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2004 Explorer: making a loud rattling noise coming..first my mechanic

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i have a 2004 Explorer & it is making a loud rattling noise coming from the front right side of the motor. At first my mechanic thought it was the lifters making noise, but as i listened to it, it didn't sound like the lifters. Then he said he thought it was the timing chain, but agan as i listened to it, it didnt sound like the timing chain. It sounds more like a bearing going out, like the tensioner pulley or alternator bearings to me. Any thoughts? The motor has about 156,000 miles on it & has not had any major engine work on it, except a transmission repair, thanks, Tony.
Welcome Tony,

Does it tend to make the noise more on first start up or after warmed up

Or all the time.

Does the engine speed change the dB or rhythm when increased or does it stay the same all through out the engine rpm?

Customer: replied 4 years ago.
it seems to change a little bit as the rpms go up& down, but not drastically.
Thanks for that info,

That would indicate and verify the most common reason for this noise and you are right on track Tony.

If it still makes the noise with the AC off we can rule out the AC compressor #10

BY FAR the most common pulley bearing that is about to fail is the drive belt tensioner pulley # XXXXX It endures more tension than any other tensioner.

Now there is a chance that the belt idler pulley is at fault but i could only be certain by the sound....i can tell them apart like the front and back of my hand but not online...its just that the drive belt tensioner is under much more tension and fails the most.


Best wishes my friend and if you have any further questions feel free to reply

Now if the noise only happens when the AC compressor is engaged then the front compressor clutch bearing is bad so you need to pay attn to if the AC compressor clutch is engaged when the noise is happening.

If you have any further questions feel free to reply.

Customer: replied 4 years ago.

so how Larry, how can i determine which tensioner it is? by putting some kind of listening device to it? or by-passing it with the serpentine belt?


Here is what i use but you have to be careful because the engine and pulleys will be turning.

1. Use "Mechanics ears" a stethoscope kind of device and place it on the bearing housing BEHIND EACH PULLEY where the bearing would ride in the case, do not touch the pulley because there is to much noise.


2. You can also use a long handled screwdriver and use the screw end to place around the suspect area and then using your thumb, hold it over the plastic end of the screwdriver handle then place the handle and thumb to your ear.

3. A cut down wooden broom handle or smaller diameter of wood dowell will work the same.

By using this method i guarantee you will hear an area that is louder than the other pulleys and you have found the culprit...just be careful you dont stick that screwdriver or wood into the fan blade.

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