Why Exhaust Manifold stud broke?

[nlarr81]

hi guys.....
i heard a exhaust leak on my way home from work.......let her cool off and checked it out.....i have one broken manifold stud (back driverside)
as i'm looking i cant seem to find why it broke and i dont want to fix it just to brake it again or brake more studs.....
all the hangers are good, bolt,motor/tranny mount.....it it just a age thing or am i missing something?
should i juust go ahead and do them all?

thanks

 

[NEVERDONE86]

metal fatigue is why. the constant hot, cold, hot, cold, and the humidity kill the studs. yes i would pull the heads and replace all of them before they all break when you try to take them off in the future. i had 90% of the studs break when i rebuilt my 86 2.9l. i drilled them out and retapped/replaced them with larger grade 8s. hope this helps.

 

[adsm08]

They break because Ford doesn't put donughts between the manifolds and Y-pipe.

Usually a broken stud means you have a warped manifold because it's the stress of the manifold warping that breaks the stud.

The V-8s and V-10s are notorious for this.

 

[85_Ranger4x4]

They break because Ford doesn't put donughts between the manifolds and Y-pipe.

Usually a broken stud means you have a warped manifold because it's the stress of the manifold warping that breaks the stud.

The V-8s and V-10s are notorious for this.

The difference of expansion rates between cast iron manifolds and aluminum cylinder heads on the mod motors have a lot to do with it too.

 

[nlarr81]

thanks guys.....does the head have to come off?...are the stude threaded or pressed?
should i replace the manifold to? or is it just waisting money?