.org/attachment.php?attachmentid=49073&d=1487555772

[coreydmc]

I installed the shorter (10mm) side in the head:

http://dmctalk.org/attachment.php?attachmentid=49073&d=1487555772

Did you use any sealant on the studs going into the head?

[David T]

Never Seize. Use liberally on all of the exhaust hardware but be careful, it can get messy.

[coreydmc]

Thanks Dave! I forgot to ask should I use RTV on the exhaust manifold gaskets or leave dry? If I use sealant is it on both sides?

[DMC-81]

Thanks Dave! I forgot to ask should I use RTV on the exhaust manifold gaskets or leave dry? If I use sealant is it on both sides?

Hi. No sealant on the studs, but like David said, Never Sieze.... but I would caution you to not apply too much. Otherwise you'll increase the risk of the studs backing out under vibration. I recently had that happen after a few months on my daily driver engine rebuild. What a pain to retighten them in the car:

http://dmctalk.org/attachment.php?attachmentid=55305&d=1518315545

I used high temperature RTV (red colored) on the gaskets, both sides, as shown. If you want more detail, I outlined that in the thread I linked to above.

http://dmctalk.org/attachment.php?attachmentid=49022&d=1487461913

Good luck with the job.

[coreydmc]

Tomorrow I will assemble the exhaust manifolds back on the heads. I picked up some high temp manifold gasket RTV sealer to use on both sides of the exhaust manifold gasket. I have been reading that some people say don’t use anything on the gaskets because the temp is to high and others say including DMCH write up to use a small amount of RTV on both sides. Makes sense to me to use it because it will fill in any perfections. Just trying to find out the correct way so I don’t have to do it again.
Thanks!

[DMC-81]

Tomorrow I will assemble the exhaust manifolds back on the heads. I picked up some high temp manifold gasket RTV sealer to use on both sides of the exhaust manifold gasket. I have been reading that some people say don’t use anything on the gaskets because the temp is to high and others say including DMCH write up to use a small amount of RTV on both sides. Makes sense to me to use it because it will fill in any perfections. Just trying to find out the correct way so I don’t have to do it again.
Thanks!

You are welcome.

[coreydmc]

Stayed up last night. Job is all done. Thanks DMC-81 for the advice and picture!

[DMC-81]

Stayed up last night. Job is all done. Thanks DMC-81 for the advice and picture!

Excellent. You are welcome, glad that it was helpful.

[David T]

Typically you should not use a sealant (even high temperature) on the exhaust manifold gaskets. That said, sometimes it is necessary especially if there is a need to hold the gaskets in place because there are no studs. As for using too much Never Seize, if the studs loosen up or break it is because the holes in the exhaust manifold are not large enough and when the parts expand they put huge sideways stresses on the studs. After a few cycles bad things start happening. Cast iron expands a LOT under all of that heat and if you don't allow for it things happen. If the head surface is flat and the manifolds are flat the gaskets should seal properly without the need for any sealant. In fact, back in the 80's many cars didn't use gaskets. The theory was, let them leak, air would get in, the oxygen would help to burn any excess HC and the tailpipe emissions would be lowered. Didn't work so well. It raised engine bay temps, was noisy and reduced HC insignificantly. It caused may automakers to go to an air injection system, adding an air pump and pumping air into the exhaust manifolds. That was eventually discarded because the systems didn't last long.

[DMC-81]

Typically you should not use a sealant (even high temperature) on the exhaust manifold gaskets. That said, sometimes it is necessary especially if there is a need to hold the gaskets in place because there are no studs. As for using too much Never Seize, if the studs loosen up or break it is because the holes in the exhaust manifold are not large enough and when the parts expand they put huge sideways stresses on the studs. After a few cycles bad things start happening. Cast iron expands a LOT under all of that heat and if you don't allow for it things happen. If the head surface is flat and the manifolds are flat the gaskets should seal properly without the need for any sealant. In fact, back in the 80's many cars didn't use gaskets. The theory was, let them leak, air would get in, the oxygen would help to burn any excess HC and the tailpipe emissions would be lowered. Didn't work so well. It raised engine bay temps, was noisy and reduced HC insignificantly. It caused may automakers to go to an air injection system, adding an air pump and pumping air into the exhaust manifolds. That was eventually discarded because the systems didn't last long.

David, that was not my experience. As I said, the studs loosened up because of vibration/flexing of the engine. The holes were not an issue. Too much of a good thing can have detrimental effects...just like too much di-electric grease. I had an annoying problem with the dash warning lights coming on after a battery install in the same daily driver car. After months of frustrating troubleshooting, I traced it to an excessive amount of di-electric grease applied by the auto parts store when they installed the new battery. I wiped off the excess, reinstalled the terminals, and BOOM, problem solved.

[Ron]

I picked up some high temp manifold gasket RTV sealer to use on both sides of the exhaust manifold gasket.
You do not want to use RTV sealer.

If you have imperfections in the head, it might make sense to use RTV High-Temp gasket MAKER, depending on how bad it is.
If you have imperfections in the manifold, you should have them resurfaced.
You are better off without RTV if the surfaces are ok because it is only good to 650F.

Note some re-sellers say you can use it on exhaust, but the official site only lists "Valve covers, oil pans, timing covers, and thermostat housings" on their Application tab.

EDIT: If you must/do...Don't use the Permatex RED, use something like Permatex® Sensor-Safe High-Temp RTV Silicone Gasket Maker (https://www.permatex.com/products/gasketing/gasket-makers/permatex-high-temp-red-rtv-silicone-gasket/).

[Ron]

David, that was not my experience. As I said, the studs loosened up because of vibration/flexing of the engine. The holes were not an issue. Too much of a good thing can have detrimental effects...just like too much di-electric grease. I had an annoying problem with the dash warning lights coming on after a battery install in the same daily driver car. After months of frustrating troubleshooting, I traced it to an excessive amount of di-electric grease applied by the auto parts store when they installed the new battery. I wiped off the excess, reinstalled the terminals, and BOOM, problem solved.+1

I've always make sure the threads are clean then put a dab on my finger and rolled the threads in it. Plenty!
This weekend, I removed exhaust bolts and nuts that I put in 389 Hypo manifolds 18 years ago (and it basically sat for the last two years) -- No problems.

[David T]

Once heated the Never Seize becomes a powder and is not going to make things shake apart. If the parts loosened up it is because the holes in the manifold were not large enough to allow some expansion or you did not torque properly. No one else has experienced this problem so it is something unique to the way you did it, not the use of Never Seize.

[DMC-81]

Once heated the Never Seize becomes a powder and is not going to make things shake apart. If the parts loosened up it is because the holes in the manifold were not large enough to allow some expansion or you did not torque properly. No one else has experienced this problem so it is something unique to the way you did it, not the use of Never Seize.

David, that is an incorrect assumption, and it's pretty humorous for you to suggest that I didn't torque the studs properly. I always research and fastidiously use proper torque specs, as my posts here will indicate.
Like I said previously, an excess amount of the compound WAS the cause. Removing the excess on the same studs installed into the same manifold with the same hole diameter resolved the problem.

By the way, here are the directions on a Never Seize product:

DIRECTIONS:

For best results, part surfaces must be clean and free of grease.
Apply a light coating of product to parts.
Assemble parts.
Wipe away any excess compound.



https://www.permatex.com/products/lubricants/specialty-lubricants-anti-seize/permatex-anti-seize-lubricant-2/

[David T]

I never said to get sloppy with the stuff but I never had the hardware loosen up because of Never Seize either. What I have learned over the years, if the holes in the manifolds make it tight to install over the studs, the expansion and contraction over time will loosen things up and/or fracture the studs. I always check for enough "slop" to allow for expansion. If necessary I enlarge the holes. The surface where the nut rides on the manifold must be flat and square and I use flat washers. If you install the long threaded end of the studs into the cylinder head it is possible you "bottomed out" on the threads on the "short" side and hit your torque before you actually got the joint under full compression. I also like the S/S hardware kit that PJ Grady sells, very nice but pricey. When working on marine engines they use brass nuts and I never had a problem removing them even if Never Seize was not used. Removing steel or S/S hardware from an aluminum head is always problematic especially if Never Seize is not used.

[DMC-81]

I never said to get sloppy with the stuff but I never had the hardware loosen up because of Never Seize either. What I have learned over the years, if the holes in the manifolds make it tight to install over the studs, the expansion and contraction over time will loosen things up and/or fracture the studs. I always check for enough "slop" to allow for expansion. If necessary I enlarge the holes. The surface where the nut rides on the manifold must be flat and square and I use flat washers. If you install the long threaded end of the studs into the cylinder head it is possible you "bottomed out" on the threads on the "short" side and hit your torque before you actually got the joint under full compression. I also like the S/S hardware kit that PJ Grady sells, very nice but pricey. When working on marine engines they use brass nuts and I never had a problem removing them even if Never Seize was not used. Removing steel or S/S hardware from an aluminum head is always problematic especially if Never Seize is not used.

No David, you didn't say sloppy, but you said:


MAP gas doesn't get it hot enough. An Oxy-Acetalyne torch will do it. Heat it up to cherry red, let it cool, heat it again and then remove it, along the threads, from the head. Then Heli-coil it. Use plenty of Never Seize when you put it back together.

And then:

Never Seize. Use liberally on all of the exhaust hardware but be careful, it can get messy.

... which is more than the product's instructions of a light coating. :rolleyes:

[David T]

We can argue over this back and forth. We both agree it should be used but maybe not as much as I said and maybe more than "a light coating". In any case too much of anything is not good but even if you overuse the stuff I don't think it is responsible for your parts coming loose especially when you say you used a "light coating". Besides, the stuff is like blood, a little bit gets all over the place if you aren't careful!