Weird sound when revving a little

[explorer_kalle]

Hey guys!

My dad has a 99' 4wd 4.0sohc explorer with about 130k miles on it. Nothing out of the ordinary done to it lately (well the back window is gone thanks to the lawn mower flinging a rock at it), all the fluids are fine, but when it revs to about 1500 rpm and above, there's this weird noise coming from it. It doesn't seem to be tied to the engine speed directly, it does increase in sounds per second when revving to 2000-3000 but then it dies off, ie it's seems to not be a valve lifter or similar.

A clip of the sound can be found at: http://youtu.be/Kt0XjxaG3Hk

If anyone has any idea of what it could be it would be a lot of help!

Thanks for your time,

Kalle

 

[t103190]

Timing chain noise maybe? Have they every been changed?

 

[2000StreetRod]

remove serpentine belt

I suggest that you remove the serpentine belt and run the engine for less than a minute. If the noise persists then its internal. If not, possibilities are belt tensioner, belt idler pulley, water pump, alternator, power steering pump or A/C compressor. It sounds internal to me but not the normal timing chain rattle.

 

[explorer_kalle]

Hi!

Thanks for the replies, took me some time to do something about it but I just removed the serpentine belt and the sound was still there. I went under the car and tried to localize the sound and it sounds like it's coming from the front end of the engine block. I have no idea when the timing chain has been replaced, surely not within the time we've had it (since 06). I live outside the us and there aren't many or any at all shops around here that know squat about these cars so taking it to the shop hasn't yielded any real solution. Should I perhaps check the timing chain tensioners to see if they are worn out and replace them if they are and if they aren't just proceed to changing the timing chain? How long do they last anyways?

Thanks for all the help! Much appreciated

 

[2000StreetRod]

balance shaft chain tensioner?

I listened to the video again and I think you may have a failed balance shaft chain tensioner.

It's unlikely it would have failed and been replaced by 2006 but very possible it has failed by now. Unfortunately, in order to replace the entire assembly the block cradle must be removed which is difficult to do with the engine in the vehicle. However, you can determine if it has failed by just removing the front timing cover.