1999 4.0 "Bird Chirping Sound" What is it? Help!

[stonerboys]

Hey guys I need a little help, I have a 99 Explorer Sport with the 4.0 OHV V6 in it and its making this loud sound that sounds almost like a bird chirping that seems to be coming from one of the back 2 cylinders on the passenger side valve cover. Its not too bad at idle, but when you drive it it gets really loud. It makes several different, high pitched squeaking sounds. I'm thinking that its maybe a rocker arm or lifter making noise? Do these motors have roller rockers in them? My explorer is about to turn over 143k miles, but im afraid to keep driving it with it making this noise. I appreciate any help you guys can provide me with. Thanks!

 

[rb142]

I'm thinking cam synchronizer.

 

[fordfrystak]

Mine has been making the same "chirping" sound also. I noticed that it goes away after driving for a few minutes and letting some oil splash around. The cam sync is really burried in the back under the firewall. I have about 111,000 miles currently

 

[bill06447]

Check the fan belt idler pulleys first. Take the belt off and give each a spin/wiggle. If you have to think about if its normal for more than a half second, it probably isn't.

Bill

 

[rb142]

If in doubt about the pulleys, just leave the belt off and run the engine for a few seconds. That will tell you right away whether it is one of the pulleys (or belt) or not. It's definitely worth checking. But if the noise is clearly from the back, I would still go with my first answer.

You can narrow it down some more with a stethoscope (or an improvised equivalent, such as a long screwdriver or a piece of copper tube). Sounds can be hard to pinpoint under the hood.

Let us know what you find.