Weird Noise From Engine That Goes Away After A Few Seconds

[jamesbeat]

NOW WITH VIDEO - PLEASE SCROLL DOWN TO POST #9


I recently had a problem where my Jeep Liberty (2003, 3.7l, 130,000 miles) stalled and then made a loud rattling sound.

I traced the problem to a bad belt tensioner and PS pump, which I have now replaced.
It stalled again, so I took it to Autozone. No codes, and battery and alternator are fine.
I replaced the spark plugs and PCV valve and did an oil change for good measure and it hasn't stalled since.

I have noticed a sound coming from the engine when I first start it.
It's entirely possible that this has been happening for some time, and I only noticed it because I have been paying close attention to that area recently.

When I first start the engine, there is a sound from the front of the engine.
As part of my diagnostics for the above problems, I have run the engine without the drive belt, and the sound is still there.
This rules out an accessory making the noise.

The sound seems to be coming from the bottom front of the engine, although it is hard to pinpoint.

It sounds a bit like when you rub a wet finger around the rim of a glass (but much louder obviously).
It lasts probably around 20 seconds, although I haven't actually timed it. It happens whether or not the gearbox is in drive.
When it stops, it goes away abruptly, as if it is being turned off.

Is this a normal sound that I have just never noticed before?
Any ideas what it could be?

 

[HoosierJeeper]

Does it happen only on a cold start? Does it get louder with RPMs?

 

[jamesbeat]

Yes, I believe it is during cold starts that it happens.
However, it's not really loud enough to make out when I'm inside and the hood is closed.

I have to be outside the Jeep to hear it, and I can hear it much better with the hood open, so it's possible that it's happening all the time and I just can't hear it.

I'm afraid I don't know if it changes with rpm's because it has usually stopped by the time I get the hood closed and into the drivers seat.

 

[Conundrum2006]

If it's just at cold start up it might be a fairly normal sound depending on the age and miles. The engine timing chain tensioners getting oil and the lifters, they are a little dry at first start up.
A better oil filter might help if it's just start up noise but it's hard to say that's what it is.

I have a f150 that made a lot of noise at start up then sounded ok (until warm) the chain tensioners were gunked up and the plastic guides for the chain had broken allowing a lot of chain slapping noises at start up, it was an extreme case and the motor didn't last much longer. It also sounded like Diesel at operating temps because the ford cam phasers were a garbage design.

Apples to oranges comparison, but depending on the sound some noise could be expected, it also could be a bigger problem.


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[HoosierJeeper]

I'd think if it were tensioners it would be more of a tick.

 

[Conundrum2006]

If it's not in the accessories.... and not a tensioner or lifter, could be in the bottom end.
I'm not clear on what kind of sound it's supposed to be. High pitched? rhythmic ?
And Something that goes away abruptly. Possibly transmission, flex plate or torque converter bolts.
Ordinarily my first thoughts would be accessories. For a brief sound tensioners and chain slap.
Harmonic balancer? Could that make the noise?



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[GunnerSchenck]

Yes, I believe it is during cold starts that it happens.
However, it's not really loud enough to make out when I'm inside and the hood is closed.

I have to be outside the Jeep to hear it, and I can hear it much better with the hood open, so it's possible that it's happening all the time and I just can't hear it.

I'm afraid I don't know if it changes with rpm's because it has usually stopped by the time I get the hood closed and into the drivers seat.

You can raise the rpms from under the hood when it's happening to see if it increases with the rpms...

 

[ltd02]

I'm afraid I don't know if it changes with rpm's because it has usually stopped by the time I get the hood closed and into the drivers seat.

You can raise the rpms from under the hood when it's happening to see if it increases with the rpms...

Just rotate (counterclockwise) the arm on the side of the throttle body (where the throttle cable attaches) while you are under the hood. Then you'll know. Tip: don't wear a tie.

The secondary tensioners can take a bit to pump up but that was a clear chattering noise when mine were failing. I'd be thinking of a failing front crank seal (you'd probably get a leak first though) or worst case, a bearing(s) going with little or no oil for a bit. That would not be good.

 

[jamesbeat]

Thanks for the help so far, but I guess you would find it easier if you could actually hear the sound!

I recorded a video just now.
I'm afraid the camera on my phone is terrible in low light, but the sound is the important part.
Ignore the bang at the start, it was just me banging on the fender to signal to my wife to start the engine:

https://youtu.be/fmx_eNfLIv4

The sound starts about a second or two after the engine catches - its a little difficult to hear it over the engine sounds, but it's the constant tone in the background. It's a little quiet in the video (perhaps because the Jeep was driven around three hours ago) but it is often quite a bit louder.

I got my wife to blip the throttle twice, and it does not appear that the quality of the sound changes.


I didn't record long enough for the sound to stop, but it lasts maybe 20 or 30 seconds and then stops.

Just a reminder - this sound happens even with the belt removed, ruling out the accessories as the cause.




ltd02, I don't think there is any oil leaking out of the front crank seal (that would be the area around the harmonic balancer right?) but I can't be 100% sure because I have a leaking rocker cover, so there as always a bit of oil around.
I've been waiting for the weather to get nicer before replacing the gaskets.

 

[GunnerSchenck]

Not sure which sound you mean.. if you mean the sort of humming sound, is your heat on? Defrost perhaps? If so, try it on a few cold starts with the heat setting in the off position and see if the sound is still there.

the following is for if you mean the chittering sound..
Could just be the recording and the sound be normal in person, but in case I'm hearing it right..

Definitely an odd sound.. not quite a click, chatter or tick..
I saw you said you changed the oil but didn't state how lon ago it was, have you since checked how much oil I'd in it?

When you replaced your spark plugs did you make sure that your coils were seated on the plugs properly before tightening them down? Almost wanna lean towards one of them not being seated properly, especially if the sound started after doing them.
But then again I'm just hoping for an easy solution for you.

I'd take advantage of this break in weather we're having and pick up some valve cover gaskets and hop on that job. It's pretty quick and the drivers side is even easier than the passengers.. all in all about a 3 hour job for both sides. 5 if you're unexperienced, less than 2 if you've done it before..

When you end up getting around to that job though, definitely a good time to inspect your lash adjusters, rocker arms, etc.. if you don't know what to look for, plenty of good info on here.

 

[LibertyTC]

I would like to take an auto stethoscope to and around the water pump area, and assume it possibly could be from the timing chain with a sloppy tensioner?

 

[dhula]

I'm guessing you are asking about the sound like a tuning fork humming

(if I had any kind of musical skill I'd be able to say - That's a High G - but I don't so have no idea what note it's playing :icon_razz: )

to me it sounds like something vibrating or perhaps a pump cavitating.
I don't know anything about the V6, is there anything else apart from the water pump that is directly driven from the engine (ie, not from the fan/accessory belt)

I'm assuming you've checked fluid levels in everything that turns when the engine starts but if not, maybe double check to be sure

 

[jamesbeat]

Yes, it's the tuning fork type humming that I'm talking about.

Definitely not the water pump, as that was ruled out when I removed the belt.
I have replaced the spark plugs and changed the oil, but the sound was present before either of those, and has not changed since doing it.
Oil level is exactly on the maximum mark.
Transmission fluid has been drained and filled three times, so it is at the correct level and is around 60% new.

 

[jamesbeat]

I've been thinking about this some more, and maybe it will help if I make a list of what we know:

The sound seems to be coming from the front of the engine.
It is not caused by an accessory, because it is still present with the belt removed.
The sound starts a second or two after the engine catches.
The sound lasts 20-30 seconds and then stops abruptly as if it is being switched off.
The sound remains the same whether or not a gear is engaged.
The sound remains the same when the engine is revved.

What parts rotate/move at the same rate independent of engine speed?

Is it possible that it just sounds like it's coming from the engine?
Could it be something else, such as the radiator fan?

 

[HoosierJeeper]

Could be the efan, try disconnecting the plug. If you have the mech fan too, it wouldn't have been spinning when you took the belt off.

 

[jamesbeat]

I'm going to feel pretty dumb (but also VERY relieved) if its the fan.
I don't have a mech fan, just the standard electric one.

Does the fan come on every time you start the engine?
I was under the impression that it was temperature controlled and only came on when needed.

Are there any other things that spin when the engine is on but do not vary in speed with the engine?

 

[uss2defiant]

possibly the AC compressor when the clutch kicks in.

 

[HoosierJeeper]

I'm going to feel pretty dumb (but also VERY relieved) if its the fan.
I don't have a mech fan, just the standard electric one.

Does the fan come on every time you start the engine?
I was under the impression that it was temperature controlled and only came on when needed.

Are there any other things that spin when the engine is on but do not vary in speed with the engine?

It could come on for a few seconds until it realizes it's not needed. It's hard for me to tell on the KJ since it has the mech fan that's always going, but my WK had the single efan and it sometimes would come on when I'd start it, especially if the AC was on.

 

[jamesbeat]

possibly the AC compressor when the clutch kicks in.

The AC compressor works off the drive belt - I already tried taking the belt off and the sound still happens.
This rules out the AC compressor, power steering pump, alternator, water pump, tensioner/idler pulleys as the cause of the sound.

 

[jamesbeat]

It could come on for a few seconds until it realizes it's not needed. It's hard for me to tell on the KJ since it has the mech fan that's always going, but my WK had the single efan and it sometimes would come on when I'd start it, especially if the AC was on.

That certainly makes sense, and a bad bearing in the fan motor would make a sound that appeared to be coming from the general area where I'm hearing it.

Are there any other rotating components that do not vary with engine rpm?