Knocking under car.
I have a very loud knock that sounds like it's coming from the driver's side wheel well of my car. The odd part is, the knock only happens when the car is rolling and the engine is not braking, turning, or under load. So the knocking doesn't happen when I accelerate, it doesn't happen when I brake, and it doesn't happen when I turn. It doesn't just get quiet, it stops completely. I've checked the u-joint, and both wheel assemblies. I'm at a loss…
My car has 200000 miles.
My car has a manual transmission.
Experienced mechanics share their insights in answering this question :
This is may be anything from wheel bearings to ball joints and struts. The fact that it only happens when the car is rolling and not under a load suggests that it may also be something as simple as something being caught in the wheel or axle assembly. Without hearing the sound, further diagnoses would be difficult. I would recommend having an expert from YourMechanic come to your home to listen and test drive to diagnose and repair.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
What to do – Check all suspension components, steering column, and your exhaust system. If you drive over bumps or potholes and you hear knocking noises from under your car, there`s a strong chance it`s your suspension or shock absorbers. The suspension consists of many parts, so have a mechanic isolate the issue.
As the bearings wear out, the pistons will start to rattle against the crankshaft, creating a very similar knocking sound. To fix this problem, you may need new bearings or other work done on the pistons or crankshaft — parts located deep in the engine, meaning this can be a time-intensive repair.
Signs of Transmission Problems
These sounds can indicate transmission failure. However, keep in mind that transmissions are made up of hundreds of parts, so knocking or clicking noises may also just be a worn-out case, or bearing, requiring a minor transmission repair.
A knocking sound is usually due to a problem with the internal components of an engine. Driving while you hear a knocking noise is not recommended. The more engine damage you cause to these internal components, the more difficult and expensive the repair job will be.
Knocking can damage the surface of the piston, the cylinder walls or the crankshaft bearings, all of which are expensive to repair. Modern computer-controlled injection systems can correct your fuel mixture to prevent knocking, but at the cost of engine performance.
If you notice that your gears feel stiff or sticky, you could be low on transmission fluid. Low fluid will slow the cause the response time from gear shifting to become increasingly slow and difficult over time. You may even hear a light knocking sound if the problem becomes dire.
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.
Adding more oil will make the noise go away, but it won`t solve the underlying cause of the noisy engine – the oil leak.
The knock sensor could be missing entirely and it would not prevent your car from starting. You can drive with a bad knock sensor, but it could have adverse long term effects on your engine if there is a lot of pre-ignition, and the car will not pass most state inspections until it is fixed.
This is dangerous because it increases air pressure in the cylinder more than is normal. This can puncture the pistons in the engine and cause extensive damage in some situations. The knock sensor of a car is a small, cylindrical part that detects irregularities and malfunctions in the combustion of the engine.
Spark Plugs That Are Worn or Misfiring
If your spark plugs are overdue for replacement, your engine knock could be attributed to that and you may also lose engine power.
Knocking can cause overheating of the spark-plug points, erosion of the combustion chamber surface, and rough, inefficient operation.
The noise could be a from a tire that is separated or one of the front axles joints being bad. If you do not feel anything in the steering when the noise is happening, then the noise is most likely from an inner axle joint on one of the axles.
Your car`s intake and exhaust valves can get stuck or wear out. This can lead to premature ignition inside the combustion chambers. It can also cause a rattling noise similar to the sound created by glass bottles clinking together when you accelerate.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
I put the wrong key in my car and a few weeks later my car just shut down and it will not start I believe it’s the computer but…
ANSWER : Hi there. What had happened is the wrong key set the security to the vehicle. This is to prevent the vehicle from starting with the wrong keys. Try removing the battery cables (+) and (-) for 13 minutes. During that time, put the original key in the ignition and turn it on. Activate everything in the car even though there is no power. Then remove the key and hook up the battery cables. The computer should have reset and reset the security. If the security is still being tripped, then I recommend seeking out a professional, such as one from Your Mechanic, to help you
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Replaced alternator on car 2 times each time shows it’s charging 14v let car run for a little bit then test drive and car voltage
ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.
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Today my car made a loud knocking noise and when I press on the gas pedal, the car doesn’t accelerate right away but when it does it makes a knocking noise.
ANSWER : The noise that you are hearing could be one of the rod bearings are knocking in the engine or the flex plate could have a loose bolt making the torque converter bounce around. I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose your knocking noise.
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Battery and oil light come on when trying to start car, take keys out try again car starts no problem and lights go away
ANSWER : Of course, don’t switch gears without being fully stopped, unless your Owner’s Manual or the manufacturer has alternative advice. However, the gear shift issue has no relation to the no-start problem you are describing. Inasmuch as you only have 6,000 miles on the car, the "constant on and off" that you believe has occurred is meaningless in comparison to the expected total vehicle service life. That is, assume what you perceive as "constant on and off", during merely 6,000 miles, might be equivalent to using the car "normally" for three years. A new car should be trouble free for at least 5 years, unless there is a defect, so your "constant on and off" is not a causal factor for any fault on the vehicle. What you might have is a defect in the ignition switch, or perhaps the immobilizer system, but if the problem is not in the switch itself, clearly there is an electrical problem.
If your vehicle is under warranty, by law the dealer MUST repair the issue you are describing within a prescribed time frame and number of "attempts", otherwise the dealer will run afoul of Federal and state Lemon Laws that give you very specific rights, and recourse (contact an Attorney; we are Mechanics, NOT attorneys). Consequently, if the vehicle is still under warranty, to save yourself money do be sure to seek a resolution from the dealer. If the vehicle is not under warranty, obviously a certified Mechanic from YourMechanic could identify the electrical fault and resolve this for you. If you want to go that route, please simply request a no start diagnostic -electrical system and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
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My car will not start Intermittently. I purchased a new battery 2 weeks ago and yesterday the car wouldn’t start. Got a jump and
ANSWER : The issue you are having is probably due to an intermittent fault in the starter motor itself or a deficiency in the starter electrical circuit, for example a large voltage drop due to a poor ground or a high resistance connection. These issues can be readily diagnosed and resolved on a mobile basis if you request a hard starting diagnostic. If you request that diagnostic, the responding certified mechanic will get this resolved for you promptly. Based on Toyota’s Factory Service Manual, the battery should not be disconnected if the vehicle engine is running. The battery acts as a large resistive voltage sink and consequently taking the battery out of the circuit, while the alternator is still running, can create a voltage spike on the car’s electrical system which is not good for voltage sensitive components such as the engine computer. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
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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.
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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Power steering loss, no belts are turning but the car is running fine. I also have a soft pedal. Whats wrong with my car?
ANSWER : I have only seen this situation once in my 30+ years and it turned out to be a broken crankshaft pulley. Belts are driven by the engine. The crankshaft pulley spins the belts, which in turn spin the air conditioner compressor, power steering and water pumps, and the alternator. The vehicle should be towed to your local repair shop and not driven. Without the water pump spinning to circulate the coolant, the engine will quickly overheat and result in more extensive damage.
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Should I buy this car for $1700
ANSWER : Prior to buying any car, drive the car around and listen for any noises. Then do an inspection on the vehicle to make sure that it is safe to drive. All cars will need maintenance, but if the car was kept up, then the maintenance should be to a minimum.
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