HOW TO REMOVE EXHAUST STUDS?

DECEMBER 7,2021

👋  Every owner of a car has to face challenges like fixing problems with different parts of the car. The most common problem is exhaust studs breaking.

But what exactly is the meaning of an exhaust stud? Why do they break and how to remove them?

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  • "Exhaust Manifold Leaks Can be Dangerous, as Well as Cause Other Costly Problems."



"Exhaust Manifold Leaks Can be Dangerous, as Well as Cause Other Costly Problems."


1. WHAT IS AN EXHAUST STUD? 

Every engine has an exhaust manifold that helps to gasses back out from the exhaust valves through the exhaust system. Since the exhaust manifold isn’t built into the engine’s head, it has to be bolted on. The way this is often done is using studs or bolts. The problems start when these studs or bolts rust out or break either inside the head or flush with the head. 

2. WHY DO EXHAUST STUDS BREAK?

There’s a couple of reasons why studs tend to break. One has to do with heat. Just like most things out there, metals expand and contract with heat. Each time you start the engine, and it warms up to its operating temperature, the studs will slightly expand. The exhaust manifolds are formed from the factory using fine grain cast iron, and like most metals, it expands and contracts during duty cycles of heating and cooling.


This expansion happens naturally, and at first, the manifold and mounting studs are in a state of “elastic deformation.” Elastic deformation is basically expansion and contraction over a period of time retaining the original size and shape. Each duty cycle will provide tension stress on the studs or bolts that hold the manifold in place. The mounting hardware exhibits flexibility over time.


However, as the manifold continues to expand and contract more dimensionally, each consecutive time creates larger and larger tension forces that move beyond the elastic state of deformation and become what is referred to as “plastic deformation.” Basically the manifold stretches beyond return and fractures the mounting stud, leaving the manifold permanently deformed and dimensionally changed. This expansion and stretching of the manifold bolts over numerous duty cycles eventually causes too much tension on the bolt(s), stretching them beyond capacity and causing them to fail.


Aside from heat, there’s always rust. Oxidation happens over time, especially if the car is frequently exposed to the weather. Having a rusted out exhaust stud is nothing out of the ordinary as it’s not so uncommon to find entire exhaust manifolds rusted to nothing. 

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3. WHY YOU SHOULD FIX AN EXHAUST MANIFOLD 

Sometimes an exhaust manifold starts to leak, because a mounting bolt or stud has broken. Exhaust manifold bolts and studs both suffer the same fate; of getting brittle from too many heating and cooling cycles. Along with expansion and contraction of the whole system, something has to give. As a result, making broken bolts or studs a fairly common problem.


If your vehicle has been diagnosed with an exhaust leak, you'll probably have some unanswered questions, such as how it will affect your vehicle's performance and whether it's safe to drive. While the severity of exhaust leaks varies, they'll almost always create one or more symptoms. And if you don't get it fixed, it could lead to other problems for your vehicle later down the road.


Exhaust leaks are problematic for several reasons. First, they can throw off sensors, which may cause your engine to burn too much or not enough fuel.


First, exhaust leaks are bad for the environment because they often release exhaust gases before those gases are able to pass through the catalytic converter. Second, exhaust leaks can pose a risk to you and your passengers' health. Finally, the repair for this can be a nightmare as well.

4. HOW MUCH TO REPLACE IT?

The average cost for an exhaust manifold replacement is between $996 and $1,099. Labor costs are estimated between $248 and $314 while parts are priced between $748 and $785. Estimate does not include taxes and fees.


The good news today is, there are better tools and techniques for making this repair easier

5. HOW TO REMOVE BROKEN STUDS?

So you’ve decided to remove your exhaust manifold, and you’ve felt that notorious crack of a stud under your tool. Now what?

At this point, you have several options at your disposal. Before we get to removing the broken stud, there are two crucial pieces of information you need to internalize.


-Studs are generally not torqued too tight

-A stud always breaks at an angle

Knowing these two facts is vital for what we’re about to do.

#1 - Two-Nuts Method


To begin with, find 2 non self locking style flange nuts of the same size and pitch as the stud that you're working on removing. (The same nuts as were removed to access this stud are ideal). Thread one of the nuts onto the stud to be removed with the nut being installed upside down. Next, thread the 2nd nut onto the stud so that the flanges meet and that there is at least a couple threads extending from the top nut. With an open ended wrench on the bottom, or most inner nut, tighten the two nuts together as tightly as seems safe without the wrench(s) slipping. With the nuts double jammed together, place a wrench on the bottom nut and using appropriate force, the stud should unthread.

#2 - Drilling the Broken Bolt Out of the Head


The first step in this particular method is taking a metal punch and tapping the broken stud. You’ll need to find a hammer that will allow you to do this as not all engine bays are permissive in this regard. What you’re doing is creating a small divot in the broken stud. That divot is necessary to seat the pilot hole drill bit we’ll use to drill out the stud. Without punching a divot, the chances are that your drill bit would run all over the place or create a hole that is not perpendicular to the head. After we’ve tapped the divot, take a small drill bit smaller than the stud’s diameter, and drill a pilot hole in the stud. Sometimes you’ll find that reversing the drill bit out of the stud is all it takes to remove it. 

#3 - Stud Extractor Method


A stud extractor is a tool specially designed for extracting broken bolts. The universal design of this tool allows you to clamp down on any damaged, rusted or broken stud. As you apply turning motion the tool has a tightening jaw that binds in on to the bolt and removes it with ease.

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6. HOW TO USE A STUD EXTRACTOR TOOL

The stud extractor's simplistic design is in the three jaws that grip the broken stud with amazing strength allow even the toughest frozen studs to be removed quickly and easily. The first thing is to make sure the small nut is loosened up enough for the extractor to slide over the nut. The extractor nut has left-hand threads so turning the nut to the right (clockwise) opens up the jaws, and turning the nut to the left (counter-clockwise) closes the jaws. Then slide the extractor over the broken stud, and then tighten the nut by hand, and then using the 2 adjustable wrenches tighten the nut securely. The stud extractor will remove studs and within a couple turns the stud will be on its way out. Then, use the same adjustable wrenches loosen the nut (clockwise) and remove the broken stud from the extractor.

There's not much that can be more frustrating than dealing with a stud that has been broken off. Fixing a broken exhaust manifold stud can be difficult however, it’s fixable. Methods shown above are some of the most common solutions used in the industry and will save you a lot of money!



Josh J. Gur - CEO

CEO of Sanrico

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