What Is That Engine Knocking Sound?
What is That Engine Knocking Sound?
You’re driving your truck on the freeway when you hear a rattle increasing in pitch and a bad vibration form, then your own wheel rolls past you. Your engine’s constant drone suddenly gives way to a loud roar and the Check Engine light pops on. You’re cranking your engine over when it sounds like marbles caught in a blender.
Out of Place Car Noises
In life, the two constants are death and taxes. In car ownership, the two constants are maintenance and repairs. The two are inescapable if you plan on keeping your car for any length of time. And despite your best attempts at routine services and fluid changes, problems can still happen. When you car starts making noises that aren't normal, it's an indication that something is going wrong and it's time for maintenance or repair.
Noises like these are clues into problems, both large and small, that can happen to anybody, regardless if your car is new or old. Sometimes a car makes a loud noise on acceleration or you might find your car making squealing noises when you start it. Some of these noises are minor repairs while others have the potential to ruin your budgeting for the year. Or in worst case scenarios, your car could degrade into a state where insurance declares your car a total loss. No one wants that, but if that happens selling your totaled caris probably your best bet. So here are the top potential issues a car can go through.
Did You Know?
Car knocking sounds may be the infamous spark plug knock, which could lead to serious engine damage and expensive repairs. When your engine knocks it's likely you will soon face high repair costs.
In this case, selling your car is preferable to spending so much on parts and labor. CarBrain makes fair market offers on cars in any condition, running or non-running. See how much you can get for your damaged car now.
1. Engine Knocking
It can be an issue as small as bad-quality fuel that causes an engine knocking sound. You can’t ignore it, though, because it could be much more serious. Engine knocking noises can also be caused by:
- Connecting rod bearing failure
- Engine timing belt or chain issues
- Low oil pressure
- Valve lifter failure
- Emissions-related blockages
- And more.
A rod knock sound is one of the most serious problems. If engine noise seems to be from the bottom of the engine, it’s likely from damage to the connecting rod bearings. Another engine knock sound that’s become commonplace with variable valve timing systems comes from the top end of the engine. If left unattended you could seize your engine.
An engine knock fix could be anything from a few hundred to several thousand dollars. For example, engine knock related to poor octane content in your fuel may only require refueling your tank. On the other hand, a rod knock requiring a short block engine replacement could easily cost $3,000 to $4,500. Your vehicle may not be worth the cost of the repairs.
2. Brake Making Noise
The speed limit decreases, so you press your brakes. If you feel a clunk-clunk-clunk in the brake pedal, you’ll probably want to get off the highway and get your car fixed. Clunking when you brake can be caused by one of several things like a seized brake caliper, an extremely loose wheel bearing, or even worn out ball joints or steering components.
When you have a clunk, that means there is play where there should not be. A seized caliper means your brakes aren’t working as effectively as they could. If you have a loose wheel bearing or hub, your wheel is flopping side to side instead of moving true in the direction you have steered your car. The same goes with worn ball joints and steering components.
Clunking when you press your brakes is an indicator of a safety item. It might be a simple brake pad replacement or a complete suspension and steering system overhaul. If you hear grinding brake noise, scraping brake noise, or clunking you should get your brakes inspected right away.
3. Flapping Noise while Driving
If you’ve reached highway speeds and start to hear a flapping noise, you know something is loose on your car somewhere. It could just be broken fasteners on a plastic shield under your engine or a wheel liner that’s come loose. Or, it could be more serious like your bumper cover flapping in the wind.
Usually, it’s some form of trim that isn’t properly attached anymore. If that’s the case, you need to ask why it has come loose. Is there other damage of which you aren’t aware?
A flapping sound from under the hood is commonly the fan belt starting to fray. It could also be something interfering with the fan blades - something like a block heater cord.
4. Car Grinding Noise when Accelerating
Like nails on a chalkboard a grinding noise doesn’t feel good. If your car makes noise when accelerating, it can be a problem like a worn-out clutch disc or wheel bearing. Grinding isn’t always the first indicator of a problem, however. If you notice your car making a whining noise when accelerating, addressing it early can prevent it from becoming a grind.
A similar concern to grinding is if your car makes a clicking noise when accelerating and turning a corner at high speeds. That can be a clutch problem in a manual transmission, an automatic transmission issue, a worn u-joint or CV joint, or something in the brakes, suspension or steering. Leave it alone long enough and it’s going to get worse.
5. Knocking Noise Under a Car when Going Over Bumps
Looseness in your suspension usually cause a knocking noise when you go over bumpy roads or potholes. It’s possible your struts or shocks are leaked out, your stabilizer links or sway bar bushings are worn, or your control arms are loose.
Knocking noises are early indicators, telling you to get it addressed before serious failure occurs. When suspension components let go completely, you lose control of your car. That’s when accidents happen.
6. Car Making Rattling Noise Over Rough Roads
In your vehicle’s lifetime, expect suspension or steering repairs due to normal wear. A car making squeaking noises often develops rattling as the wear gets worse. Rattling is commonly caused by stabilizer links or looseness in ball joints.
Rattling can also be from a loose exhaust pipe or brake pads that are moving around in the caliper. Repairs can be as small as tightening bolts or replacing clips to hundreds of dollars in suspension repairs.
7. Clunking Noise When Starting the Car
If you cringe before you turn your car key in the ignition, it’s not a good sign. A car making noise when starting often indicates either a starter failure or broken teeth on your transmission’s flexplate.
Some cars require several hours to replace the starter and hundreds of dollars for a replacement part. If your car needs a new flexplate, it’s a much bigger issue. The transmission must come out to replace the flexplate, and there’s probably additional parts your car will need while the job is being completed. It’s $1,500 and up to replace a flexplate in most vehicles.
8. Rattling in a Car Under the Hood
If your car is running but you’re not driving and you hear a rattle, you might be puzzled. There are a couple of items that could cause the issue, though, even when you’re not driving. Loose exhaust or a rusted exhaust heat shield can vibrate, causing quite a racket. It’s not nearly as devastating as a failing catalytic converter, though…
If you have a car making a rattling noise when accelerating, your catalytic converter is probably on the outs. When your cat starts rattling inside, it’s only a matter of time before it causes a blockage that makes your engine run poorly.
Catalytic converters are one of the most expensive exhaust components. It’s not uncommon for your catalytic converter replacement to cost more than $1,000, and there’s usually more work that needs to go along with that.
9. Car Grinding Noise Under the Hood
You might not notice your car making noise when driving. But when your engine is idling, you may hear a scraping noise from the front of your car. The rotating parts all attached to the front of your engine have bearings to allow them to move smoothly. When those bearings wear out, they cause that rough grinding or scraping noise.
It could be an alternator, an A/C compressor clutch, idler pulley, water pump, or belt tensioner that needs to be replaced. It may even be more than one part that needs to be changed.
10. Crunching Noise At Low Speeds
Whether you find your car making noise when accelerating or just idling a through a parking lot, you shouldn’t ignore it. Crunching noises are one of the issues that can leave you stranded. When you have a RWD, AWD, or 4WD vehicle, the rear differential and the transfer case can be failing. Gears don’t mesh together properly or internal bearings are piling up.
If your car makes noise when accelerating at low speed, you’ll want to get it checked out sooner rather than later. Make sure there’s room on your credit card because these types of repairs aren’t exactly cheap…
11. Engine Smoking or Hissing
A plume of steam or smoke could very well accompany a hissing noise from your engine. That’s the sound of coolant escaping, usually related to an overheating condition. That’s bad news for any engine.
The most common problems related to hissing noises are a blown cylinder head gasket, a failing water pump, or a leaking radiator. But if your engine has already overheated, you could be in for a pretty severe repair bill. In the case of a blown engine, you should probably sell your blown engine car.
12. Clicking Noise When Turning
If you discover your car making noise when turning, there are several things it could be. If your car is making a clicking noise, it might be a CV joint failing on an axle shaft or an internal transmission issue. It could also be early wear in the steering system like an inner tie rod on your steering gear.
If your car is making a clicking noise when turning, there’s a good chance it’s safety related. Steering and axle issues can leave you stranded or cause an accident. Transmission problems and steering gear replacement are expensive, and your car may not be worth the time, effort, and cost.
13. Knocking Noise when Accelerating
The stress on your car while you accelerate can draw out noises you wouldn’t otherwise hear. If your car makes a rattling noise when accelerating, it could be your engine is worn out with low oil pressure or piston slap. If your car makes a humming noise when accelerating, it could be an issue with a failing wheel hub or a drivetrain concern.
If you find your car is making a loud noise when accelerating, no matter if it’s a pop, clunk, bang, rattle, or ping, you need to get it looked after. Engine repairs are expensive no matter what make or model you drive.
Your engine isnt the same anymore after its experienced noises of any kind and its a strain on your wallet and calendar. Running from hundreds to several thousands of dollars and at times spanning weeks to repair, you might not want to deal with the repairs.
If you are curious about even more problems an engine can experience, check out our guide on blown engines to learn more.
With CarBrain, we can alleviate that stress. We’ll make you a guaranteed offer for your car in its current condition. All you have to do is accept our offer and we’ll send someone to pick up your car. You’ll receive money in your pocket on the spot and your problem car will be gone! Find out how much you can get for your car right now.