This past weekend I put a new Valve Cover Gasket on my car and cleaned out the
inside of the cover to get rid of all the built up crud. When I got everything back
together and started up the car just to make sure it was tight enough and no leaks
(yes I refilled the oil to right level) I heard a decently loud almost whistle coming from the engine bay.

I have heard this noise before but really never though much of it. It sounds like the hum of a small electric motor spinning. As I was driving around this weekend I did notice that it is speed dependant (I go faster it gets louder) and almost sounds like my a turbo winding up. It does come and go but I cant narrow down what causes it. If i play with my heat/AC controls (both temp and fan speed) i can get it to stop sometimes but not always. It makes noise with or without the heat/AC on.

However it does not always make this noise. It would go away then come back and there was no specific time period that it would either be heard or not heard. Although it was incredibly windy in my area this weekend I doubt that caused it as i first heard this noise with the car in my closed garage (resedential not a mechanics garage)

Any ideas? Could it just be the alternator since that would be connected to my speed? (alt spins faster as i go faster????) My capacitor shows that my alt is working good (14.3-14.5V when driving with stereo off) and 12V when engine is off.

 

Sounds like alternator whine. If it is, then it would be rpm dependant, and the sound would be coming from the speakers. The more electrical accessories you turn on, the louder it'll get. Try this...: Drive with the headlights, A/C, and rear defroster on. (I'm assuming you have a system since you have a capacitor. Have the stereo on, but the volume all the way down.) With all these things on, the whine should be more pronounced.

Cause: something not grounded well enough; poor quality RCA cables picking up interference; RCA cables run too closely to amp power cable and/or ECU

Fix: Make sure all grounds are attached to bare metal. Clean all underhood grounds. Make sure RCA cable is not running close to the ecu or amp power cable.

EDIT: Although called alternator whine, it is not actually a problem with the alternator. Alternator whine is very common with aftermarket audio systems. I solved every alternator whine I have come across by doing the 3 things I suggested. Keep in mind, just 1 bad ground can cause it, whether it is directly related to your system or under the hood.

Oh, something else I just thought of... Some aftermarket decks require that the unit be ground to metal, and not to the factory wire harness. This is because the factory ground is inadequate for many high-power decks.

 

hey whats this about the RCA running to close to the power wire?? Mine run side by side, should i change this? what will happen if i don't? Can i be getting better sound if i move them apart? <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">Sounds like alternator whine. If it is, then it would be rpm dependant, and the sound would be coming from the speakers. The more electrical accessories you turn on, the louder it'll get. Try this...: Drive with the headlights, A/C, and rear defroster on. (I'm assuming you have a system since you have a capacitor. Have the stereo on, but the volume all the way down.) With all these things on, the whine should be more pronounced.

Cause: something not grounded well enough; poor quality RCA cables picking up interference; RCA cables run too closely to amp power cable and/or ECU

Fix: Make sure all grounds are attached to bare metal. Clean all underhood grounds. Make sure RCA cable is not running close to the ecu or amp power cable.

EDIT: Although called alternator whine, it is not actually a problem with the alternator. Alternator whine is very common with aftermarket audio systems. I solved every alternator whine I have come across by doing the 3 things I suggested. Keep in mind, just 1 bad ground can cause it, whether it is directly related to your system or under the hood.

Oh, something else I just thought of... Some aftermarket decks require that the unit be ground to metal, and not to the factory wire harness. This is because the factory ground is inadequate for many high-power decks.</TD></TR></TABLE>

hey whats this about the RCA running to close to the power wire?? Mine run side by side, should i change this? what will happen if i don't? Can i be getting better sound if i move them apart?

 

Some people say they get a cleaner signal by running the power wire and RCAs on separate paths. If you're not running well-shielded RCAs, this would be more important. If you don't have alternator whine (usually caused by bad grounds and not RCAs), and if your signal sounds pretty clear to you, don't worry about it.

In my friend's F-250, I had no choice but to run the power wire and RCAs side-by-side, b/c all my other options were already full with power wires running to other equipment. (He uses his truck for work.) We used some higher-quality (read: expensive as f#%*) shielded RCAs and didn't have any problems with it. Since then, I have re-wired all the power cables utilizing a distribution/fuse block. I was then able to re-run the RCAs on a separate path. We noticed no difference, but I was re-wiring it for different reasons anyway.

 

This makes a lot of sense to me and when the temp goes above 30 and 40MPH winds ill go check it out. I think your right on that it is a ground problem but its gonna be a tough time finding it. My stereo has been in my car for over 4 years now with the current head unit 2-3 years old. I ran the power on the passenger side of the car (battery side) and the audio cables under the driver side with the Amp mounted under the driver's seat. The capacitor is mounted on the floor on that little hump in the middle of the back. (2 door never have more than 3 people in my car for comfort reasons) So the interferance there I highly doubt. It very well could be that I did not connect a ground well enough or lost one to my head unit though. I noticed that my head unit is not working well after doing the valve cover gasket (disconnected battery) There is a bass mixer feature that is supposed to be lite up and it currently will not, and it sounds as though my set up isnt sounding right.

Could this simply be a battery connection problem? A problem with the ground on the valve cover? the feed to the distributor? Those are the only things electrically I "played with" before hearing this noise.

Also I dont think I emphasized this enough in the first post. The sound is audible with the speaker sound all the way down, and from OUTSIDE the car. It is very noticble with the hood up. And yes it is RPM dependant not speed. I mis-spoke as I was rushing to get the post in, leave work and catch my train home. (damn cities take all the fun out of commuting)

 

vaccum leak

 

If you've got an audible whine from under the hood (and it wasn't there b4), most likely your battery ran down while you were working and the noise you're hearing now is the alternator laboring to recharge the battery. If everythings working properly, it should stop once the battery reaches full charge capacity.

In answer to your cable routing question; yes, you can pick up an audible electrical whine thru your audio cables if they are routed incorrectly or are unxhielded. It's a condition called inductive transferance; a phenominon where the electrical energy (and noisy) from one wire can be induced (note the similarity to the word induction) in a wire running parallel to it.
An example would be the digital communications. wiring called Twisted Pairs was developed just for this reason.

P

 

So basically in the 15-20 minutes i had my battery disconnected and everything turned off in my car it drained the battery? the battery is maybe a year and a half old IF THAT. and its not a cheap knock off from walmart nor is it a expensive fancy one. I just didnt think the battery could lose charge that fast. Is there a way to test to see if it is the battery or not? Or should I just clean up my grounds and see if I can fix it that way and wait? The car does sit for prolonged periods of time without being driven (2-3 weeks of inactivity is not unusual).

As for vacuum leak, is that really applicable here? Does anyone else feel this to be valid? I did have to disconnect the one vacuum line from the valve cover, ill try to check that out sometime soon as well.

So far here is the checklist I got from you all
1) check and clean grounds
2) make sure system wires are not in near proximity to each other to prevent arching (N/A good sheilded wires + they are almost 4 feet apart buried beneath the cars upholstery)
3) vacuum leak (all i can think of is that one since vacuum line to the valve cover)
4) battery lost charge (I drove 2 hours straight mostly highway never under 50 MPH except for stop lights and the nose stayed with me most of the drive, I do have 215k approx on the car, could my alt just be slowing going the way of the buffalo?)

 

The important point to make is that it is not uncommon for an alternator to whistle while it's charging. It's a matter of degree really.
No, Battery will be ok. disconnected an hour and a half won't do anything.

 

OK, thanks for the input everyone. I'll look at those things I listed hopefully tonight, weather permitting, and get back to you all with what I find

 

back to the power wire and rca running side by side.

i did that one time, and didnt think anything of it, until i heard just a small whine, but when i turned the volume to like 3 or 4 on my HU, there was a HUGE screeching, nails on chalkboard, shoot your mother, type sound.

so just from experience...even if it isnt your main problem here...i would fix that

 

It's def not my problem here, as I've stated 2-3 times now. I ran my power on passenger side and RCA on driver side of the car. The only place they come remotely close together is at the actual amp. I might not know car mechanics too well yet, but I do have common sense and throughing a pure voltage line next to a fine wire that is carrying specific frequencies and voltage changes to the milisecond is just plain wrong. I had a friend once who thought it a good idea to put cheap walmart wires in his electric guitar. you think nails on a chaulk board is bad.......