Skip the auto shop - Our mechanics make house calls

Q: My car is making a loud rattling sound, but only when it's cold and I've just turned the engine over.

asked by on

When my Mitsubishi Outlander has been sitting for awhile and I turn the engine over on the right side of my car it makes a loud knocking sound but only for a moment the sound goes duller as my car warms up. My car has 146068 miles.
My car has an automatic transmission.

As a car sits, all the residual oil (in the hydraulic valve lifters, for example) drains down to the oil pan. When you re-start the car, particularly when the weather is cold and the oil is most viscous, the valve lifters and all the other rotating engine components have to be re-supplied with oil under pressure. The problem is that, until the oil system reaches full pressure, there is the potential for noise, including what might sound like rattling noise from the valve train.

If you suspect the noise could be coming from belt driven accessories, such as the alternator, water pump, power steering pump, and so forth, you can disconnect the serpentine belt from the engine and run the engine just briefly (as before, that is after it has sat idle and is cold) and see if the noise disappears. But, more likely than not, the noise is simply due to that brief interval when your engine lubrication system is not fully pressurized.

There are aftermarket engine pre-lube systems that you can add to your car to avoid hearing even this momentary noise. This pre-lube system is operated via a solenoid that is wired into your ignition switch circuit so that the instant you turn the key to the "on" position (before "start"), a valve opens from a small pressurized cylinder containing oil, instantly creating oil pressure throughout the engine even before you start your car.

I recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why the car is making a noise and suggest any needed repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  • Home
  • Questions
  • My car is making a loud rattling sound, but only when it's cold and I've just turned the engine over.

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: Car dies after charging battery

The symptoms described for your Mitsubishi Outlander lead me to believe you are dealing with a weak battery. As batteries age, they lose the ability to hold a charge. The Check Engine Light could be on as a result of...

Q: Rattling from timing chain tensioner

Hello. Ford motors commonly have a problem with the timing chain making noise over time. Most of the time, the problem is that the timing chain guides are worn out. This could be causing the timing chain to hit metal...

Q: How long does it take to remove and replace a throttle?

Hi there If the throttle sensor is not working, it's most likely caused by an electrical issue; as opposed to a mechanical problem with the throttle body or other components. The best thing to do is have a professional mobile...

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.