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How to Weld or Braze an Exhaust Manifold Leave a comment

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Manifold Repair Tips


A vehicle’s exhaust manifold is designed to pull combusted gases (exhaust) away from the engine. These combusted gases are extremely hot, and the high temperatures cause the metal manifold to expand. Then, when the car is not running, the metal cools and contracts. Over time, this constant expansion and contraction can cause a manifold to crack and leak exhaust.

If your vehicle’s manifold is cracked or broken, exhaust can leak under the hood and into the cab of the vehicle, rather than through the exhaust system and away from the back of the vehicle. Hot exhaust underneath the hood can damage plastic components, while exhaust in the cab is extremely dangerous to passengers.

Signs of a Damaged Exhaust Manifold


Knowing the signs of a damaged exhaust manifold will help you quickly diagnose and solve the issue.

  1. Strange noises:  If you notice that your vehicle is running a little louder than normal, that could mean that there’s a leak in your manifold. If your manifold is damaged, gas can escape through the exhaust system, which would make your engine sound quite noisy.
  1. Poor gas mileage: A crack in your manifold can make your vehicle less fuel-efficient. If it seems like you’re heading to the gas station more often lately, you should check your manifold for damage or make an appointment with a professional mechanic.
  1. Bad odor: Because the manifold is responsible for dealing with engine exhaust, a crack can cause exhaust to get in the car or underneath the hood. Strange smells are one of the first signs of a damaged exhaust manifold.
  1. Lack of engine power: Leaks in the exhaust can cause a lack of acceleration power in the engine. It might seem hardly noticeable at first, but it can cause more serious engine issues if ignored.
  1. Check engine light: A crack in the manifold can cause your check engine light to turn on. Don’t ignore a check engine light! You could save yourself a lot of stress and money by diagnosing and fixing the problem early on.


How to Repair a Cast Iron Manifold

There are two ways to perform cast iron manifold repair: brazing and welding. Here are some expert tips for manifold repair that will help you achieve optimal results.


Cast Iron Manifold Repair – Welding

To repair your exhaust manifold, start with the Muggy Weld Cast Iron Exhaust Manifold Repair Kit. It contains 72 and 77 electrode rods that are perfect for this type of repair.

  • Begin with the 72 rods – they are formulated to join contaminated and heat-affected cast iron, making them ideal for burnt and cracked exhaust manifolds. If you have dirty cast iron that you need to weld, the 72 rod is ideal for bonding to the metal with its high porosity.
  • After sealing the crack with the 72 rods, chip off the slag.
  • Use the 77 rods to reinforce the weld – the 77 is crack-resistant, very strong, and porosity-free. The specially designed coating converts impurities into slag. The 77 rods are softer than nickel rods, allowing them to stretch up to 300% more to prevent the base metal and weld from cracking.
  • Let the weld cool naturally and try to keep it out of the wind to allow it to cool slowly.

You can make this type of manifold repair with a very small welder and still fix exhaust manifolds for a variety of vehicles, including cars, RVs, trucks, buses, and more.


  • Never weld more than 2 inches at a time and let cool for 2 minutes between passes. For some cast irons, you may only want to weld an inch or less and let it cool for 1 minute between passes
  • Low and slow is the key to a sound weld with cast iron


Cast Iron Manifold Repair – Brazing

Manifold repair can also be done by brazing the cast iron. This is an excellent option for those who do not have access to a welding machine. The Muggy Weld SSF-6 High Strength 56% Silver Solder is an ideal replacement for fluxless silver solder coils, our flux-coated rod has a high thin flow, flows easily, and can be used with a variety of metals at over 70,000 psi.


Muggy Weld for Manifold Repair Necessities and More

Muggy Weld is a leading welding supply company. We are proud to be a family-owned and operated company that provides premium products that are always manufactured in the USA. Please browse our online collection and don’t hesitate to contact us with any questions!

Check out the Muggy Weld YouTube channel for welding tutorials and more.

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