Exhaust Manifold

 What is an exhaust manifold?

The exhaust manifold is the first component of a vehicle's exhaust system. It bolts to the engine's cylinder head and collects the exhaust gasses from the individual exhaust ports, combining them in one outlet to flow through the rest of the exhaust system and eventually out the tailpipe. 

In addition to playing such an integral role in your car or truck's exhaust system, an exhaust manifold is also important for the safety of its occupants. With the help of an exhaust manifold gasket, it prevents the toxic exhaust fumes from sneaking into the vehicle cabin and harming those that are in it.

A majority of vehicles have exhaust manifolds that are constructed out of cast iron, but some vehicles have tubular steel manifolds made from either mild steel or stainless steel. Some vehicles also have a catalytic converter incorporated into the exhaust manifold.

How do I know if I need an exhaust manifold replacement?

You will need an exhaust manifold replacement if your exhaust manifold develops cracks or if your exhaust hangers are damaged. 

The most common reason for exhaust manifold failure is cracking from age and/or the frequent heating and cooling cycles it endures. As the manifold heats up, the metal expands; as it cools, the metal contracts. Over time, this will weaken the casting and will eventually cause the manifold to crack.

The second common reason for failure is from broken exhaust system hangers.  Other exhaust parts, like your catalytic converter or muffler are held to the frame of your car by round rubber "hangers."  If those hangers get worn out or break, the weight of your exhaust can start to pull on the exhaust manifold, wearing it out over time.   

What is a leak in the manifold?

A leak in the manifold occurs when the manifold gasket breaks down, allowing exhaust gas to exit from in between the engine and the exhaust manifold. 

A metal and rubber gasket seals the space between the engine and the exhaust manifold to keep the exhaust gasses from leaking out into the engine bay.  If this gasket wears down it might let some of the gasses slip out.  If this is happening, you might notice that your engine sounds louder, it's harder to accelerate, or there is a burning smell coming from the engine bay. 

Why is my manifold leaking? 

Your manifold may be leaking because of a worn exhaust manifold gasket.  The gasket that seals the space between the engine and the exhaust manifold can wear out due to extreme temperatures, oil or coolant leaks, or simple wear and tear over time. 

Exhaust Manifold vs Header:

Headers do the same job as exhaust manifolds but are specialized performance parts.  While a typical exhaust manifold has a blocky exterior and is made of cast iron, headers are made up of separate steel tubes that take the exhaust gas from the exhaust ports to a collector tube, on to the rest of the exhaust system.  Headers have more interior space, and smoother insides than stock exhaust manifolds which allows the exhaust gasses to flow more easily.  That can help your engine produce more power. 

Do headers replace the exhaust manifold? 

Headers are a performance upgrade that can replace an exhaust manifold.  Headers can help increase your engine's power output when used along with other upgraded exhaust parts.  Replacing the exhaust manifold with headers, but keeping the rest of the exhaust stock can lead to back pressure that diminishes the advantage gained by smoother exhaust flow in the headers. 

Some sports cars, as well as some Jeeps may come from the factory with tubular steel exhaust manifolds. 

How much does it cost to replace an exhaust manifold?

Replacing an exhaust manifold can cost anywhere from around $300 to over $1000.  The price will vary depending on the model of your car, whether you use aftermarket or OEM parts, and whether you have the work done at a dealership or an independent shop.  The manifold itself can range in price from about $100 to $400, with labor costing from about $200 to $600. 

Can I replace an exhaust manifold myself?

The degree of difficulty in replacing an exhaust manifold varies from vehicle to vehicle, although many replacements can be done at home by someone with basic hand tools, a good set of instructions, and a bit of automotive knowledge.

How to replace an exhaust manifold:

The process for a typical exhaust manifold replacement is: 

1.    Apply rust penetrant to the manifold bolts.  Give the rust penetrant time to work.

2.      Remove the bolts that hold the exhaust manifold to the catalytic converter or exhaust pipe.

3.      Remove the bolts that hold the manifold to the cylinder head.

4.      Pull out the exhaust manifold. 

5.      Pull off the exhaust manifold gasket. 

6.      Scrape any gasket residue from the cylinder head with a razor.  Be sure not to let any debris fall into the cylinder head. 

7.      Clean any remaining gasket residue with a solvent. 

8.      Line up a new exhaust manifold gasket.

9.      Lift the new exhaust manifold into place. 

10.  Insert the bolts that hold the exhaust manifold to the cylinder head. 

11.  Insert the bolts that hold the exhaust manifold to the catalytic converter or exhaust pipe.

12.  Tighten all the bolts to the manufacturer's recommend torque setting with a torque wrench.