At first glance, the flex pipe doesn’t seem special aside from being more flexible than other pipes in the exhaust system.
But like any other exhaust part, it contributes a lot to how well your ride performs on the road. When a flex pipe wears out or breaks down, it can cause serious problems for your vehicle. Read on to learn about its role in the exhaust system and the common signs of failure you should watch for.
What is a Flex Pipe?
The flex pipe is a type of tubing that connects the engine and exhaust system. Also called the exhaust flex pipe, it is made from strong yet malleable materials like steel alloy.
Aside from connecting the engine and exhaust system and transporting exhaust gases, the flex pipe absorbs the vibrations produced by your vehicle when you’re driving. By keeping the exhaust system from shaking too much, the pipe helps other exhaust parts last longer.
What Are the Symptoms of a Bad Flex Pipe?
Like any other piece of metal, even though a flex pipe is made to flex for the life of the vehicle, flex pipes can fail over time due to continual flexing. While flex pipes can handle vibrations much better than other exhaust pipes, years of absorbing every bump and shake can make them crack. They can also get damaged when your vehicle bottoms out to the point that the pipes hit or scrape against the road surface.
Damaged and worn-out flex pipes are prone to exhaust leaks. The exhaust gases produced by the engine can escape through cracks in the pipe.
You may also hear loud noises coming from leaky flex pipes. Your engine will sound louder than normal because the sounds produced by its operation escape through the cracked pipe. A bad pipe may also make hissing or tapping sounds that become louder when you step on the gas pedal.
Severe cracks can leave the flex pipe hanging from underneath your vehicle. If it dangles low enough to touch the road surface, it can make a racket.
Can You Drive with a Bad Flex Pipe?
Yes, you technically can, but that doesn’t mean you should. A cracked or leaky pipe not only makes driving harder but it may also damage other parts of the vehicle. Also, if you drive your vehicle when it has a hanging flex pipe, the damaged part will noisily drag across the road surface. It can even throw out sparks that may ignite fuel vapor or fragments and can damage your vehicle’s underside.
How to Fix a Flex Pipe
You can replace a bad flex pipe by yourself if you have the tools, parts, and skills required for the repair job. A DIY replacement and installation can save you the considerable cost of paying a professional technician for their labor.
On average, it takes an experienced mechanic less than an hour to replace a faulty flex pipe. A direct-fit flex product speeds up the process. You can swap out the old exhaust part for the new exhaust flex pipe without modifying anything.
If you lack the tools or skill to install a new flex pipe on your own, it’s best to let your mechanic handle the job.
Shopping for Replacement Flex Pipes
Be selective. There are numerous flex pipe products available today, and not all of them are equal. To find the best pipes for your ride, you must first pay attention to your stock parts’ dimensions.
Flex pipes come in different sizes that may or may not prove compatible with your vehicle’s exhaust system. Always start your search by getting the inlet diameter and length of your old pipe and comparing them with the dimensions of a potential replacement. The new exhaust flex pipes should precisely match your stock parts for maximum efficiency and easy installation.
You must also take note of your replacements’ material. Most flex pipes are made of steel alloy. Forged steel is sturdy, but it’s also heavy and potentially vulnerable to corrosion. Meanwhile, stainless steel offers superior protection against rust, while aluminized steel exhaust flex pipes save weight. Determine which material best suits your needs.
A Closer Look at the Flex Pipe
The flex pipe has an extremely important function most people don’t consider. Since every engine shifts on its mounts as it applies torque to the driveline through the transmission or transaxle, the movement of the engine in relation to other components requires flexible power steering and A/C hoses to allow for engine movement. If stiff, unyielding piping was used, said piping would soon fracture and too much engine vibration would be heard and felt by the passenger.
The same is true of the engine’s exhaust connection. The exhaust is typically mounted on flexible hangers, but as the engine shifts while applying torque, a flexible joint is needed between the engine and the exhaust.
This is a minimal shift on linear mounted engines, although it’s still an issue. Front-wheel drive platforms with transversely mounted engines are far more susceptible to engine movement while driving because the engine tends to “roll” backward and forward as torque is applied, making some kind of flexible joint vitally necessary for the exhaust system to remain sealed and to prevent noise, vibration, and harshness that would be transmitted to the passenger compartment with no flexible joint.
This need for a flex joint can be satisfied with ball-shaped, graphite coated gaskets where the header pipe connects to the exhaust manifold. Many front-wheel drive vehicles used this method of dealing with isolating engine movement from the exhaust while still providing a perfect seal between the two. But today’s vehicles more commonly use a flex joint, either right where the header pipe connects to the manifold, or slightly farther back, but the flex pipe is always near the engine.
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