Hum in interior.

[bobwhite]

We have developed a hum that starts when the motor is running in our 90 Reatta. I checked under the hood and it is not coming from there. I checked to make sure the brake pump only came on if the brake pedal was pushed a few times. I listened in the trunk and under the car, no noise, only in the interior can it be heard. I took it to a Buick dealer and they had it for two days. They said it hummed all the time they had it, but where unable to locate the source. They suggested we change the fuel pump and gas tank because there is a old dent in the tank, but if that wasn't it, too bad. The radio is turned off as is all the other accessories. Any ideas? <p>[This message has been edited by bobwhite (edited 01-31-2001).]

Might check the dc-ac inverter for the console if its an 88 or 89. I found on my 89 when I was trying to fix the PRNDL shift<BR>electoluminescent ligthing that I could get the invert to hum. Pull the ash tray out and see if you hear it. Of course this would only occur with the lights on.

[bobwhite]

When I switch the key on I can hear both the brake and the fuel pump run for a time. Then they stop and you have the hum. The motorized antenna works fine. (3rd one).

Sounds like the fuel pump to me. Do you hear it if you turn the ignition switch to accessory?<P>Also, does the antenna go up and down like it should? If the cable is broken the motor will run continuously.

[Greg Ross]

A relay perhaps that's not fully cycled? Best I can suggest is systematically pulling fuses and relays one at a time until the the hum stops, that will at least narrow it down to the particular circuit.<BR>Remember there is a relay center under the hood as well, left front behind the washer resivoir, at least on the '88.<BR>Hope this is of some help,<BR>Regards,

[Reatta Man]

Hmmm.... <P>You hear the noise with the key on and the engine not running after the brake pump and fuel pump shut off? Wow...this IS a good one. This would probably stump Click and Clack. <P>You didn't say if it sounded like a high-pitched noise or a low-pitched tone. Usually a hum suggests a low noise, so I will assume that it is a low tone. It sounds like the old tube-type radios from the 40s and 50s. They had a component called a vibrator which actually did hum louder as it failed. That makes me think it is either one of the 'black boxes' under the console, or the radio. <P>For that reason, I suggest pulling fuses one at a time until it goes away. That should at least isolate the circuit and give you a place to start trouble shooting. Remember there are two fuse blocks--one on each side of the console under a carpet-covered door.<P>If that doesn't stop the hum, then I'd suggest putting your hand on each panel of the interior, and see if you can feel the hum. Perhaps it is a vibrating or loose component using a plastic panel like a speaker's cone amplifies the sound from the speaker's coil. <P>Here's another suggestion: the A/C fan. If you've recently gotten leaves or other debris near the air intake at the base of the windshield, a small piece may have gotten in near the squirrel cage fan. On a lot of GM cars, the fan runs anytime the key is on, even if the climate control system is turned off. If it's in there rubbing against the fan, it would possibly sound just like a hum. If you are not sure, disconnect the fan motor under the hood. <P>The only other thing I can think of that might not be cycling off completely that is inside the car is the theft deterrent module that is in the left rear side panel behind the driver's seat. <P>Good luck!<P>Joe<p>[This message has been edited by Reatta Man (edited 02-01-2001).]

Hi, Bob.<P>I am new here, and still need to reg, but I too have noticed a "Humm". It isn't the fuel pump sound that you here while starting. And it shouldn't be the brake pump because it occurs for me while jetting down the freeway....though I'm not familiar with this ABS system yet.. so I'm not sure. Someones replay said something about the shift lights and the Inverter. I'm going to check that one today, because I've noticed an occasional flicker in those lights...*crossing fingers* <BR>...one question, I am in the process of getting a serv manual, but until then, I want to get rid of the occasional Loping of the RPM's. *Does anyone know the actual #'d octane fuel I SHOULD use? I plan on changing the timing chain, plugs, wires, and coilpackthing, before too long. I just don't want to be running it incorrectly while I'm waiting for a manual.<BR>ThanX<BR>Jon-88

[bobwhite]

The hum is there only when the engine is running. It is about a 100 HZ hum. Everything seems to work OK.<p>[This message has been edited by bobwhite (edited 02-01-2001).]

Sounds like you better scrap put the car!<P>(I will take the vent windows off your hands...)

How about an exhaust leak or an exhaust component rubbing on the chassis?

[wally888]

I had a simular hum w/ engine running but it changed frequency as the transmission shifted.<BR> Broken doughnut hanger on the exhaust, just behind cat. Replaced. Noticed the other one has broken but I don't hear the hum as pipe isn't hitting frame as it was before. I would check there.<P>------------------<BR> <A HREF="http://www.reatta.net" TARGET=_blank>www.reatta.net</A> has supplemental info re.88, 89 and 90 Reatta Brakes.<BR>Please inform me of any new info, info needing editing or errors. A work in progress.

I'm not sure about Bob's "humm", but if his is the same as mine, I don't think we have anything rubbing or vibrating. It is a definate low pitched "humm" which sounds like a motor or pump either normal or failing or even possibly an electrical Humm. I hear mine from the interior while the car is running and usually at highway speeds when every thing else is quiet. At first, I thought it was coming from behind me (behind drivers seat, back of car) but after reading previous posts I listened closer to the dash and believe it might be from further up or below. Does this sound like your "humm" sound Bob? I will be taking a longer look at it this weekend. Hopefully I can pinpoint it. If I do I'll let you know here. This sound is intermittent, it seems to start and stop with nothing precluding it. I'm making it a MISSION this weekend, cross your fingers.<BR>And no I'm not scapping mine because of a humm, and I dought Bob is either. LOL <BR>My car is now permanently guarded by my Doverment, "Splinter". His house is located in the garage, with the car, and directly under the vent window. And I think he likes the car better then he likes me.

[bobwhite]

You have described my problem exactly. One thing I will check is to see if it is coming from the speakers. Some car amps are on even when the radio itself is turned off. A bad amp or poor ground to it can cause this. I'll look in the service manual and see if it covers the stereo.<BR>I checked and the hum is not coming from the speakers<p>[This message has been edited by bobwhite (edited 02-03-2001).]

bobwhite The possible reason your reatta is humming would be, because it does`t know the words!<P>PS might look for loose heat shield or broken spot weld on some kind of protective shield in the exhaust sys.In the BOOK it mentions insulators to restrict vibration & noise into the car<P>------------------<BR>

Find that little vibrating thing and remove the battery.

[bigrog]

A little help here. You stated earlier that the hum was only present when engine running, then later stated it was there without engine running? which is it? Most importantly, does it make your back feel good while driving? If so, let's figure out how to duplicate it, sounds like a nice upgrade!!

[bobwhite]

Sorry about the grammar and dangling modifiers. It only appears with the motor running. No, it doesn't rub my back, or other nice things, and since it is a low frequency, it is hard to localize. If it is harmless, I wouldn't mind it. I just don't want someone to tell me, "If you would have only brought it in sooner".

[wally888]

Does it hum w/ key on, engine off?<P>------------------<BR> <A HREF="http://www.reatta.net" TARGET=_blank>www.reatta.net</A> has supplemental info re.88, 89 and 90 Reatta Brakes.<BR>Please inform me of any new info, info needing editing or errors. A work in progress.

[bobwhite]

The motor has to be running. Speed has no effect on the hum, will do it when parked. Will not start doing it for various times, but when it starts, it doesn't stop until you switch the motor off. It's not a rattle like a loose shield. I listened in the trunk, and under the hood, and under the car, but the hum is only in the interior. Everything seems to work, and no warning lights.

[wally888]

Guess if I had the problem, I would either borrow a Dr's. stehascope?( you spell it!) or stick a piece of vacum hose in my ear and search!<P>------------------<BR> <A HREF="http://www.reatta.net" TARGET=_blank>www.reatta.net</A> has supplemental info re.88, 89 and 90 Reatta Brakes.<BR>Please inform me of any new info, info needing editing or errors. A work in progress.

[Reatta Man]

Wally, <P>They make a mechanic's stethoscope now; bought one years ago. Great for figuring out if it is the alternator, power steering pump, water pump or belt tensioner making a noise on just about ANY late model GM car. <P>Bob, as for your hum, did you try the things I suggested in an earlier post?<P>Joe

[bobwhite]

I will try the rubber hose to locate the hum. I have been under the weather for a few weeks, but plan on trying all the suggestions as soon as possible.