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2001 Montana weird humming/vibrating noise

KrystaF

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Hello all, I'm new here and have a question. I have a 2001 montana and it's been a good van for about two years for us. However, we have wondered about this noise we keep hearing. When it's in idle or right after we turn off the ingnition, we hear a humming/vibrating noise coming from what seems to be the rear of the van. It sounds like it's coming from under the third row of seats. If the ignition is off, if I open the driver's door, the noise stops. Otherwise, it goes for about 30 seconds. If the van is in idle, it will go for 30 seconds, then about every two minutes or so, it does it again. It's rather loud and everyone who has ridden in our van asks us about it and I can't figure out what it is. Even my stepfather (who is my mechanic) has worked on cars and vans for over forty years and he doesn't have the slightest idea what it is. We bought our montana used so it doesn't have a warranty or anything and taking it to a dealer is not an option.

Has anyone else encountered this strange noise? Does anyone have any idea what it could be? Should I be worried?

Aside from an electrical issue with the cruise control, the car runs great. We have to keep replacing tires but that seems to be a common issue with minivans. I'd appreciate any advice here. This mystery noise is driving me nuts! Thanks!
 

Roadrunner

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San Jose CA
sounds like your fuel pump..how do you turn the car on? do you put the key in and turn it all the way untill the car is running..if so, you should put the key in and turn it to the on position without turning the car on and listen to what you hear.. if you hear what you always hear then it's your full pump..you should try replacing the fuel filter and gas cap..it might fix the problem..if not then you might want to look into the pump going bad
 

KrystaF

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I can ask my stepdad about both of those things I guess. I really don't know much about cars myself but I do know that our shocks are totally shot in our van. We've been meaning to get them replaced but that's not been the priority for a while with four kids to shuttle around so as long as it's driveable, we've let it be. We did have to have the entire undercarriage inspected and several mounts (I think?) re-welded last summer. The guy at the garage said had we waited any longer, the axles would have shaken apart. I know when we had that done, we were told our shocks were bad. I feel every crack in the pavement while driving. Not sure if that has anything to do with the sound.

Also, is that noise the only symptom of a bad fuel pump? If not, what else should I look for? Thanks so much for the advice.
 

old man

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The parts places list a leveling pump for 2001 Montana. The fuel pump wouldnt run with the switch off. Im with Steel City on this one.
 

Roadrunner

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The parts places list a leveling pump for 2001 Montana. The fuel pump wouldnt run with the switch off. Im with Steel City on this one.
You can put a level suspension on it but it does not come with it..on alot of website they show air suspension kits for my ride but none of the models came with one..
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Roadrunner

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I can ask my stepdad about both of those things I guess. I really don't know much about cars myself but I do know that our shocks are totally shot in our van. We've been meaning to get them replaced but that's not been the priority for a while with four kids to shuttle around so as long as it's driveable, we've let it be. We did have to have the entire undercarriage inspected and several mounts (I think?) re-welded last summer. The guy at the garage said had we waited any longer, the axles would have shaken apart. I know when we had that done, we were told our shocks were bad. I feel every crack in the pavement while driving. Not sure if that has anything to do with the sound.

Also, is that noise the only symptom of a bad fuel pump? If not, what else should I look for? Thanks so much for the advice.
the nosie your hearing is only caused by say, something running like a fuel pump or a compressor like suggested up above...but most likely someting that has to do with electrical systems..since I am a gm tech and have worked on cars for about 20 years..Ive seen alot of wierd things and even came accross a pump that ran even with the car off..but I can't say 100% this is your problem..maybe if you can record the sound and put it up on youtube for us to hear..
 
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Steelcity

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I have a 2003 and it has factory air leveling suspension in rear and it even has an air outlet in back hatch area for inflating your tires and inflatable swim toys it even came with a long air hose and pressure gauge for inflating your tires.also look at this link (under suspension/handling)

http://www.cars.com/pontiac/montana/2001/specifications/?acode=USB10POV092B0

not to say it's not the fuel pump or spare tire rattling ,but these air shocks are known to leak cause the air bladder in them degrades quickly seen it alot on the park avenues and with the bad shocks you talk about ,that would mean the compressor is cycling on and off alot.
 

Roadrunner

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I have a 2003 and it has factory air leveling suspension in rear and it even has an air outlet in back hatch area for inflating your tires and inflatable swim toys it even came with a long air hose and pressure gauge for inflating your tires.also look at this link (under suspension/handling)

http://www.cars.com/pontiac/montana/2001/specifications/?acode=USB10POV092B0[/ur Either way her ride does not come with air ride..if it did she would not have shocks as she said..they only came with struts in front so shocks would only be in back and since she has shocks there is no air ride
 

old man

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I gues you could locate the fuses for the various suspects and pull them when the noise is occuring. If it stops you know you have located the problem.
And for full disclosure I started as a line mechanic in a GM dealership in 1954 till I bought my own place in 62 ran that for 30 years till retirement. I dont claim to be up to speed on the latest stuff but basic trouble shooting skills still apply most of the time. Don't mean to step on anyones toes.
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Roadrunner

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you could do that..but alot of the new systems are way more complex..If you pull a fuse it could shut down more then just one area..alot of them are intertwined..so just be cause a fuse is tagds for one thing it could shut down two or three..but still a good idea
 

KrystaF

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Well today I tried just turning the key to the on position without starting the ignition and waited. I still heard the humming and it seemed to last over a full minute and only stopped once I opened my driver's door. That is the weirdest part!

But when I was talking to my husband about it, he said we do have one of those air compressor thingies in the back to inflate tires and stuff so now I'm not sure what it is. And I thought he said our shocks needed replaced but maybe we don't have them?? I have no idea. We bought the van used two years ago from a dealer that goes to our church and he got it at an auction so I have no idea what the previous owner may have done or added or whatever.

The fuel pump does have me a bit concerned though since I know that's an expensive fix. I know we need to have our alternator tested and possibly replaced and we may have a misfire or two in the spark plugs and our brakes need new rotors but other than that, I couldn't tell you what all needs done. If I had unlimited money, I'd have a complete overhaul done on it and make it like new but I don't. We have four kids so that's where our money goes!

Thanks for the guesses though and if I ever do get it figured out, I'll be sure to let you all know!
 

Roadrunner

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yes! If you do have air suspension you don't have shocks..you have the air bags you could call them...and if they are bad like steelcity said it could be the compressor..but since you hear the noise when you put the key to on position it's most likely the fuel pump..so when you put it to the on position that means the noise you heard is the one you been hearing? I believe the compressor only comes on after the car is started aslong as it's working properly, not sure..but you have narrowed it down..and if your having misfires then the fuel pump makes sense.
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KrystaF

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Ok, update. I took a look at that picture then my hubby and I crawled under the van and saw the same thing under our left rear tire. We left the key in the on position and heard the noise again and got out and put our heads under there and the cylinder thing in the middle of that "U" shaped shield is vibrating. Also, when we take the cover off the air compressor in the rear of the van and hold down the off switch, the noise quiets a bit. So I think it is the compressor thing.

Now, the weirdest part is that when we open the driver's door, it stops but then it will start up again a bit later. I think this is because when the drivers door is opened, all the auxillary power is turned off (i.e. radio and vents and lights shut off). So if it's an electrical problem, that could explain it I guess. I still think I'm going to have my step dad take a look at the fuel pump when he does our brakes again to make sure but I think it is definitely the compressor.

Thanks so much for all the input! Sorry for the confusion. I really am car-tarded. LOL! And my husband's an IT, he does computers, not cars! Thanks again.
 
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