The exhaust manifold is the first part of any vehicle’s exhaust system. Tasked with the important duty of collecting gases from numerous cylinders into a single pipe, an exhaust manifold is usually a stainless steel or cast unit. It primarily delivers the exhaust gases to the exhaust pipe. Since the job it does is so important, a cracked exhaust manifold repair is somewhat pricey.
It’s not only the price of repairing the cracked bit but there’s also the high labor costs. With all that in mind, you might be wondering what’s all this fuss about an exhaust manifold? Well, today we answer that question. We’ll look into what an exhaust manifold is, why and how it cracks, how to repair it, and much more.
What Is An Exhaust Manifold?
Depending on the type of the vehicle and its engine, there are two types of exhaust manifolds. It can either be a cast iron manifold assembly or a set of pipes. As mentioned before, the exhaust manifold collects burned exhaust gases from the cylinders and delivers them to the car’s tailpipe before it’s finally ejected.
The exhaust gases are simply the burned air/fuel remnants from the combustion process going on in the engine. Over time, due to the constant contraction and expansion of the components, the manifold might crack.
As scalding hot exhaust gases are released in the process, these cracks/leaks can be extremely hazardous. It can damage other parts of the engine and affect engine performance as well.
Occasionally, a broken mounting bolt makes the exhaust manifold leak. In this case, the mechanic must remove the broken stud or bolt. They may charge an extra fee for this, depending on the complexity of the situation. Very briefly, this is the process that follows:
- Determine if there is a crack in the manifold
- Extract and change fault exhaust manifold
- Check exhaust bolts, clean the cylinder head
- Install new exhaust manifold and gasket
- Start engine to inspect for any exhaust leaks
The default engine in most single cars is V-shaped with two exhaust manifolds connected to it. One of them is for one cylinder bank while the other is for the second cylinder bank.
Cast Iron Exhaust Manifold
Generally, cast iron exhaust manifolds last longer. Thanks to the use of high-quality parts, the cracked exhaust manifold repair cost may not be that high. Modern cars cut down on the bulk so the exhaust manifolds are designed to fit into smaller corners and spaces.
If an owner wants more performance and power, they might swap the cast iron manifold for headers. These aren’t the most durable but again, that’s not what they were made for. Moreover, those manifolds can be somewhat heavy and get brittle with time and age. The decomposition and aging can increase the exhaust manifold repair charges.
Tubular Steel Exhaust Manifold
Tubular steel exhaust manifolds have better airflows, which is why they can often be spotted in performance cars, such as sports cars or anything that requires more horsepower. As you could tell from the name, this style of a manifold is made from stainless steel or regular steel depending on the manufacturer.
Stainless steel is more expensive to produce, but that adds to its reliability and longevity. In comparison, mild steel doesn’t last as long. This can lead to a frequent need for repairing or replacing exhaust manifolds.
Symptoms Of A Cracked Exhaust Manifold
How do you know that the exhaust manifold in your car is broken? Look out for these signs.
When you lift the hood of the drive, an unpleasant odor of burning rubber or plastic greets your nostrils. Gaskets feature coatings that give off a plastic or rubber smell when burned or overheated. Damaged manifolds don’t do their job properly – they don’t transfer heat and the result is damage in the gaskets and condensed exhaust leaks.
A common symptom of a leaking exhaust manifold is a sudden or gradual loss of power when you accelerate the vehicle. It becomes very noticeable when your car isn’t as responsive as it used to be. You have to press the pedal harder to get to the next gear. A manifold with a damaged gasket slowly affects acceleration capability, whereas a crack or similar damage will result in similar reactions.
Low Fuel Efficiency
Having to stop by the gas station way more than you had to? When the manifold is damaged, the exhaust doesn’t remain pressurized as it should. Fuel efficiency drops. A new exhaust manifold or gasket could pay for itself in saving fuel within a few weeks.
Loud Exhaust Noise
If there is a hole in the gasket or any part of the exhaust system, it will produce loud sounds while the car is in operation. However, damage to the manifold tends to create tapping or hissing noises around the back of the engine. Not only does the manifold failure cause problems in that area, but it can also damage the catalytic converter.
If that part is damaged, you may hear loud grinding sounds. These sounds tell you that your vehicle’s engine isn’t able to hold compression anymore. It’s best to avoid driving the car till you can get it checked by a mechanic.
When your olfactory or auditory senses aren’t being tingled by a cracked manifold, you can move onto your eyes. Inspect the side of the manifold carefully and you may notice a visible crack there. It could be hairline thin but it might as well be pressed against the engine. Just because you can’t see the damage, that doesn’t mean it’s not there.
Despite the reduction in acceleration power and loud noises, exhaust manifold repair costs are reasonable in value, comparatively speaking.
Reasons Behind An Exhaust Manifold Leak
There could be several reasons behind an exhaust manifold leak that might lead to exhaust manifold repair. Let’s go through some of them now.
Cracked Exhaust Manifolds
The engine is constantly working in high-pressure, and intense temperature situations. A crack in the metal could mean a leak in the manifold. The crack may start out paper-thin at the very first, but with time (and more heat consumed by the manifold), it will begin to increase in size.
At one point, the crack may self-seal when the metal expands. The sound coming from the damage will also become less noticeable.
Leaking Manifold Gaskets
The gasket, which is quite similar to the exhaust manifold, has to tolerate contracting and expanding of the heated metal. The symptoms of failure are similar to the ones you see in a cracked manifold and the problem could exacerbate really fast.
Exhaust manifold gaskets seal the whole exhaust system, making them an indispensable part of the car. When the gaskets fail, it can negatively impact the drivability and performance of the vehicle.
Loose Or Broken Bolts
The studs and bolts holding the exhaust manifold together may get brittle due to the constant heating and cooling processes. Broken bolts are one of the more common problems in this case. But, the repair can still be a nightmare.
Why You Should Do Exhaust Manifold Repair
There really shouldn’t be any questions here at all. If you want your car to deliver smooth performance, you have to maintain every component of the car. When the component is as important as the exhaust manifold, there are so many reasons to be more careful.
Poor Fuel Mileage
A cracked exhaust manifold will give your car poor gas mileage. This happens due to a complex reaction of the oxygen sensor to the exhaust manifold. Not all cars have them, but for the ones that do, it may give an incorrect reading due to a damaged exhaust manifold. When that happens, the engine is prompted to burn through the air faster.
Gases Accumulated In The Cabin
Instead of escaping through the tailpipe, the exhaust gases will gather in the engine bay. Why is that an issue? The climate control system of the car draws air from near the engine bay. With the engine bay filled with exhaust gases, some of those gases may end up inside the car cabin, exposing the riders of the car to toxic fumes.
Damage To Other Parts
Occasionally, a leaking exhaust manifold can damage other components of the engine bay. Hot exhaust gases leaking through a damaged manifold are enough to melt wires or light parts on fire (the ones made of flammable materials).
Failed Emission Tests
Some states or cities require emission testing. Your car will fail that test if it has a cracked exhaust manifold. This problem might even trigger the Check Engine Light. With the CEL on, your car will fail without any further inspection.
Sadly, there’s no quick fix for these manifold issues. Drivers have tried to fight the problem with heat-resistant epoxy, like JB Weld. Although JB Weld is a great product, it simply isn’t capable of withstanding 1,200°F exhaust gases. The only available option is to change the cracked exhaust manifold. These problems should go away once the new manifold is installed.
There are more reasons to fix a malfunctioning exhaust manifold. Under intense use such as towing bulky loads, the temperature inside exhaust manifolds can shoot upwards sharply. The increasing heat forces the manifold to expand, exerting tremendous strain on the studs and/or bolts holding the material to the cylinder heads. Fast forward about a hundred expansion and contraction cycles later, the bolts or studs will fail entirely.
Compare this scenario to the bending of a paper clip. Eventually, it will fall apart in your hand after being tired of the pushing back and forth. Only one part of the manifold is secured to the engine cylinder head, so the exhaust gasket could blow it out. This lets the exhaust gases escape alongside allowing air to get inside the exhaust stream. The O2 sensor is thrown off immediately, giving out weird readings.
If the oxygen sensor assumes that the engine is operating leaner than regular, it will direct for additional fuel to pump into the engine, harming the catalytic converter(s) in the process. Furthermore, with the exhaust manifold expanding and contracting unevenly, the cast iron crack will aggravate the oxygen sensor into giving incorrect readings. Last but not the least, the annoying sounds due to the leak makes for a bitter riding experience.
Diagnosing A Leak In Exhaust Manifold
First things first, start by doing a visual examination of the engine bay. Don’t do this exactly after a drive; let the engine cool for several hours before an inspection. Check for black soot over the manifold, one of the common signs of an exhaust leak. It would be easier on you if the cracks or loose bolts were visible. You can also connect a wrench to the bolts to make sure if they’re torqued.
The easiest way to figure out if there is a leak is by using a vacuum cleaner. Turn the car engine off and place the cleaner in the exhaust pipe. The vacuum must be positioned in such a way that it pushes air into the exhaust. Spray some soapy solutions over the exhaust and check if there are bubbles. If there are bubbles, then there is a leak.
How To Do An Exhaust Manifold Repair By Yourself
Replacing an exhaust manifold leak is relatively easy. You just need a few deep sockets and wrenches to remove the manifold. Light grit sandpaper or emery cloth can be used to remove traces of the former gasket, but we’ve found that a scraper works better, particularly in tight spaces. You can get the necessary tools in your local Home Depot or off of Amazon.
What You Need
- Exhaust manifold gasket
- Ratchet and socket set
- Penetrating oil
- Torque wrench
- Jack and jack stands
- Repair manual
Steps To Repairing An Exhaust Manifold
- Detach the negative battery cable. The engine must be cooled down.
- Engage the parking brake. Raise the front of the car using a jack and place it on jack stands.
- Remove any heat shields or engine cover with the ratchet and sockets to gain access to the bolts of the exhaust manifold. It might be easier from under the vehicle depending on the engine.
- Check to see if any other parts are disconnected, like the dipstick tube or EGR valve intake pipe. Remove the bolts and set them aside.
- Spritz penetrating oil over the exhaust manifold bolts.
- Spray oil over the boils linking the exhaust pipe flange and the exhaust manifold collector. Let it soak for 10 minutes.
- Apply slow but steady pressure to the bolts of the exhaust manifold using the ratchet. The bolt should pop without too much force. However, if it doesn’t give, spritz a little penetrating oil and hit it a few times with a hammer. The oil can penetrate rust better thanks to the impact vibration.
- Take out all the bolts, aside from the one on the cylinder head, and then remove the bolts located at the collector. Place one hand on the exhaust manifold before removing the last bolt to lift the manifold.
- Discard the old gasket. Spray heavy-duty degreaser on the exhaust manifold. Once dry, check the manifold for cracks or carbon buildup, if any. Clean the area around it if there is carbon and change if you see cracks.
- Spray over the cylinder head too, prepping the area where the new gasket will be fitted. Use the towel to scrub and remove any deposits.
- For this step, wear gloves beforehand. Place the new replacement gasket on the studs of the cylinder head.
- Place the cleaned manifold in its original position. Change the bolts and secure them tightly.
- Torque the bolts to their specific specs as mentioned in the repair manual.
- The assembly now is the reverse of the extraction. Recheck the torque after a week of driving to prevent the bolts from slipping out later.
Exhaust Manifold Repair Cost: How To Save Money
Many people like to repair themselves to save money. You can definitely try to perform a repair on an exhaust manifold but only if you’re confident in your skills. If the problem is caught early on and is not as severe, you can get away with basic skills and the right amount of research.
At the later stages of a leaking exhaust manifold, the damage could be too severe for a regular person to handle. The right tools combined with prior experience and knowledge are required to do a good job, and only a professional boasts these.
Moreover, you may not be able to properly diagnose the actual cause of the damaged exhaust manifold, making it hard to understand where you should start the repairing process.
One other option is to compare prices offered by various mechanics to get the best deal. You can compare parts costs and labor costs from suppliers and local stores in your area to save a few coins and still get the required repairs done at a good price.
Typically, shops refer to a parts and labor guide to calculate how many hours of labor should be charged for any repair. Repairs usually last between two to three hours. An independent shop would charge you about $80 to $90 per hour, so that brings your labor costs to $160 to $270 for the 2-3 hours.
The labor rate is generally higher at a dealership, with an average of $110 an hour. After two or three hours, you have to pay between $220 and $330. There are no labor costs involved if you decide to do the repair yourself, and you can also learn some valuable technical skills in the world of automobiles.
The exhaust manifold gasket cost will vary depending on the model, make, and year of the car as well as the number of cylinders the engine has. On a 2000 Chevrolet Impala, for instance, you can expect to pay about $20 to $30 at your local parts retailer for just the gasket. The price increases to around $50 if you choose to get it from a dealership, but the aftermarket gasket works fine.
With the prices mentioned above, the repair can be done for the low price of $18 if you do it yourself. Alternatively, your total rounds up to $400 if you get it done from a dealership.
There are a few kinds of cars that have introduced different exhaust manifold repair costs to the market. For instance, the labor costs of a Ford F-Series come to $270 to $350, while the parts can be bought for anywhere between $200 to $340. Round it all up, the total cost to replace a cracked exhaust manifold for a Ford F-Series pickup ranges between $470 to $690.
The lowest repair costs for a cracked exhaust manifold is for the Honda Accord where the charges are about $90 to $115. The parts run for around $260 to $460 and the total rings up to $350 to $590.
The Honda Civic has one of the highest costs in regards to exhaust manifold repair, with the parts alone being $580 to $850. Combine that with the labor costs of around $270 to $350 and you can end up paying $800 to $1000 for one repair of the car. The high labor costs can be attributed to the complexity of the problem. It usually takes a professional several hours to fix.
The costs will depend vastly on the kind of car you have and whether you brought it to your local mechanic or dealership before.
Exhaust Manifold Repair – Conclusion
The exhaust system of your vehicle is a big deal, so it should go without saying that you must never ignore it. The symptoms can combine with each other and manifest in multiple ways. There are easy steps outlined that can help you find the fault and conduct exhaust manifold repair. The more you know about your vehicle, the simpler it will be for you to maintain it.
These tools have been tried and tested by our team, they are ideal for fixing your car at home.