Intermittent clicking/rattling in engine bay

So, I know it could be a valve but it isn't a constant steady noise. Sometimes it stops completely and I'm thinking it is actually a pulley, whether it is idler or A/C clutch, or power steering pulley. I suppose it could even be the balancer pulley and I'll have to remove the belt and check all the pulleys to see if one is loose or wobbly or turning hard. Have any of you experienced that noise from a pulley instead of a whine when the bearing goes out in a pulley. This just started up out of the blue and I haven't had check engine or any issues with overheating. I don't see the fan interfered with and the fan shroud hasn't shifted. I also don't see any fraying or weird wear on the belt but I'll get a better look when I pull it. Is there a trick to isolating the noise? It really doesn't sound like a valve as it is way too loud and it sounds like it is in the front coming from the cooling fan/serpentine belt and pulley system.

 

there are no cooling issues so I don't think it is the fan clutch. However, when the engine is off the fan does turn manually. Is that normal?

 

Checked to see if any exhaust heat shields are rattling?

 

Thanks Skrain! I didn't even think about that. Now that you mention it, the exhaust has had a vibration when I accelerate hard. I will take a look at those and check them. . .after the truck has been sitting, of course

 

can remove the belt and start it.

 

Remove the belt and start the truck? Why would I do that?

 

To isolate the idler/accessory pulleys from the balancer? I do work on my own vehicles and have done engine swaps on older vehicles but I'm not a professional mechanic. my gut says firing up the truck with the belt off isn't a good idea. Are you saying fire it up for a moment to isolate the noise?

 

I suppose the only necessary thing not running would be the water pump but if the engine is cold and it's only on for a second it shouldn't harm anything

 

Correct. Water isn't circulated till the Thermostat reaches 180+ f anyways.. so you can run it for a minute or two (as long as your battery is healthy)

 

Thanks, wheeliest. . .Yeah, my battery is charged. I'll try that tonight and just make sure all the electrical accessories are turned off. . but only a minute or so won't kill it anyways

 

check air inlet hose that supplies air to filter. The hose is on passenger side fender. The insulation wears where the hose enters the fender and rattles.

 

Beerline123, thank you for the advice. I have an AFE aftermarket cold air intake so I don't think that is the issue, but I will check there as well

 

My exhaust manifold shield was held on by one weld, it rattled like the Dickens. I pulled it off, and will re weld it in the future. Good luck to you

I had a rattle when I first bought my truck that sounded like a knock on start up or when pulling. Turns out that my cold air intake was hitting the heat shield that it passes through. I centered the piping and have had no more word noises.

Squeeks, and very light rattles can point to idlers and are super easy to replace. To check put a 14mm wrench on your tensioner, and pull the bell off the power steering pump. Then spin each idler to find the bad ones. Buy OEM Toyota replacements.

Good luck