[Foy]

Gents,
My truck started making an intermittant loud screeching noise from under the hood late last week. Simultaneous to the quarter- to half-second screech, I can feel a vibration--like whatever is causing the screech is causing a drag on the idling engine. It seems to do it only when not fully warmed up and the noise itself and the frequency seems to go away once the rpms are up a little, so when the truck is driven, the noise comes in at idle (stoplights, etc) but can't be heard when under way. The turbo sounds like it's spooling up normally when the truck is driven. The truck idles fine even when the noise is happening. The various pulleys/tensioners in the serpentine belt circuit seem to be "tracking" fine, and there's no smoke or other indication of pulley bearing failure. Yesterday I cranked it up and drove approx 15 miles to a diesel shop to have it looked at, and the noise stopped once I got up on the Interstate for a few miles (I'd heard it at the stop light before the Interstate but not once I got to my across-town destination).

My thinking is it's coming from the A/C (but switching the A/C on and off doesn't seem to affect the noise) or one of the pulley bearings, but it's very difficult to pin down exactly where it's coming from. I may need to leave it at the shop overnight so they can catch it cold, but I am interested in some input from the experts here before just dropping it off.

When I drove it for around 15 miles on Friday, I had the A/C off but had switched it on and off a bunch trying to see if the noise changed or went away. It was fully warmed by the end of that trip and was still raising Cain. Yesterday morning, I ran the A/C the whole time and the noise went away, making me wonder if that's the source. The A/C seems to be functioning OK.

Any ideas appreciated.

Foy

 

[chuckster57]

Take the belt off and let the truck sit overnight. Then hand turn each pulley and listen for a noise and feel for any resistance.

 

[RT]

And if all the pulleys feel ok - most likely your belt is stretched to the point where the tensioner can't keep it tight enough. Might be as simple as replacing the belt. I wouldn't pay a shop for that, though...

 

[Foy]

Good points, both

I've already got a replacement serpentine belt, purchased just before a long trip in December, a trip which came up to quickly for me to do the installation. I imagine the pulley bearings are like wheel bearings in that if they're bad, it's obvious when you spin the unloaded pulleys.

Update: I just cranked her up after a 24 hour park: No noise whatsoever. Drove around 10 miles, including Interstate speed, and still no noise.

The serpentine belt has at least 110,000 miles on it and is at least 7 years old, so it's time to change it regardless, eh?

Thanks for the help. I'll re-post following these and any other suggestions.

Foy

 

[Camshaft]

Check all your pullys (2 tensioner and 1 idler). You likely have some dry bearings here.

Then check your water pump for excess movement of the shaft.

Of course - do all this with the belt off.

I just replaced the water pump, belt, and pullys after about the same mileage on them and the idler was dry and the water pump was actually scraping on the inside. There is a lot more force in the belt when the truck is hot and the fan clutch is engaged - so that is likely why you get the screeching when hot and at high RPM usually - either belt slipping or idler screeching under load and RPM.

 

[Foy]

Will do

I'll definitely pull the belt and check the pulleys and water pump.

The odd thing is the noise STOPPED when warm and after having been driven a few miles. Earlier today, I cranked her up dead cold and no noise. Drove her about 30 minutes on a warm NC morning (mid-80s and humid) and still didn't get the noise.

Foy

 

[mustangii]

fwiw i had a simalar problem that started after a belt change and i tried a couple of belts. for some reason my truck only likes goodyear gator back belts put one one and all fixed

 

[Foy]

UPDATE- Water pump failure

Gents,

I fired her up yesterday to change position in the driveway in order to have some shade to change the serpentine belt today. I noticed around a quarter-inch of belt side-to-side travel on the water pump pulley, movement which matched the noise. Cranked it up this morning and noticed the fan deflecting coincident with the noise. Reaching down w/ the engine shut down I could move the fan/pump around readily.

New water pump, belt tensioner assembly, idler, and serp belt going in next week. All Motorcraft-supplied parts (where my diesel shop does enough business with Motorcraft to get a good price). All of the noted parts are, to the best of my knowledge, OEM, so at 10 years of age and 206,000 miles, I'm going to go ahead and change it all out. Luckily we managed to catch it before total failure and destruction of the radiator, shroud, etc.

Thanks for all the help.

Foy

 

[jpciron]

Foy,
How did your problem start? I have been trying to track down a similar issue. Mine squeeks when I shut the truck down somtimes and other times not.
Thank you
JPC

 

[Foy]

Foy,
How did your problem start? I have been trying to track down a similar issue. Mine squeeks when I shut the truck down somtimes and other times not.
Thank you
JPC

JPC- I cranked the truck up Friday of last week to hitch up to my utility trailer for a trip to the landfill and heard a loud, intermittant "chirp" and "screech" sound, coupled with enough sudden vibration coincident with the sounds to worry the crap out of me. I could sit in the cab and feel the sudden "thunk" right through the steering wheel, and when over the idling engine with the hood up, I could feel it through the fender I was resting my hands on. As I think back on it, I probably heard something on widely-spaced intervals for a few weeks before last week. The truck is not a daily driver, and I faintly recall hearing "something" on occasion but never persistent or loud enough to cause alarm like it did on Friday.

Even when it started the noise on Friday last, it would come and go, and initially I could not see any odd behavior from the way the serpentine belt tracked an any of its driven or tensioner or idler surfaces. The experienced diesel shop guy saw no belt deflection on Monday of this week, either. Only after I drove it more yesterday did the noise become more "on" than "off" and the vibration got worse. Late yesterday I noticed the belt tracking oddly on the water pump pulley, and this morning I noticed the fan deflection and was able to "wiggle" the whole water pump assembly by yanking on the shaft. It did not leak a single drop of water through the whole sequence of events.

Hope this helps.

Foy

 

[jpciron]

Thank you Foy
I will do more digging around on mine. I hope its not the water pump. Glad it didnt leave you on the side of the road. Good luck with the repair.
JPC