[NYBo]

Some of the exhaust manifold studs on my Dakota 3.9L need to be replaced (threads are gone and there is an exhaust leak as a result). What is the best strategy to give me the best chance of removing them without them breaking off? I am hoping to be able to do this with the manifold in place.

 

[dana44]

I hear heat and wax works pretty good.

 

[NYBo]

Should I run the engine up to operating temperature or just use a torch on the stud itself?
Wax?

 

[KOG]

You'll have a much better chance with the manifold off. I've heard that acetone and transmission fluid mixed 50/50 is the best penetrating fluids you can get. Haven't tried it yet, but I've got the stuff on hand for the next time I need it. Another possibility on a stud is to drill through the stud (1/8" is enough) and then use CRC Freeze Off or a similar spray to shrink the stud and remove it.

 

[ImperialCrown]

Agree. There probably won't be enough of the stud to grasp and turn safely with the manifolds in place. Clearances will be tight in there anyway even with the V6, especially if you need to get a torch in there.
You will want to heat the head area where the stud threads in to expand the metal, not directly heating the stud itself.
Using a stud removal tool like this ( http://www.amazon.com/OTC-6986-2-16-Stud-Remover/dp/B005LTJ0G0 ) offers a good grip and less likelihood of breaking the stud off. It also won't mar the stud when installing the new one, unless you choose to reinstall the manifolds with plain bolts and washers.
Getting the studs out in one piece the first time is very important. Otherwise you may have to remove the head to get the broken piece drilled out.

 

[NYBo]

Thanks for all the tips. I think I'll bite the bullet and remove the manifold even though the studs are still full length. No way I want to pull the head to have a broken-off stud removed!
IC, you linked to a 5/16" stud remover, but it appears the ones on my engine are 1/4". Can anyone verify the size?

 

[KOG]

Tow ways to know for sure. Either measure a stud with your dial caliper or take a nut to Lowes or HD and match it to see what size it is.

 

[NYBo]

Well, they USED to be 1/4" but the threads are rusted off!

 

[CudaPete]

Is there enough meat left that you can run a smaller size (3/16") die down the existing studs and install some new brass nuts?

 

[NYBo]

Plenty of meat, not enough clearance to turn the die.

 

[KOG]

And you don't even want to do that anyway.

 

[valiant67]

I had a 3.9 V6 where the center studs were broken but the bolts at the ends of the manifold were OK. Once the manifold was off, there was a non-threaded posartion of the stud exposed that I could grip with vice grips and remove. Since the stud was broken I expected it to be hard to remove. However, it was not.

 

[TWX]

I pulled 'em on the '78 Cordoba in-car, with probably 140,000 miles on the engine at the time. Ran one nut down all of the way to the unthreaded part, then put another nut on and tightened them against each other, then spun it off with the inner nut. Nothing broke when I did it. Had to pull 'em to do headers, needed to use header bolts.