2003 Exhaust manifold

[Schludwiller]

I had 2 broken studs in addition to the cracked manifold.

[Toy Man]

I had several broken studs also. (and then Nissan sent the wrong studs.) Was in the shop three days getting it all sorted out.

Toy Man

[OffroadX]

Are you sure they were broken before they started trying to remove the manifold? I've heard of studs breaking when a wrench is put on them, but I don't know that they've broken from stress.

Brent

[ChuckH]

Yes, some people have had broken studs. I think Andrea in PNWX had one or two broken studs too. I think what happens is the manifold not only cracks but also warps in some cases. The warping is what breaks the studs. I can't wait to see what mine look like when I finally get around to getting headers on.

[OffroadX]

Right, that was the original problem, warped manifolds pulling on the studs. Looks like they've come full circle.

[boodie]

I think what happens is the manifold not only cracks but also warps in some cases.

Strangely enough, I had the warping problem on my '86 Toyota-based RV. The 1-ton truck had 100K on it, and the exhaust manifold (4-cyl) warped. It was obvious with a long straightedge.

I'm the 2nd owner, and after talking with an (unrelated) engineer, he speculated that after years of heat-cycles, the manifold changes crystalline structure, allowing warpage. He also said it should habe stabilized, and I should no longer have a problem with it warping.

...OK...Sounds good to me...

It only cost $35 to have the manifold surface-ground; I installed oversize studs at the same time...

No cracks...cross fingers...

[X-Phile]

See, I got a totally different story from the mechanic at the dealership that does my work. I was told that the reason the bolts break is that the exhaust does not have enough play to move with the engine. As far as the manifold itself, yeah he said they all have that flaw.

But whats right about the bolts?

[O1SalsaX]

When I had my manifold changed they said that it sheared two of the studs in the block. That must've really sucked. Having to drill it out and tap them. Well, I guess it was easier to do since they had the cylinder head off to change the head gasket at the same time.

[Schludwiller]

Originally Posted by X-Phile

See, I got a totally different story from the mechanic at the dealership that does my work. I was told that the reason the bolts break is that the exhaust does not have enough play to move with the engine. As far as the manifold itself, yeah he said they all have that flaw.

But whats right about the bolts?

Most everything I've heard goes along with your mechanic's description. We have people in our club who have broken the same manifold in a matter of months, so it has nothing to do with breakdown of the metal but rather stress on it from the exhaust leveraging the manifold.

And Brent, mine had at least two sheared off bolts as well . The shop manager said it was a bitch to get the thing repaired.

[boodie]

Originally Posted by ChuckH

I can't wait to see what mine look like when I finally get around to getting headers on.

ChuckH -

What headers are you looking to put on???

[Schludwiller]

Originally Posted by ChuckH

Well I've got those nice big Calmini stickers and those are worth mucho power gains!

That must be why you have 3 on your truck. Tripple HP

BTW thanks for the free delivery.