Rattling/tapping noise just appeared, coming from engine bay.

So I just started hearing this noise in my taco while going through the drive thru. Any idea what It could be? Never heard it until today. Maybe belt is old? Or something is tapping. Hope it's nothing serious


https://youtube.com/shorts/Zye5znlKM0A?feature=share
https://youtu.be/-znVjje9WxU

 

Does the sound change with engine speed?
Maybe pull the belt off and see if the noise is still there?
Obviously, you don’t want to run the engine long. But that’s how I’d start my diagnosis.

Well actually I’d do a visual inspection first. But that’s obvious.

 

A/C running? Sounds ancillary to me, I'd check the A.C first if you had it running. I'd also check your tensioner pulley's but it sounds bearing related to be, one is failing.

 

So I found a thread where someone had the exact same noise and it turned out to be a belt tensioner. So hopefully that's the case. I'm about to take my truck in for further diagnostic and update this thread.

 

So upon further inspection, the noise only occurs with the AC running and the AC clutch spinning. Is this most likely an AC compressor fault or perhaps the belt tensioner adjacent to it is bad? Thoughts?

 

I'd start with the tensioner simply because it is far cheaper then an A/C issue but you should be able to feel a bad bearing in a tensioner. Does the noise go completely away when you turn the A/C off?

 

Remove belt and check each pulley/bearing. They should all spin smoothly. The idlers, water pump and tensioner should have no play of side to side and no in n out play. The PS can have about 1-2mm of in out play, but I don't know about the AC pulley/bearing.

 

https://youtu.be/V418wOYshCI

So this is basically what is happening to me, ac kicks on and the noise starts. Otherwise just normal taco ticking. Not sure how the AC kicking on causes the tensioner to start rattling but probably due to the fact that it's directly adjacent?

 

When the AC kicks on, that puts added strain on the belt and that could be just enough to cause one of the bearings to start howling. Or, it could be the AC bearing. The pulley/bearings adjacent to the AC, belt wise, are the #1 idler and the alternator. If the pulleys are in good condition, you can replace just the bearings inside them. Relatively easy to do on the idlers and tensioner, more difficult on the AC, PS, alt, and water pump.

 

I just dealt with this issue and it was the A/C clutch. I purchased an automotive stethoscope for like 15 bucks and it was worth it to pin point the sound