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.

A: As a car sits, all the residual oil (in the...

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

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: Does this vehicle have an interference engine??

This engine is an interference motor that most likely bent valves when the timing belt broke. An issue like this calls for major engine repair. Whether you decide to fix the engine or get a new car, be sure to...

Q: sounds stopped up

It sounds like your catalyst is broken up and clogged the exhaust. You may also have a problem with the engine flooding from fuel which could be caused by a bad fuel pressure regulator.

Q: Car revs high and jerks when first starting to drive car, while driving.

Hi There, It sounds like you may have low transmission fluid or a faulty transmission control solenoid. As you know, automatic transmissions use pressurized hydraulic fluid to change gears. Every time a gear change is required, the car's computer activates...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
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...
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.