Ask the Expert: What are the biggest challenges a technician faces when trying to repair a broken exhaust manifold stud?

Feb. 27, 2016
There are actually three common challenges when attempting to repair a broken exhaust manifold stud.

Q: What are the biggest challenges a technician faces when trying to repair a broken exhaust manifold stud? 

A: There are actually three most common challenges when attempting to repair a broken exhaust manifold stud. 1) Access to the damaged stud or bolt is always limited when working on the cylinder heads. Working by the firewall or behind the shock (strut) tower presents some real challenges in order make the repair. 2) Drilling perfectly straight into the broken stud, and 3) drilling perpendicular. Most attempts to drill free-hand result in the drilling operation being off-center at least 1/32” - 1/16” or more, and typically about 6-7 degrees from the vertical axis centerline. These “off-center” and “off-perpendicular” attempts significantly increase the torque required to extract the stud. In other words, taking a bolt out at an angle and off-center is far more difficult than removing it straight-out.

Lastly, with limited space, getting an air drill into the perfect spot to drill dead-center and straight is challenging. Other options, including welding, can be effective. But in order to get a weld to “stick,” the remnant needs to be cleaned and free of all rust and corrosion. Welding temperatures need to be perfect so that the aluminum head is not damaged, and you need much more room to get a welding head in the location. Keep in mind, that since the mid 2000 engine years, many manufacturers’s moved to a stainless steel stud, or bolt, where special wire is required for those versus older models. Also, welding hardens the stud and once welding is attempted, it significantly increases the challenge to remove the broken piece. Lastly, welding is not always 100 percent effective, simply because a burr is created from the threads stretching and unwinding like a coil spring. Once unwound, the thread breaks off and jams into the soft aluminum acting precisely like a lock washer, making extraction nearly impossible with a welder. That’s where the ProMAXX ProCutter accessory really pays off.

Information provided by: ProMAXX

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