Strange noise from under hood

I'm hoping someone can help me. Recently I've noticed a noise that kind of sounds like a bad throw out bearing, its coming from under the hood. Sort of sounds like diesel engine. It does it for about a minute or so when I first start it up after sitting a little bit, then goes away. Could it be a bad bearing in water pump or alternator, maybe idler pulley? How do i know where its coming from, hopefully not the engine.

How many miles on the engine?

Idler pulleys are notorious for early bearing failure, pull your fan belt and turn all the driven pulleys by hand, an easy check that narrows it down.

Timing chain tensioner could be going bad.

EasyRhino said:

How many miles on the engine?

Idler pulleys are notorious for early bearing failure, pull your fan belt and turn all the driven pulleys by hand, an easy check that narrows it down.

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Right about 256000 miles. Thats right , not a miss print. Got alignment and tires last weekend and was at 255224 miles. Runs great same engine and trans no problems. If it was pulleys wouldn't it do it all the time? Thanks for advise, I'll check them, to see. i guess I'm looking for wobbling or weird sounds while spinning it?

matt0248 said:

Timing chain tensioner could be going bad.

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Just like the pulleys , wouldn't it make noise all the time or every time I start it? It only does it when starting and only occasionally. Then goes away after a minute or less. Do I have to pull apart front of motor to check this or is there an easier way, probably not huh? Its just really hot here right now, lol.

When off and sitting, the oil drains down into the pan, so when starting up there is very little coating the moving parts, until the pump starts to circulate it. generally a noise like that is related to lifters or worse, rod bearings or wrist pins. When dry there's enough slop to make the noise, then the oil gets into the space and quiets it. Not surprising with that many miles, but you might be able to stretch it with a coating additive such as STP, Slick50 or Restore, or switching to a thicker oil. Whatever it is, that sound is metal on metal and starting it 1-2 or more times a day will make whatever it is wear out a lot faster from now on.

Hi guys,
i dont mean to hijack the thread over here, but i'm having the exact same problem on my 2003 xlt with 100 kMile. i'm suspecting the alternator to have bad bearing, any way to tell?

A good way to see if its belt or pulley related is to pull off the belt. Start it up and if the sound is gone you know its a pulley, if its still there then you know its internal. Just don't run it very long, you wont be charging the battery or more importantly running the water pump.

thanks Sport97, to be honest i thought of removing the belt but found no article on how to do that. spraying WD40 on the alternator axle might be an option?

another way after the engine has been running for a bit spray the pulley's down with a little water, small spray bottle as it doesn't take much, and see if one is running hot. When my idle pulley went as soon as i hit it with some water it boiled right off. . .

jrford said:

another way after the engine has been running for a bit spray the pulley's down with a little water, small spray bottle as it doesn't take much, and see if one is running hot. When my idle pulley went as soon as i hit it with some water it boiled right off. . .

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nice idea, i'll try it soon and update.
BTW, the exact case is as follows: the grinding-like sound comes only once i start the truck and even not always, lasts for like 3-4 seconds or sometimes as a maximum for 30 seconds. if turned off and started again immediately no noise is there. i noticed some slight bearing noise from the alternator side.
i took it to a workshop, changed the idler, tensioner, and belt, still the same.

i'm thinking of changing the alt bearing, any good article for that (at least how to remove the drive belt)

thanks.

i got the 4.6 but its essentially the same (at least the fords ive seen), is take a 1/2" wrecker bar, there should be a square hole in the arm of the idler pulley (spring loaded) which it fits into. Very tight fit on my v8, but it will go in and you push on the bar to take the slack out out of the belt. . .

Last i heard the Alt bearing isn't a typical user replaceable part, you have to buy a reman/new alt to get it. Unless you own all the tools to take it apart, might as well do the brushes too. . .

I noticed you have the V6, before you doing anything major, read up on 'timing chain rattle', very common in the v6. alt bearing noise is more constant whine or squeal

The water pump to can make noise but almost all the time, it can make a grinding noise however. Remove the belt turn by hand and it should be stiff but smooth, no play or looseness.

But those timing chains, . .startup rattle common. . .

sounds like bunch of money for the timing chain if gone bad?
however, i'll remove the belt and fire up to confirm an internal issue.
for belt removal procedure, seems i dont have to loosen or unscrew any thing, it's just pushing the tensioner away, and installing the belt is the same way, correct?

essam said:

sounds like bunch of money for the timing chain if gone bad?

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yep, might want to check the 2nd gen forum for specifics

essam said:

however, i'll remove the belt and fire up to confirm an internal issue. for belt removal procedure, seems i dont have to loosen or unscrew any thing, it's just pushing the tensioner away, and installing the belt
is the same way, correct?

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That was the way on my v8 should be the same on the v6, but not 100%

BTW, if it is the timing chain, wouldn't the noise be permanent? i'm having the noise only some times and for less than 5 seconds. does it sound like any thing familiar?
is there any other symptoms for bad timing chain?

essam said:

BTW, if it is the timing chain, wouldn't the noise be permanent? i'm having the noise only some times and for less than 5 seconds. does it sound like any thing familiar?
is there any other symptoms for bad timing chain?

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Not always. THe timing chains use spring and hyrdaulic tensoner in one assembly. Oil pressure is used to push the tensioner against the timing chaing to take up any slack. when oil pressure is low, and if the internal spring is weak the timing chain could be ratttling for a few seconds until oil pressure has raised. This will happen especially after the engine has been off for a long time and the oil has drained out of the tensioner.

UPDATE:
turned out to be the rear timing chain cassette. had to remove the engine to replace a 10$ piece of plastic.
costed around 1500$ at the dealer.

essam said:

UPDATE:
turned out to be the rear timing chain cassette. had to remove the engine to replace a 10$ piece of plastic.
costed around 1500$ at the dealer.

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Ouch...I've got a similar noise that I believe to be timing chain tensioner related. Any drawbacks to just living with the annoying noise?

Doomstang said:

Ouch...I've got a similar noise that I believe to be timing chain tensioner related. Any drawbacks to just living with the annoying noise?

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unfortunately, if you've got a broken cassette, the chain could jump anytime and toast the engine. you'll end up needing to change the whole thing instead of the chain only.