tbennett017

I have been trying to diagnose a sound in my car. It is a hum, or solid tone that does not change with RPM or road speed. (It gets drowned out at higher speeds, but is still there afaik) It does not vary in frequency at all. The best place to hear it is INSIDE the car above the back seats, and every attempt to hear it outside the car has led to nothing. I have one of those probe stethoscopes, (touch it to parts to hear them) and I can't get that sound no matter what.. Its not the fuel pump, not the speakers inside the car, not any rotating parts I can reach from under the deck-lid...

Someone mentioned an electric air pump. Does the 964 have one of these? The sound mainly happens after driving the car for 10 mins or more.. but now it is happening sooner and sooner

Average temps here are between 50 and 70 deg F, FWIW....

Also, where should I go for a better look at the engine? I wanted to buy the 911 engine rebuild book from Pelican, but it doesn't cover the 3.6. Is it still a good book to have? Outside of this, I have Adrian's book..and the PET...but what else would give a good look at the engine?

TIA!

DaveK

Rear blower?

dutchcrunch

rear wheel bearings?????

parsecnc4

Fuel pump? It could also be brake booster if it is a C4, at least that is what I recall reading somewhere.

Indycam

Rear blower? X 2

Unplug the wires to the blower and go for a drive .

"rear wheel bearings?????"
"does not change with RPM or road speed."
"mainly happens after driving the car for 10 mins or more.. but now it is happening sooner and sooner"

"It does not vary in frequency at all."
That sounds like a electric motor thats running at one speed .
The rear blower has those bearings that go bad .

mojorizing

It's probably not it, but let me tell you this story. I had a slight rattle coming from the rear of the cab interior. I thought it was a loose third brake light. Took that apart and found that the cover wasn't tight, fixed it.

The sound was still there!

Took apart both speakers, found plastic cover/screen mesh loose, fixed it.

The sound was still there!!

Now I'm a man consumed by this slight rattle. I needed to find the source or go to therapy.

That day I took my wife to dinner in the car, and she asks what's bothering me. I said "Hear that rattle? It's driving me crazy!" She said "That's not a rattle, that's a tapping". After about 15 minutes of in depth analysis of semantics and the difference between the definition of a "rattle" and "tapping" she promptly reaches back and touches the button that latches the back seat back rests. Sound vanished. And the button hasn't made a sound since.

Moral of the story, have your wife listen to it.......

Indycam

"Moral of the story, have your wife listen to it"
No No No
Moral of the story ,
have mojorizing's wife listen to it ,
she has the talent that big companies pay big bucks for .

tbennett017

when can your wife come up to PDX?
This sound is making me nuts.
It isn't any of the above, but thanks for the thinking. yes... it really sounds like an electric motor running... precisely at a frequency that makes my brain leak out of my ears in a bloody flux.

I checked all the sources mentioned... The air blower could have been it.. but the bearings/assembly is completely quiet... And doesn't that run after the car is off if it is really hot? That sound I know about... The brake pump is much louder...

The only thought I have is that the fuel pump might be transferring the sound somehow... but that's the only electric motor that I can account for that might make sounds in that scenario...

Insanity is nigh!

Indycam

Did you unplug it and go for a drive ?

Oil cooler fan ?

parsecnc4

If it is fuel pump like I had suggested before, I believe you can confrim that by not starting the car but leaving in the "ON" position.

MisterRisky

I'm glad that I'm not the only one having these types of conversations with my spouse.

dutchcrunch

its hard to tell exactly how it sounds,

could it be the rear speakers getting some feedback. before you say it , i heard of people getting noise from their speakers even if the radio was off.

dutchcrunch

could your engine fan bearing be going out, or the fan belt indicator unit , ithinks that what it called, the unit that tells if the fan belt is broken, the little black plastic wheel by the distibutor.

MisterRisky

I don't mean to discourage brain storming, but the fan bearing should change sound with engine RPM and you would defiantly be able to hear it from the engine compartment with the lid up. At least I could hear mine when it began dying a few months back.

dutchcrunch

JD, thats correct. hard to troubleshoot it with out hearing it. think maybe his heater hose off the heat exchangers is loose or cracked allowing air to escape and making that noise. sounds good does it not???