Loud rattling coming from underneath the vehicle

When my car is coasting or in park, I can hear a very loud rattling sound coming from underneath the vehicle. The sound is not always constant, as sometimes it happens every 15 to 45 seconds, and sometimes it is almost constant.
Experienced mechanics share their insights in answering this question :
This could be caused by a loose lower cover plate. Trucks have a metal plate that protects the underside of the engine from debris. This plate is often removed for repairs and sometimes not all the bolts will be present as they tend to come loose from the cars vibration. This can cause a rattling sound under the vehicle. A certified mechanic will be able to pinpoint the source of the noise, and check the bolts for tightness and make sure none of the bolt holes are damaged. So that new bolts can be installed if some are missing.

How to Identify and Fix Common car Problems ?

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If the rattling sound sounds like it is coming from underneath your vehicle, you likely are experiencing a problem with your exhaust system. Exhaust system problems include catalytic converter problems, muffler issues or corroded pipe, can sound like light rattling to rocks shaking beneath your car.
The Problem: Variable cam timing (VCT) has been identified as one of the main causes of the rattling engine sound in the 2019 Ford F-150. The VCT system adjusts the timing of the engine`s valves to optimize performance and fuel efficiency.
Recommended Services. The rattle at idle could be caused by a variety of issues, such as any loose parts or panels, fuel injector noise, or the engine top end. The deeper rattle could also be caused by a few items such as a drive shaft, wheel bearing, or the engine itself.
A Rattling Noise from the Engine When Accelerating

Noises coming from the engine when you are pushing on the gas could be caused by a loose or weak timing belt, chain tensioner, cracked flywheel, or a broken flexplate. These issues will only get worse over time, not better.

You usually hear this noise when accelerating the vehicle. Most people call this a pinging or rattling sound. This noise is caused by an air/fuel mixture in the engine cylinder being ignited prematurely by the heat of compression as the piston is moving up on the compression stroke.
The Ford death wobble defect may be caused by premature wear or loosening of various components such as the ball joints, control arms, track bar bashing, damper bracket, or shocks. Unfortunately, fixing the problem involves trial and error.
Powertrain issues, problems, and complaints are some of the most common concerns that owners of 2021 Ford F-150 trucks have been experienced. Some of the most frequently reported issues include problems with the transmission, engine trouble, and difficulty with the four-wheel drive system.
It sounds like a light knocking or growling sound. Gear rattle is an audible noise transmitted from the impacts between the transmission gear teeth. A vehicle engine`s torsional vibrations (momentary angular acceleration) pass through a transmission causing the separation and resulting impact of the gear teeth.
Loud idling is usually caused by issues with cylinder compression. When there are problems with cylinder compression, you get an uneven fuel-air ratio. As a result, combustion becomes unusual. Having higher pressure inside the cylinder will result in loud idling noise.
If your car`s transmission is poorly lubricated, metal components inside of it will grind against one another. This can lead to a rattling sound as gears wear down inside the transmission. Even worse, these gears may eventually make the transmission unusable.
When your engine is lubricated properly with fresh oil, it should run fairly quietly. As the oil ages and it loses its ability to lubricate the components, the parts will start to move harder against one another causing friction and grinding. These rattling, rumbling, and knocking noises will be hard to miss.
What does a bad catalytic converter sound like? Often, a clogged catalytic converter sounds like a rattling noise is coming from under your vehicle and engine when you`re starting, idling or driving. Excess heat or damage in the converter can break apart the honeycomb materials, resulting in the rattling noise.
When the spark plugs malfunction, they reduce the effectiveness of the engine`s cylinders, which then causes the cylinders to rattle. These unpleasant noises indicate that the cylinders are being overworked and will lead to further troubles down the line.
A ticking, tapping or clacking from the top of the engine is usually indicative of a potential issue with your engine`s tappets. At first it can seem insignificant in volume, but gradually over time the `rattling` will get louder and indicate an imminent major mechanical issue.
There is a rattling sound. A lax timing chain, or worse, a broken timing chain with loose parts within the engine, will produce a rattling sound when your car is idling. This rattling sound is typically most prominent while the engine heats up and disappears after some time.
A rattling noise in that area can be a number of things including bad struts, timing chain issue, or bent suspension components. You should have the front suspension sway bar bushings or link arms inspected for loose or worn components and repaired as needed.

Relevant Questions and Answers :

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Loud rattling coming from underneath the vehicle
ANSWER : This could be caused by a loose lower cover plate. Trucks have a metal plate that protects the underside of the engine from debris. This plate is often removed for repairs and sometimes not all the bolts will be present as they tend to come loose from the cars vibration. This can cause a rattling sound under the vehicle. A certified mechanic will be able to pinpoint the source of the noise, and check the bolts for tightness and make sure none of the bolt holes are damaged. So that new bolts can be installed if some are missing.

Upon starting my car it makes a loud hollow noise. There is also a rattling sound is coming from exhaust pipe.
ANSWER : Hi there. The engine may have a misfire causing the exhaust pipe to have a rattling noise as the engine is shaking. Check the fuel injectors and the spark plugs and see if they are working and if they need replaced. Make sure that the exhaust hangers are not missing to make the pipe vibrate on the vehicle. If you need further assistance with your engine making a noise, then seek out a professional, such as one from Your Mechanic, to help you.

The engine is making rattling very high noise when you start the engine and constant.
ANSWER : The fact that the oil pressure drops when slowing down or stopping would suggest that the oil pressure is lower at lower engine RPM’s. This means that the oil level volume is low. The oil capacity in an engine is designed to correlate with oil pressure at any given RPM. When it is full, there should always be constant oil pressure assuming there is no oil leaks. I would suggest having an expert from YourMechanic come to your home to diagnose your vehicle and make appropriate repairs to your vehicle.

My car is making a loud rattle sound when idling and in neutral
ANSWER : There are several causes for the engine to rattle while idling. With your car, the heat shield or an under engine shield is most likely. The other causes are the AC compressor clutch, idler pulley, or belt tensioner. The heat shields are used between the exhaust and the underside of the vehicle to keep the vehicle cool and the heat from the exhaust directed out of the tailpipe. When the heat shields become loose, they can make a flapping noise when the vehicle is moving. To verify this, a qualified technician, like one from YourMechanic, will be able to diagnose the rattle and replace your heat shield if necessary.

Loud rattling coming from bottom of car
ANSWER : Hi. This should be inspected soon as damage to the underside of the car can be costly. There are metal and rubber mounts that hold up the exhaust system which over time can become loose. This could also cause damage to the catalytic converter which is used to clean the exhaust coming out of the engine. Both of these systems are costly to replace and it is much cheaper to prevent them from being damaged in the first place. One of our certified technicians would be able to inspect the noise to determine the location of the noise.

Engine light has come on, fans are coming on when vehicle has only been started for a few minuites and remain on
ANSWER : With the previous work that was done recently, it is very likely the problem is that coolant leak. If its not the leak repair that has failed, it may be an additional leak.

Have you checked the level of the coolant to see if you need more already? If you do, you need to have that leak repair verified. If its holding, and you have lost coolant, you have another leak. If the coolant level is the same, you may have a thermostat issue.

The fans coming on is a huge sign that the engine is overheating. Does the dashboard read that the engine is hot? Keep in mind that thermostats in your vehicle are designed to read coolant temperature.

If the coolant is too low and the thermostat is reading air, your dashboard will not read correctly. Look to your owners manual for further information on your specific vehicle’s cooling system.

Rattling noise upon starting and then louder rattling at idle if load is placed on engine such as A/C
ANSWER : Hi there. Given your mileage and your maintenance of the idler pulley, your problem is likely worn/weak hydraulic lifters (or other valve train wear) or the timing gear set. Starting the engine briefly (less than 30 seconds) without the serpentine belt attached, will eliminate noises from all accessories if the problem is with one of them. I would recommend having the engine inspected in person by a professional so that the rattling noise can be diagnosed and properly corrected.

There is a rattling noise coming from the exhaust. Car begins to jerk with this and sometimes it turns off.
ANSWER : You may have a catalytic converter that has broken up inside. The business part of the catalyst is made of ceramic material, (yes just like the clay pots) which is coated with the various precious metals that facilitate the reaction that cleans up the exhaust. If the catalyst is badly overheated, or if you bottomed on a speed bump and it suffered an impact, the material inside can break into smaller pieces. The pieces will sound just like stones rattling around inside a metal can. In the right conditions, one of those stones can shift into a position that blocks the exhaust and you have a sudden loss of engine power. Power that returns as soon as the stone shifts again and unblocks the exhaust. If you can crawl up under the car and strike the exhaust with a soft mallet, you might be able to hear the pieces rolling around. The solution is to replace the catalytic converter. It may also be necessary to replace some other exhaust pieces as sometimes the stones make their way down the system and settle inside the muffler. If you contact Your Mechanic they can send a technician to your home or office to check out your rattling exhaust and let you know if this is your problem and what can be done about it.