Noise: "Squeak Squeak" on cold start

[sevenhelmet]

OK gents, a noise I'm at a loss to explain:

This started a few months ago, maybe longer. When I first start up the Jeep after sitting overnight, I hear a "squeak squeak" noise about 2x per second. The weird thing is, it's not related to engine or drive-shaft/tire speed- it sounds exactly the same when I rev up and start rolling. When I start driving, I can still hear the noise if the windows are rolled down, but it always goes away after 2 minutes. It's not loud; the just rolling up the windows mutes it. My Jeep has no issues with acceleration or shifting, and idle is smooth as butter. Went wheeling the other day with no issues. I'd just like to know the source of this mysterious squeaking mouse.

I'm thinking fuel pump maybe?? I don't have any good ideas on this one. The fact that it doesn't change when I rev and change gear has me stymied.

 

[sevenhelmet]

Nobody? Wow, I must have a good one here. I figured you guys would be all over this.

I will try to record it and post tomorrow.

 

[dude1116]

When was the last time you changed your serpentine belt?

 

[badkittystt]

I was thinking belt too, just because I've had a similar noise in the past, then the belt broke and killed my ac pump. It was sad. But I don't think the speed of the belt is affected by revving or anything, I could be wrong, but I think it's constant.

 

[TwoBobsKJ]

I've got a squeak like that on cold start - same symptoms, goes away by the time I back out of the garage. Mine seems to come from the engine compartment or firewall area though. I never thought about the fuel pump or any parts like that.

I'll listen more closely tomorrow morning.

Bob

 

[sevenhelmet]

It might be time to change the belt or the tensioner, I have a trail spare that I could try, just to see if it fixes things. But doesn't the belt spin up with the engine RPM?

 

[dude1116]

It might be time to change the belt or the tensioner, I have a trail spare that I could try, just to see if it fixes things. But doesn't the belt spin up with the engine RPM?

I was thinking that too, however would you really be able to hear a small squeak under the roar of a revved 3.7L engine? :smokin:

 

[trent.brown]

Belt definetly changes speed with engine RPM. Not trying to be a dick but, are you sure it doesnt speed up with engine rpm? I would think the belt would squeak about twice a second if the tensioner pulley bearing was going bad allowing the belt to wobble. Does your belt wobble slightly on the tensioner pulley?

 

[sevenhelmet]

UPDATE: This morning I started up, and got out to listen to where the noise is actually coming from. It is definitely coming from under the back of the Jeep, and it does not change at all when I rev the engine or start driving.

http://www.youtube.com/watch?v=8xVuU4zxSu8&feature=youtu.be


Check out the above video for the noise. I rev the engine first to 2000 RPM and then to 3000 RPM with no change to the squeaking.

So. Weird vacuum leak? Fuel pump on the fritz? Alien tracking device? I'm all ears, fellas...

 

[sevenhelmet]

Link to video added, see above. I couldn't get the embedded video code to work.

 

[TwoBobsKJ]

Dude, ya been holding out on us. Ya got a pair of crickets in yer trunk, right???:happy175:

That is funky. Mine sounds nothing like that and the sound is in the front. I don't know what the hell you got goin' on under your Libby but that is bizarre...

Bob

 

[sevenhelmet]

Yup, it's a weird one.

I crawled under there tonight and found a broken, dry-rotted vent line coming off the rear brake junction block. I installed a new line, but I don't see how that was causing the squeaking.

 

[Ry' N Jen]

When it stops going squeak squeak is when you need to worry!

J/K!

I'll go outside and see if our Rig makes a similar sound...
But for now I am also at a lack of ideas.

 

[sevenhelmet]

It stops on its own about a minute or so after I start up. The noise only occurs when the Jeep's been sitting overnight.

 

[Ry' N Jen]

It stops on its own about a minute or so after I start up. The noise only occurs when the Jeep's been sitting overnight.

Well I went and had a lay down under our Rig to see if I could visualize where
that sound may come from but so far I'm coming up blank!

Could it be an electronic sound that we hear on the video?
I'm just taking a wild card guess here.

 

[Paul M]

It's gonna blow Scotty! Good mystery. Sounds like a mount rubbing but doesn't change with RPM's, as if something is "on" and rotating. Here's a thought: fuel pump.

 

[sevenhelmet]

Yeah, fuel pump was a thought I had, too. Does it run at constant RPM? Listen to the video- just before I crank the engine, you can hear a whirring noise when I turn the key to "run". Isn't that the fuel pump?

 

[Ry' N Jen]

I've never heard the fuel pump in the last five and a half years we've owned our's.

 

[Paul M]

I've never heard the fuel pump in the last five and a half years we've owned our's.

So that begs the question: What could make a steady "squeak" that isn't affected by RPM's. My original thinking was the catalytic or a muffler mount or some loose metal item or spare tire mount, but that likely would change with engine speed or load or movement and wouldn't go away when warmed up. What else back there could make the sound? Seems it's not so elementary, Watson.:shrug:

 

[Porkchop]

Had a motor mount do this once after a lift kit was install took like two week of constant looking and checking at the right time to find it. So I would say get a long screw drive or a mechanics stethoscope and keep at it.