Broken Bolt In Upper Manifold, But Why?

Discussion in 'SN95 V6 Mustang Tech' started by Jong99, Jun 10, 2013.

  1. Hi all,

    I was torquing down the upper intake manifold bolts on my recently acquired 99 v6 yesterday (according to the tightening order/torque specs in the Chilton's guide) when the very first one snapped in half.

    I thought there might be something wrong with the wrench so I switched to a different (brand new) wrench for the rest of the bolts. Only three stopped at what felt right for the specified torque while the rest seemed like they were turning way too far. I then retested the original wrench with the same results.

    My assumption is that a previous owner overtightened the bolts and the lower manifold is therefore ruined, so I'll be looking for a new one now. But before I make the same mistake again I want to understand exactly what happened here. Why did the bolt snap if the wrench was not the problem? If the bolts/manifold threads were ruined by the previous owner then why wouldn't the bolt just spin in the hole?

    Thanks in advance for any insight into this problem.
  2. What torque spec? Was there any debris under the head of the bolt that would cant the head sideways? Is the manifold flat and true under the bolt head?