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?14...-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.