Q: Knocking/Rattling sound in the engine bay on startup.

asked by on

I was wondering if it could be a faulty belt tensioner, since the problem is intermittent. Note that the rattling/knocking sound goes away after the car warms up. So you'd only hear it whenever the car is starting up from a few hours of non-use/ an overnight's rest/ on a cold winter day.

What do you think? :)

My car has 130000 miles.
My car has an automatic transmission.

It would be difficult to tell what is causing the noise without first inspecting the vehicle using a mechanic’s stethoscope on various locations to determine exactly where the source of the sound is. However, it is possible that the noise could be coming from the engine itself or one of the engines belt driven accessories. I would recommend enlisting the assistance of a qualified professional to listen to different parts of your engine with a mechanic’s stethoscope to find the noise. Possible causes of this noise would be valvetrain parts within the engine, rod/main bearing out of place within the engine, pulley/tensioner fault, water pump, etc. Once the mechanic finds the noise in question, they should be able to provide you with a more accurate solution to your issue. If you would like, an expert from YourMechanic can provide the diagnosis of the rattling/knocking sound for you, at your home or office.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Knocking/Rattling sound in the engine bay on startup.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Leaking coolant, dripping off engine block near oil filter. 2006 Dodge Ram 1500

Hi - yes, almost certainly this is the water pump bearing seal leaking. I would replace the water pump immediately. Modern water pumps have a remarkable ability to hold water right up to the instant they fail completely - resulting...

Q: What does the Maintenance Minder indicator mean?

Your car is equipped with a pretty advanced system designed to help you remember when most of your maintenance services are due. These reminders are shown in the Maintenance Minder on the dash of your car. The Maintenance...

Q: Transmission won't shift from first gear

You will need to have the car checked for the reason the check engine light is coming on? The vehicle is going into failsafe mode and not shifting transmission. Once you get the codes from the computer you can then...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.