Good Noise?

[wallstreet]

When I turn the ignition key to ACC, I hear a humming sound for about 10-15 seconds. Its perfectly normal. I think all 4runners have this. Seems like the the oil pump is working to circulate oil before I crank the truck. Not sure but was wondering if this is true. Does anyone know what processes take place in the engine when the ignition is set to ACC.

Maybe it might be a good idea to turn the key to ACC for 10-15 seconds before cranking to help the engine at cold starts, esp in winters.

 

[drmorbius]

When I turn the ignition key to ACC, I hear a humming sound for about 10-15 seconds. Its perfectly normal. I think all 4runners have this. Seems like the the oil pump is working to circulate oil before I crank the truck. Not sure but was wondering if this is true. Does anyone know what processes take place in the engine when the ignition is set to ACC.

Maybe it might be a good idea to turn the key to ACC for 10-15 seconds before cranking to help the engine at cold starts, esp in winters.

You are probably hearing the power brake booster which uses an electric motor to drive a pump and fill a reservoir. Most cars use a vacuum operated booster that uses engine vacuum and requires that the engine be running.

 

[03 Limited]

You are probably hearing the power brake booster which uses an electric motor to drive a pump and fill a reservoir. Most cars use a vacuum operated booster that uses engine vacuum and requires that the engine be running.

Or maybe he is hearing the fuel pump priming?

 

[drmorbius]

Or maybe he is hearing the fuel pump priming?

Well that's all the way back in the fuel tank and I can't hear mine but I can hear the booster.

 

[wombie]

Brake booster gets my vote, if only because it's right up by the drivers side of the hood.
They can shake about quite a bit too (mine had to be replaced because it was sending vibration up the brake pedal every time I braked...talk about annoying).