Did you hear that?
That sounded like a rattle.
It is pretty unlikely that it is a snake, so if your vehicle starts making rattling sounds, there’s clearly an issue that needs to be dealt with.
What causes a car to make a rattling noise when accelerating? The most likely culprits include the following:
- Broken Heat Shield
- Damaged Engine Mounts
- Valve Train Issues
- Transmission Problems
- Worn Exhaust Components
Thankfully, this guide will explore each of the above reasons in detail. Not only that, but I will also address how to fix them.
Let’s get started right away!
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Does Your Car Rattle When Accelerating? 5 Possible Causes And How To Fix Them
Cause #1 – Broken Heat Shield
Heat shields are metal guards that surround various parts of the exhaust system, keeping your car safe from the heat it puts out.
One reason heat shields tend to break is due to their close to the ground location. Often around the gas tank, muffler, exhaust piping, and exhaust manifold. This not only leaves them exposed to debris but moisture as well, which means they will likely develop problems with rust.
You guessed it – if the damage is severe enough, it can cause your car to make a rattling sound when accelerating.
The reason they do so while accelerating is due to more strain being put on the engine. The harder it works, the more air flows through the exhaust, which is where the bulk of the heat shields in your car is placed.
How To Fix
According to my many years of experience in this field, heat shields are quick and affordable to repair unless they have sustained real damage.
If you do have to replace one, you’ll likely spend between $250-$300. Otherwise, having it spot-welded at a local shop should do the trick.
Cause #2 – Damaged Engine Mounts
If you didn’t already know, the average car engine weighs about 300 lbs, and the engine mounts are what hold it securely in place.
They’re made of rubber and metal, so as you may have guessed, if they’re broken, there’s nothing to stop the engine from moving around.
This means metal-on-metal contact, which can cause your car to make a rattling noise while accelerating due to the added workload (as well as momentum).
If left alone, there will likely be more than just a rattle to worry about. Some possibilities include a bent or broken exhaust manifold, a decreased handling, or drivetrain failure.
How To Fix
The good news is that broken or damaged engine mounts are not difficult to resolve. While you can always crawl under your car and check yourself, it might be easier to have a licensed professional put it on a lift and take a look.
They should be able to replace the worn/broken mount for between $200-$500.
Cause #3 – Valve Train Issues
If your car makes a rattling noise that sounds like glass bottles clinking together, it’s likely a valve train issue.
This system is in charge of the operation of the intake and exhaust valves. If any of these are stuck or worn (including the hydraulic lifters), it can cause premature ignition inside the combustion chambers.
This is often referred to as carbon rap, and it’s usually caused by dirty oil or filling your car with gas that is not the correct octane level.
How To Fix
If it is the valve train (located on the top of the engine), you should first check what shape your oil is in. If it’s dirty, an oil change may be all that’s needed.
It may also be that your engine requires a higher-octane fuel, which will show in your owner’s manual. If it’s designed for 95 and you’re putting in 89, engine performance will suffer and possibly create a rattling sound.
Cause #4 – Transmission Problems
A lot goes on inside a transmission, and as with most engine components, if it’s not receiving enough lubrication, it won’t be able to operate correctly.
Transmission fluid forms a thin layer between the moving parts so they don’t rub directly against each other. Without enough of it, they will, which can cause your car to rattle while accelerating.
Ignoring a transmission that’s low on fluid will eventually lead to a costly repair bill. As metal grinds on metal, it will cause the gears to wear down, and when they become unusable, you’ll have to rebuild or replace the transmission.
How To Fix
Thankfully, if you routinely change your transmission fluid every 30,000-60,000 miles, you should never have an issue with it. Regardless, if it is your tranny, the first thing you should do is check the fluid levels. If it’s low, then you will need to add more.
For more information on tranny fluid, as well as the costs associated with having it replaced, check out our previous article here.
Cause #5 – Worn Exhaust Components
There are a lot of different components inside an exhaust system that can cause your car to rattle when accelerating.
Some of these include:
- Loose or broken pipe connection
- Rusty muffler
- Blown exhaust gasket
- Broke or disconnected exhaust hanger
- Catalytic converter failure
- Faulty active exhaust
Ignoring any of these can adversely affect the rest of the system. Not only that, but they can also cause a decrease in performance and fuel economy.
How To Fix
The first step is to figure out which part of the system is having an issue. You can crawl under your vehicle and inspect it for damage. Just be sure to let it cool down first if you’ve recently been driving.
You can also use your hands to “shake” the system, listening for any rattling noises.
If you don’t feel comfortable doing this, taking your car to a licensed mechanic may be your best bet. If they don’t notice any visible issues, they can also perform a pressure test to tell if there’s a leak somewhere.
Don’t Lose The Rattle Battle – Instead, Get Rid Of It
A car rattling when accelerating will eventually become more than just an annoyance. As you may have noticed from the above car rattling causes, many of them stem from a lack of proper maintenance.
For this reason, be sure to take care of your car, and if it does start rattling, handle it before it gets worse.