Need help finding out which pulley or bearing is on its way of going out on 5.4 ford engine. Beginning to make a small grinding noise and would rather fix now in driveway instead of on the road. Problem is I can't figure out where the noise is coming from. I've loosened the belt and wiggled each pulley, no excessive play in any of them.I've put a screw driver again each pulley, no vibration feeling up screw driver. Any other ideas I could use to figure this out? 2003 5.4 I'm pretty sure the pulleys are:Alt, pulley tensioner, water pump, A/C, etc

My guess would be the serpentine belt tensioner. Mine was noisy so when I changed belts, I changed the tensioner. They are only a few bucks.

Very carefully use a Stethoscope, it will pick up sound very well from each pully. The grinding noise could also be a water pump, alternator, power steering, etc. Does the noise change when you turn on the AC? could be the idler pulley.

I'd take the belt off and individually spin the pulleys. The culprit should be obvious. I would lean toward any idler or tensioning pulleys as being the problem.

Get a spray bottle of water and spray each belt and pulley separately. The one making the noise will quiet down for a few seconds and the water will dry up quickly. Not sure which one ? spray it again.

I also say stethoscope not the doctor's a mechanic's

Any tricks, strange noise under hood/ which pulley?

13 Replies

westend
Explorer
Jun 01, 2014
I've used the water spray trick for finding a bad pulley. I actually have a can of belt spray to use for this. One problem with the spray is that the tensioner pulley is fully capped on the 5.4 and is mounted onto a bracket, attached to the engine. You could put a stream of water onto it and it won't hit the bearing surface or shaft of the pulley.

Getting a garden hose on the pulleys to use a stethoscope or even a stethoscope would be difficult with my truck. There is not a whole lot of space in there.

A tensioner pulley bearing failure is easily diagnosed by removing the belt and rotating the pulley by hand.
Mootpoint
Explorer
Jun 01, 2014
ernie1 wrote:
Get a spray bottle of water and spray each belt and pulley separately. The one making the noise will quiet down for a few seconds and the water will dry up quickly. Not sure which one ? spray it again.

X2

Always worked for me.
Likes_to_tow
Nomad
Jun 01, 2014
4 foot section of garden hose is the best method of all
haydoracin
Explorer
Jun 01, 2014
If you don't have a mechanics stethoscope just use a piece of garden hose. One end to your ear and move the other end around to each pulley.
tpi
Explorer
May 31, 2014
With the belt off the pulley you may notice a gravelly feel when turning it. Briefly start engine (briefly!) without belt and confirm noise is coming from one of the accessories. Do a water squirt on the belt just to rule that out too.

If try as you might you can't really narrow it down, you could always replace the idler bearings as periodic maintenance-especially if you plan to keep truck a while. Proceed from there if that doesn't work-sometimes at the very beginning of failure the noises are hard to locate.
John_Wayne
Explorer II
May 31, 2014
Put your ear on the screw driver handle when it's on the pulley and you'll hear the noise.
scottykrug
Explorer
May 31, 2014

Be careful around the alternator as the stethoscope is metal and will be attracted to the metal pulley while the engine is running. Very loud when it gets sucked to a spinning pulley, don't ask how I know.
path1
Explorer
May 31, 2014
OP here...Thanks to everybody.
K_Charles
Explorer
May 31, 2014
I also say stethoscope not the doctor's a mechanic's
ernie1
Explorer
May 31, 2014
Get a spray bottle of water and spray each belt and pulley separately. The one making the noise will quiet down for a few seconds and the water will dry up quickly. Not sure which one ? spray it again.