How to Diagnose & Fix a Car That Rattles When You Accelerate

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Plus, causes and fixes for a rattling noise when braking or idling
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If you’re noticing odd rattling noises (or you feel a rattling vibration in your steering wheel) when you accelerate, you probably have a problem with your engine or suspension. There are a variety of potential causes that can cause rattling, and we'll explain all of them as well as the repairs you'll need to fix the issue.

What Causes a Rattling Acceleration Noise?

A vehicle that rattles during acceleration may be low on oil, have a loose serpentine belt, or damage to its flywheel or flexplate. A damaged engine mount or alternator can also trigger rattling when you hit the gas. See a mechanic to have your vehicle diagnosed and repaired if your vehicle rattles when you accelerate.

Section 1 of 3:

Rattling When Accelerating: Causes & Fixes

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  1. Engine oil is responsible for keeping the engine components lubricated and cool, but if you’re low on oil the engine’s moving parts will grind and wear on one another as you drive. The faster you go, the more heat this friction produces. Eventually, that friction will create a rattling sensation. [1]
    • Other Symptoms: The problem is worse when the engine is hot, your engine runs hot, the check engine light comes on, the check oil light comes on, or you see smoke coming out of the engine bay.
    • The Fix: Look under your engine bay for puddles and check your dipstick . If you just happen to be low on oil, add more. If you do have a leak, see a mechanic to have the leak repaired and get an oil change.
    • Estimated Cost: If you do need a mechanic to patch a leak, expect to spend $100-500 depending on which gasket or valve needs to be repaired.
  2. The serpentine belt, also known as a timing belt, is the rubber belt that runs around the pulleys on the side of your engine. It’s responsible for synchronizing the valves, pistons, and crankshaft so that the combustion in the pistons occurs in the proper sequence. If the belt is loose, the engine won’t operate correctly and it could cause the engine to shake and rattle. [2]
    • Other Symptoms: Your engine misfires, your car starts to seize or stall once you get up to higher speeds, you get poor fuel mileage, or you see fumes and smoke coming from the engine bay.
    • The Fix: If the belt has lost its texture or it’s old, it probably just needs to be replaced , which is a DIY job if you’re handy. Otherwise, see a mechanic to have them readjust the chain tensioner or replace the belt.
    • Estimated Cost: This shouldn’t run more than $50-250 if you have a mechanic do it.
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  3. The flywheel is a disc that helps rotate the engine when you start the car. After starting, the flywheel is responsible for smoothing the engine out and maintaining rotational momentum when you shift gears. If the flywheel is cracked, it can cause all kinds of stutters and jumps when you accelerate that feel like rattling in the steering wheel. [3]
    • Other Symptoms: You smell something burning, the shaking gets worse when your transmission tries to shift gears, you struggle to start the engine, and you have trouble operating the clutch.
    • The Fix: See a mechanic to have the flywheel inspected and repaired.
    • Estimated Cost: Accessing the flywheel is relatively complex because it’s usually situated in between the transmission and engine. As a result, it can run $800-2,000 to fix a flywheel.
  4. In automatic vehicles, the flexplate serves the same purpose as the flywheel. However, it also joins the torque converter to the transmission to help maintain rotational power in the engine. A broken or misaligned flexplate will cause your engine and transmission to rattle when you accelerate. [4]
    • Other Symptoms: Your entire vehicle vibrates the faster you go, you hear scratching noises, your engine performance is poor, and your vehicle struggles to shift gears.
    • The Fix: Visit a professional mechanic for flexplate repairs.
    • Estimated Cost: Like flywheel issues, flexplate repairs require a lot of effort. Expect to spend $1,000-3,000 repairing a cracked or damaged flexplate.
  5. The engine mount is the frame that holds the engine up in your vehicle’s engine bay. If part of the engine mount cracks or breaks, the engine will shake and vibrate when you drive. The faster you go, the more vibration you’ll notice. [5]
    • Other Symptoms: The check engine light comes on, you hear odd noises coming from the engine bay, the ride generally feels rough, and you keep spurring oil leaks.
    • The Fix: The frame needs to be repaired but this requires a pro. See a mechanic. They’ll remove the engine and fix the frame.
    • Estimated Cost: You’ll likely spend $200-500 fixing a cracked mount.
  6. Your exhaust system is responsible for safely directing all of the noxious fumes created by your engine out of the vehicle. If one of the exhaust pipes is loose or a clamp holding a pipe in place is broken it can create rattling noises when you drive as the metal components bang against the chassis. [6]
    • Other Symptoms: You may not have any. If the broken component is causing an emissions leak, you may notice nasty odors or have a check engine light pop on, though.
    • The Fix: If you can get under your vehicle, gently wiggle the pipes and components to look for loose connections and tighten them as needed. If you can’t get under the vehicle, just have a mechanic inspect it.
    • Estimated Cost: It depends on what’s loose, but this shouldn’t run more than $100-200 most of the time.
  7. A bad catalytic converter can cause rattling noises, although you’re unlikely to feel any kind of rattling in your vehicle. The catalytic converter absorbs all of the noxious emissions, but if it’s failing, damaged, or clogged, the emissions can build up in the converter and trigger and kinds of weird noises. [7]
    • Other Symptoms: You smell rotten eggs, the rattling is present when you idle, your check engine light comes on, and you see smoke coming from the back of the vehicle.
    • The Fix: You likely need a new catalytic converter. See a professional mechanic.
    • Estimated Cost: Catalytic converters are expensive unfortunately, so you may need to spend up to $3,000 on a new converter.
  8. Your vehicle has multiple heat shields. They’re basically panels that surround components that get extremely hot to prevent them from damaging other components or starting fires. If a heat shield is loose, it may bang against the component it’s protecting and cause a rattling noise. [8]
    • Other Symptoms: In fringe cases, your engine may overheat. You’re unlikely to notice any other symptoms, though.
    • The Fix: Heat shields are essential for the safety of your vehicle, so see a professional mechanic to ensure any loose heat shields are safely secured.
    • Estimated Cost: This shouldn’t cost more than $100-150 if a heat shield is just loose. If it needs to be replaced, it may run $150-300.
  9. You’re more likely to notice other issues beyond rattling feelings and noises when you accelerate if the alternator is bad, but this will certainly trigger rattling. The alternator is responsible for keeping your vehicle’s electrical on after the engine starts, so if your power starts to diminish you may feel and hear rattling as your engine struggles to help keep your car running. [9]
    • Other Symptoms: You notice odd electrical issues, the engine stalls, you have trouble keeping the vehicle running for long periods of time, and the dash lights randomly dim.
    • The Fix: See a mechanic to have the alternator repaired or replaced.
    • Estimated Cost: Expect to pay $700-900 for a new alternator.
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Section 2 of 3:

Rattling When Braking: Causes & Fixes

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  1. If your brake pads are old and worn down, your vehicle may begin to rattle when you hit the brakes. This is a major sign you’re dangerously close to brake failure, so do not continue to drive if you’re struggling to maintain control of the car as you brake. [10]
    • Other Symptoms: You hear screeching noises when you brake, you have to press harder on the brakes than normal, and you have trouble slowing down.
    • The Fix: You need new brake pads. See a professional mechanic.
    • Estimated Cost: You’ll probably spend $100-200 per axle.
  2. The suspension refers to the frame, joints, springs, and shocks that sit in between the wheels and the chassis of the vehicle. It helps your tires maintain even contact with the road and absorbs shocks from bumps and potholes. If a component of the suspension is damaged, you may notice the car rattles when you brake. [11]
    • Other Symptoms: You hear creaking noises (especially when you turn), your ride is rougher than normal, and you find it harder to drive in the rain.
    • The Fix: See a mechanic to have the suspension inspected and fixed as needed.
    • Estimated Cost: There are a lot of different components in your suspension, so it really depends on which specific part is the issue. Replacing a single strut may only run $200, while new CV joints may run up to $1,200.
  3. This is a relatively rare source of rattling when you brake, but misshapen or bald tires can slide or skid and cause your vehicle to rattle when you brake. However, this is unlikely unless your tires aren’t all the same age or you haven’t replaced them in years. [12]
    • Other Symptoms: Your brakes feel less sticky and your vehicle slides or bumps more often than it normally would.
    • The Fix: The damaged tire needs to replaced. To keep things even, you likely want to replace all of your tires .
    • Estimated Cost: Expect to pay around $600 for a new set of tires.
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Section 3 of 3:

Rattling When Idling: Causes & Fixes

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  1. The hydraulic valve lifter is responsible for opening and closing the valves in your engine so that air can enter the pistons. If the hydraulic valve lifters aren’t working properly, your engine may shake and rattle as soon as the car starts. This rattling may smooth out as you drive, though. [13]
    • Other Symptoms: A loud ticking or clicking noise coming from your engine bay, poor vehicle performance, bad gas mileage, and the check engine light kicks on.
    • The Fix: The lifters need to be replaced and recalibrated. See a professional automotive mechanic.
    • Estimated Cost: The valve lifters can run a little pricey depending on your make and model. You’ll likely spend $1,000-2,500 on new lifters.
  2. Physical damage to your engine’s core mechanical components can trigger all kinds of engine shaking when you start the car. This kind of physical damage is relatively rare, but if your car’s engine is very old or you recently rebuilt it, a bent or damaged piston could be the source of your woes. [14]
    • Other Symptoms: Your check engine light comes on, your gas mileage is bad, your engine smokes, and the rattling in your engine bay causes extremely loud slapping sounds.
    • The Fix: Visit a mechanic to have the engine piston replaced.
    • Estimated Cost: Anywhere from $1,000-4,000 depending on the engine and the scope of the damage.
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      References

      1. ↑ https://static.nhtsa.gov/odi/tsbs/2021/MC-10203724-0001.pdf
      2. ↑ https://www.landroverpalmbeach.com/parts/parts-tips/what-is-a-serpentine-belt/
      3. ↑ https://www.cars.com/articles/what-is-a-flywheel-441463/
      4. ↑ https://www.cars.com/articles/what-is-a-flywheel-441463/
      5. ↑ https://www.gmtrubber.com/5-signs-need-replace-engine-mounts/
      6. ↑ https://www.autobytel.com/question-why-does-my-exhaust-rattle-when-accelerating
      7. ↑ https://www.corsaperformance.com/blogs/news/signs-of-a-bad-catalytic-converter
      8. ↑ https://www.autobytel.com/question-why-does-my-exhaust-rattle-when-accelerating
      9. ↑ https://heartautocare.com/10-clear-signs-of-bad-alternator-dont-ignore-these-symptoms/
      1. ↑ https://www.autozone.com/diy/brakes/worn-out-brake-pads-symptoms
      2. ↑ https://www.spotonvehicleinspections.com.au/suspension-damage-estimation/
      3. ↑ https://evanstire.com/8-sounds-indicate-car-troubles/
      4. ↑ https://www.carparts.com/blog/bad-lifter-symptoms-noise-replacement-cost-and-more/
      5. ↑ https://www.dubizzle.com/blog/cars/engine-piston-damage/

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