Car makes knocking sound

My car runs but makes a horrible knocking sound like the piston wants to come through the block. I was told that I blew a valve or had a valve-related issue. And when it runs too long, it overheats but maintains oil levels.
Experienced mechanics share their insights in answering this question :
A valve train issue usually sounds more like a tapping sound similar to a pencil tapping quickly on a desk. Depending on the engine, a vehicle with a 4 cylinder engine can have as many as 16 valves. If several of those have problems, it sounds like a bunch of pencils hitting the desk. When it is something in the "bottom end" of an engine, meaning piston, crankshaft, rod or mains, the knock is like a carpenter hitting the side of the engine with a hammer. This sounds more like what you are describing. A lower engine knock is very serious. It requires at the minimum opening up the engine to replace bearings if no other damage has been done. Depending on mileage, it might be best to rebuild the engine altogether. Seek help from a qualified mechanic that can go and inspect the vehicle’s knocking sound, such as one from YourMechanic. They will be able to better determine what direction you should go.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Knocking occurs when fuel burns unevenly in your engine`s cylinders. When cylinders have the correct balance of air and fuel, fuel will burn in small, regulated pockets instead of all at once. (Think sparklers, not fireworks.)
The spontaneous ignition of air/fuel inside the cylinders is a common source of engine knock. While the description of the sound may differ, the circumstances under which it occurs are often the same – low-speed, high-torque conditions common when you`re accelerating.
If you hear a light knocking or pounding sound, the noise can usually be traced back to your connecting rods. This sound is often most noticeable when the engine is at an even rpm–not accelerating or decelerating–and is often caused by a worn bearing or crankpin, misaligned connecting rod, or lack of oil.
An engine knock can usually be attributed to a detonation problem, which is why the knocks shouldn`t be ignored. Bad engine detonation can cause catastrophic engine failure if the problem is left unchecked. Techway Automotive can inspect your engine and find the cause of your engine knock.
If you start to notice rod knock, this isn`t a problem that will just resolve itself—you must take immediate action and replace the rod bearing while also fixing any other parts associated with the sound. If you do not take action quickly enough, you might need to replace the engine entirely.
Engine knock isn`t always the easiest car problem to repair. Here are a few of the most common solutions to knocking issues. Timing belt replacement: Most smaller cars, including most four-cylinder sedans, will use a rubber belt to regulate and control your engine`s timing.
It`s easy to misdiagnose the cause of engine knock, so you might have to pay a visit to your mechanic. Each of the engine knock causes on the previous page has a specific cure, and most of these fixes are simple. However, it doesn`t guarantee the knock will go away.
FAULTY KNOCK SENSOR: SYMPTOMS

Engine warning light comes on. Error code is stored. Reduced engine power. Increased fuel consumption.

If you do experience a knocking sound coming from your engine, it`s important to stop driving immediately and have a qualified mechanic diagnose and repair the problem. Allowing rod knock to continue unchecked can lead to serious damage to your engine and should be taken seriously.
If you start to notice rod knock, this isn`t a problem that will just resolve itself—you must take immediate action and replace the rod bearing while also fixing any other parts associated with the sound. If you do not take action quickly enough, you might need to replace the engine entirely.
Once an engine starts to knock, the rod can fracture without warning. It could be the next time you start it in your driveway, or it could keep going for six months. Eventually though, the engine will blow and you`ll be stranded somewhere.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Car has developed a knocking sound
ANSWER : Though your vehicle’s mileage is extremely low to have this sort of issue, the most likely cause is a rod knock from the engine. Generally, this happens when engines run very low on oil or high mileage. The most likely time to have problems with new vehicles is within the first few thousand miles, since this when assembly line issues will begin to surface. If you need a second opinion on the car, a technician from YourMechanic can come to your location to diagnose the car noise and let you know what repairs are appropriate.

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Car sounds like golf cart when revving and braking; also leaking fluid; sound fades as car warms up
ANSWER : Hello,
There are a number of things that could make an engine noisy when starting up. Depending on the specific type of sound you are referring to, this will determine how to properly diagnose. If there is a bit of a hissing sound, this may be a sign of a vacuum leak. If this is more of a shrieking sound, this may be a sign of a worn out or out of adjustment serpentine belt. If there is a bit of a howling or growling sound, this may be a sign of a worn out or low on fluid power steering pump. A rattling or pinging sound may be caused by an ignition problem. An engine can ping (or knock) due to an improper combustion process. A "spark knock" is the result of combustion occurring too early. Early combustion can occur from carbon buildup inside the combustion chamber, a lean air/fuel mixture, and advanced ignition timing (spark plug firing too soon). A clattering type sound may be a result of improper lubrication in the valve train which could be a more serious problem and should be addressed as soon as possible. I would suggest having an expert from YourMechanic come to your location to diagnose and inspect your vehicle to ensure everything is in proper working order.

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Oil leaking from under car and "remote control car" sound when car is first started for a few minutes until it warm up.
ANSWER : Hello,
There are a number of things that could make an engine noisy when starting up. Depending on the specific type of sound you are referring to, this will determine how to properly diagnose. If there is a bit of a hissing sound, this may be a sign of a vacuum leak. If this is more of a shrieking sound, this may be a sign of a worn out or out of adjustment serpentine belt. If there is a bit of a howling or growling sound, this may be a sign of a worn out or low on fluid power steering pump. A rattling or pinging sound may be caused by an ignition problem. An engine can ping (or knock) due to an improper combustion process. A "spark knock" is the result of combustion occurring too early. Early combustion can occur from carbon buildup inside the combustion chamber, a lean air/fuel mixture, and advanced ignition timing (spark plug firing too soon). A clattering type sound may be a result of improper lubrication in the valve train which could be a more serious problem and should be addressed as soon as possible. I would suggest having an expert from YourMechanic come to your location to diagnose and inspect your vehicle to ensure everything is in proper working order.

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My car is making a knocking noise – 2003 Toyota Corolla
ANSWER : Hi there. From the description you have provided, the knocking noise in your engine is serious. The engine oil light coming on while driving down the highway, then quit running is equally concerning. Assuming you have had the engine’s oil level and condition checked, this leads me to believe the engine has had an internal failure. The knocking noise could be caused by a spun connecting rod bearing. An engine overhaul or replacement would be required. I recommend having your vehicle’s engine knocking noise be inspected and diagnosed by a certified technician, such as one from YourMechanic.

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Car is making a metal scraping sound – 2001 Saturn L200
ANSWER : There are really only a couple possibilities: if the noise started "suddenly" or abruptly, as you describe it, you may have picked up something from the road that is somehow "lodged" somewhere rubbing a wheel, shaft (axle), or other rotating part. That possibility also could include something metal ON your car that has moved out of position (gotten loose) and is rubbing on a rotating component or suspension.

The second possibility is you have a part failure in the braking system (possibly worn out pads, but what you are describing is not consistent with that) or an internal part failure potentially in the transmission, torque converter, differential, axle (CV joint) or similar "moving" part.

For the first possibility, you might be able to track it down using a visual inspection but you have to get the car pretty far up off the ground. The second possibility would involve applying wireless "chassis ears" to various parts of your car and driving it to pinpoint the exact "area" (or component) which is generating the noise.

Once the area is pinpointed, it is fairly easy to go from there and identify the exact problem. Prior to using tools such as chassis ears, of course, it is possible that YourMechanic can pinpoint the noise just based on actually hearing the sound and its apparent location. Sometimes noises are so "diffused" throughout the vehicle that chassis ears make the diagnosis much more efficient though.

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Car is making a grinding/clanking sound
ANSWER : Hello. It sounds like you had a total transmission failure. When you have a severe internal breakage, like a sun shell or clutch pack, this will occur. The transmission will need to be disassembled and rebuilt in order to fix this. You will most likely need to take the vehicle to a transmission specialist that specializes in these transmissions. If you would like to have the car inspected first, a technician from YourMechanic can come to your car’s location to determine what is causing the grinding sound.

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Car makes a loud sound every time I start my car, at idle, and when driving at low speeds
ANSWER : Hello. The first thing to check would be your fluid levels. I’m not sure what type of noise you have, but ticking noises at idle can be linked to a low oil level. If there is a vacuum leak, the should may be more prominent at idle then fade as the engine speed increases. A vacuum leak would generally turn on the Check Engine Light as well. I recommend having a certified technician, like one from YourMechanic, inspect the hard start and advise you on any repairs.

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My car makes several loud clicking sounds that go on for about 15 seconds, is it ok to keep driving the car?
ANSWER : There are a number of things that may cause a ticking sound, however one of the most common is usually when the vehicle is low on engine oil. This can happen when the engine oil is low and the lack of proper lubrication causes the valve train components to make a ticking sound for a period of time usually upon starting the car until the engine has enough time to pump the oil to the rest of the motor. Usually, this does not cause immediate harm to the motor, unless it is dangerously low on oil. I would recommend having a professional from YourMechanic come to your location to take a look at your vehicle and change your oil.

Read Full Q/A … : Car makes knocking sound