Weird rattling in engine bay

Started my car today to hear a weird rattling. I looked but couldn’t see anything out of place. The belt looks shaky.

 

Is the belt turning unevenly a problem?

 

I had a weird rattle that I couldn't locate until one day I noticed that I was missing a bolt on the driver side of the engine where there is a large bracket near the PCV valve. I only had the top bolt so the bottom was loose and would vibrate/rattle at certain RPM's. Bolt circled in RED.

 

Look at all the pulleys and tensioners as they spin to see if you see anything weird. Look at the edges of the belt for any fraying. Fan wobbly?

 

Take that top bolt off and go to Home Depot to match it. They are the same. I remove that bracket when changing spark plugs.

 

Pretty much exactly what I did to get a replacement.

 

So the sound only happens when I have the A/C on.

 

Sounds like you might have a failing belt tensioner/bracket when the AC comes on the serpentine belt system has more resistance than the tensioner can account for causing the belt to jump and slap.

Definitely verified and replace the tensioner if so as a slapping belt can cause your AC to stutter and shear the compressor/pump shaft.

Try throwing some water on the AC pulley while it's turning and if the AC light starts blinking on the button and the AC stops blowing cold it's definitely slipping and not in the "worn out belt" way if there's no squeal.

 

I have a 1grfe 4Runner with 150k. Had a strange rattle when idling which occurred only when turning the steering wheel. I initially thought PS pump but used the stethoscope and determined it was the tensioner pulley bearing. Connected a bunch of extensions to a bucket which acted like a speaker.

With 150k I decided to replace all of them. The tensioner solved the issue. Had no idea How much noise the pullies were generating. Twice now my vehicle had come and gone without me hearing from the house after replacement.

FYI if it's the tensioner. Not a lot of options for replacing just the pulley or bearing. I ended up replacing the entire assembly with the Gates tensioner. Took about 2hr and requires the Alt and AC compressor to be disconnected and fan to be removed. Unfortunately the Gates pulley cannot be swapped on the Toyota tensioner since the offset is different but I'm glad I put in the new tensioner. If you go Gates also note that the tensioner pulley bolt is 13mm vs the OEM 14mm. In hindsight I wish I would have gone OEM since I found one via Toyota parts online for $20 more than the gates.

Good luck, keep us updated.

 

https://youtube.com/shorts/FxOFM8HsvxE?feature=share

this look normal?

 

Actually, there's a great option for replacing just the bearing. Buy a Nachi 5203-2NS, it's a perfect replacement for the factory bearing in the tensioner pulley. Note that the bolt on that pulley is "righty loosey" (loosens clockwise). Just did this replacement on my Taco, easy peasy.

Now, if the tensioner itself is the problem, just buy the full OEM replacement bracket which includes the pulley. Makes the job more of a pain but it's well-described in a couple of threads here on TW.

 

Hard to tell on video but that crankshaft damper pulley looks kinda wobbly like the rubber has separated.

 

https://youtube.com/shorts/W_TngD44Oz4?feature=share

https://youtube.com/shorts/I3mzrcUjAdM?feature=share

here’s a better video. The sound comes on as the pulley on the right comes to play.

 

I think as a first step I'd pull the belt off and check all the pulleys for play and noise, and check the tensioner arm for play.

 

I’ve never worked on this before Anyone have a write up?