Exhaust Manifold Stud Failure
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
For the record, my 2001 V10 came with stainless studs from the factory.
What appears to be the problem is the nuts themselves corrode/weld themselves to the manifold. As the manifold expands and contracts from heating and cooling, it drags the nuts with it. And eventually breaks the studs.
It appears the studs themselves are defective from a bad heat treating process, where the shoulder is built up is where they are heated and compressed lengthwise. This is usually where they break. Although in my case, there were two that broke down in the head, nowhere near the shoulder.
Kinda like the old FE series engine manifolds cracking. Same cause.
What appears to be the problem is the nuts themselves corrode/weld themselves to the manifold. As the manifold expands and contracts from heating and cooling, it drags the nuts with it. And eventually breaks the studs.
It appears the studs themselves are defective from a bad heat treating process, where the shoulder is built up is where they are heated and compressed lengthwise. This is usually where they break. Although in my case, there were two that broke down in the head, nowhere near the shoulder.
Kinda like the old FE series engine manifolds cracking. Same cause.
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
Originally Posted by krewat
For the record, my 2001 V10 came with stainless studs from the factory.
What appears to be the problem is the nuts themselves corrode/weld themselves to the manifold. As the manifold expands and contracts from heating and cooling, it drags the nuts with it. And eventually breaks the studs.
It appears the studs themselves are defective from a bad heat treating process, where the shoulder is built up is where they are heated and compressed lengthwise. This is usually where they break. Although in my case, there were two that broke down in the head, nowhere near the shoulder.
Kinda like the old FE series engine manifolds cracking. Same cause.
What appears to be the problem is the nuts themselves corrode/weld themselves to the manifold. As the manifold expands and contracts from heating and cooling, it drags the nuts with it. And eventually breaks the studs.
It appears the studs themselves are defective from a bad heat treating process, where the shoulder is built up is where they are heated and compressed lengthwise. This is usually where they break. Although in my case, there were two that broke down in the head, nowhere near the shoulder.
Kinda like the old FE series engine manifolds cracking. Same cause.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Originally Posted by 99f350sd
The original studs are galvinized steel. The galvy coating lasts pretty long..
Definitely stainless. Looked like stainless, drilled like stainless. The studs.
The nuts were crap. Hence the locking to the manifold, manifold expands and contracts, studs break.
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
Originally Posted by 99f350sd
The studs the dealer sells per tsb are copper coated stainless totally non magnetic..
Dick
Dick
Most stainless steel bolts on the market sold in hardware stores are made of 18-8 stainless steel which still has a very mild magnetic attraction. There are bolts made of 304 and 316 stainless as well but there cost considerably more.
I also don't see how anyone could ever rust through a set of cast iron manifolds either. Most are at least .500" thick. Hell the set of cast manifolds were on my 74' F-100 when I bought it and they were over 26 years old then.
Last edited by dkf; Nov 13, 2007 at 11:34 AM.
Lead Driver
Joined: May 2003
Posts: 9,303
Likes: 48
From: Lyndonville, Vermont
The reason they coat them is they are going into aluminum. Its a corrosion thing. The nuts that they spec'ed out were supposed to be stainless but were highly magnetic..
I spent many threads talking about this topic in the past I'm not making this stuff up.
I even have the tsb and the part numbers somewhere..
Dick
I spent many threads talking about this topic in the past I'm not making this stuff up.
I even have the tsb and the part numbers somewhere..
Dick
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