Engine compartment noise.

©hester

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#1
Make
Nissan
Model
Altima
Year
2004
Miles
175000
Engine
3.5
This noise occurs right after the vehicle is turned off. Noise can be duplicated by cycling key on key off. It has a rhythm similar to that of a windshield washer pump and the tone of a step motor/valve. It seems to emanate from the middle/bottom of engine and cycles 3 to 4 times b4 it stops. It's like something is trying to reset or recycle itself. No drivability issues. No check engine light.

Has anyone come across anything like this?
 
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©hester

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#2
100 people and not even a hint? I was able to get under the car today. It sounds like the noise is internal to the engine. Hard to pin point with or without a stethoscope. Any clue what could cycling inside the engine? It's very reminiscent of a cycling step motor/

Any WAGs out there?
 

billr

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#3
Well, I didn't answer before because a WAG is all I had to offer; was hoping you could get something better. So...

It looks like that has an electric "drive-by-wire" throttle, and I suspect it is a (hefty) stepper that operates it that you are hearing. Yeah, you seem to be hearing it someplace else, by noises are notoriously hard to locate or identify accurately.

The only other things I can think of with little motors that come on briefly at key-on are HVAC blend doors, trans actuators, active suspension, seat belts, and fuel pumps; maybe ABS too?. Those sources are just as far from the "engine insides" as the TB. Does this engine have "variable" intake runners? Maybe those are electric actuated. VVT might be another possibility, but I have only heard of VVT that is actuated by oil pressure, never a motor.

See? Lots of guessing!
 

©hester

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#4
Hey Bill. Thanks for the response. It is a drive by system. The throttle body is a convenient location to get an ear on for a listen. However, with an ear right next to it, the noise seems to emit from somewhere other to where I'm listening. I will remove the snorkel to verify any moment of the throttle plates.

Although this noise will occur with the key is turned on, it was first noticed and is predominant after the key is turned off. I thought of a trans solenoid/actuator noise, but after being under the car, it seems louder under the oil pan. Electric oil pump? I don't one of the those exits.

Not sure on variable intake runners. I don't have any experience with Altimas. Was that a thing in 2004? I will look at the ABS. WT?

Again thanks. I'll let you know what I find.
 

©hester

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#7
Thanks Dan. Point taken. Never too old to learn something. I saw that when I was rooting around, but dismissed it when I saw the vacuum hose.
 

©hester

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#8
Problem solved. It was a defective motor mount. This is some sort of an self adjusting motor mount. I understand that there is some sort of motor inside the mount. The sound was the motor trying to make adjustments.. Result, new mount, no noise.

Thx for all the replies.
 
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#9
Unbeiliveable. I can't keep up with the new innovations. Thanks for letting us know. What's next, motor driven cigar lighters or hood ornaments?
 

nickb2

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#10
Yeah, it's called active suspension. @Jack, here is a link.

These would have been nice on fleetwoods/caddy's with the airplane package elvis liked so much.

For A quebec canadian guy, I sure know about usa culture.

 

nickb2

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#11
I remember older caddie's that would cut spark. That WAS high tech back then. Look now at what a car can do.

Who would want a caddy cutting cylinders whilst cruising. California law at it best and all the lobbying ppl renting right next door back then.

Not much has changed actually in 2018. Worst car I ever drove. A 350Z super package. It (the ECU) cut injection when wheel spin detected. WTF do I need a rear wheel drive car for if this thing limits my every movements?:eek: Trac control, VSC, ABS with active air suspension and now active motor mounts. Which BTW are not knew/new. Can never remember if english needs a "K" in front of new.

The young guy's at the shop saliva big time when they see a car with a dizzy. We just don't see them any more in the shop in the sort of climate I live in. Much more available in climate such as calif and similar road salt free regions.