2007 5.7L squeal on start up - sometimes

[4x4 AG]

This issue is what lead me to this forum. I have been chasing sounds coming from my engine bay. First it started as a bearing going out kind of noise. So it lead me to believe it was the tensioner bearing going out. So I replaced it with a Rock Auto tensioner, Dayco, and that sound was resolved. But a new squealing sound started. It is only sometimes, and varies on the amount of time it last and loudness. Usually if you goose the gas it will stop. When i changed out the tensioner, i changed out the belt as well with a Dayco replacement. From the looks of it, the belt seemed to be slipping. So I changed to a Gates. Same sound was happening. So i researched and found that folks like the Goodyear Belt. So i ordered one of those. Still had the issue. So i pulled off the RockAuto Dayco tensioner and replaced it with a Toyota OEM tensioner. I am still having the issue.

So my question is, what else could it be? at this point i am thinking it cant be the tensioner or the belt, it has to be something else. Any ideas? Common problems i am missing?

Thanks for the help.

[4x4 AG]

Up. Need help diagnosing this.

[Tundra Hunden]

Originally Posted by 4x4 AG

This issue is what lead me to this forum. I have been chasing sounds coming from my engine bay. First it started as a bearing going out kind of noise. So it lead me to believe it was the tensioner bearing going out. So I replaced it with a Rock Auto tensioner, Dayco, and that sound was resolved. But a new squealing sound started. It is only sometimes, and varies on the amount of time it last and loudness. Usually if you goose the gas it will stop. When i changed out the tensioner, i changed out the belt as well with a Dayco replacement. From the looks of it, the belt seemed to be slipping. So I changed to a Gates. Same sound was happening. So i researched and found that folks like the Goodyear Belt. So i ordered one of those. Still had the issue. So i pulled off the RockAuto Dayco tensioner and replaced it with a Toyota OEM tensioner. I am still having the issue.

So my question is, what else could it be? at this point i am thinking it cant be the tensioner or the belt, it has to be something else. Any ideas? Common problems i am missing?

Thanks for the help.

Its possible the brushes on your alternator are dirty or worn. Have you been able to localize the sound? Is it left/right side etc?

[4x4 AG]

I haven't been able to localize the noise. As it is random and only last a split second to a couple secs mostly. So by time I get to the engine compartment it is gone.

[DeserTundra]

Where do you live? Most likely if the noise is at stat up and its cold outside its the power steering pump howling. Mine will do it if its colder than about -25C

[4x4 AG]

I am in Houston Texas, so that is not the issue.

I have changed out pulleys, and belts several times. I am at the point now that I think a drop or two of radiator fluid is coming out of the weep hole on the water pump and getting on the belt. 4 brands of belts, including the toyota one, cant all slip. that is all i can come up with.