95 ohv engine knock - probably belt related

[sloop]

my 95 has a knock. more of a rattle than a knock. it ONLY does it at idle rpm when in gear (drive or reverse). when you accelerate, it stops. the belt tensioner is bouncing, so i replaced it. still have the problem.

it does not seem to be related to the a/c, but to how much juice the alternator is pulling. with the fan on high, the rattle is louder than when i turn down the blower.

about 180,000 miles on it.

can the alternator be causing the rattle? i suspect the rattle is the belt tensioner, but that is a symptom rather than the cause.

if i replace the alternator, any brand recommendations?

i read one thread where a belt had stretched and caused a noise so i will replace that, but i doubt it is my problem since pulling power increases the rattle.

i read the harmonic balancer thread and praying that is not the problem. i asked an alternator shop and another mechanic. each did the screwdriver/stethoscope thing but could not say for sure what the problem is.

thanks for any help you can give.

 

[eazuaje]

Sounds weird, try explaining a bit better. It's like a typing machine sound? a knocking sound? it goes away when you accelerate, try opening the hood and having someone hit the gas while you look for where the sound comes from. Does it comes from the engine? the fan? AC clutch? Power steering pump? you'll need to be more specific.

Eiber.

 

[sloop]

i found it. i had the sound narrowed to the belt tensioner, but after changing it i had the same rattle. the problem was a stretched belt causing the tensioner to rattle at a low rpm (idling in gear with stress on the alternator). turning up the blower would make the noise louder.

thanks to pontisteve in this thread:

http://www.explorerforum.com/forums/showthread.php?t=319067&highlight=rattle+belt

simple as that. surprising what a slack belt can cause. the belt did not have any visible signs of deterioration. the pictures of the belt tensioner indicator on the thread above will show you what a stretched belt will look like on the tensioner indicator and a correctly tensioned belt looks like.

for my engine (v6 ohv with a/c), i used the gates k060870.

thanks eazuaje - i had mechanics stumped too. ford even said these things can be a guessing game but i will know what to look for on a stretched belt now.

 

[eazuaje]

Any time Sloop, that's why we are here, a true desire to help; although, I didn't help much...

Eiber.

 

[96eb96]

Please replace your idler pulley as well. They are a failure point on these trucks an will leave you stranded if not addressed. It is a cheap fix that you have to do!!!!