Im having a problem of my serpentine belt slipping off. If the belt is on and if you rev it up to 2000-3000rpm you hear a squeal. This is on a new belt . I also see the tensioner rocking back and forth as u rev it up and down..Ran the car without the belt and it was fine no squeals at revs. Im suspecting the tensioner since it looks original and the car has 140k. any feed back? thanks

 

probably bad tensioner. SC3 or SC4?

 

If the tensioner is moving then it is time for a new one.

 

it is a sc400 and yes might be a bad tensioner..I also found that when u spin the idler pully it does not spin quietly. so I might have to get a new bearing for that

 

ahh dude get under the hood and rev the engine at the throttle body while watching your harmonic balancer. if the balancer moves back and fourth it is boned. ,my belt had a little slip in it when i bought the car and i thought it was the tensioner at first until i watched the balancer. i almost promise that is where the real problem lies. the rubber in the balancer rots out after about 15 years and it can shatter and destroy your engine.

 

yeah your belt is slipping off because when you rev it the balancer moves out away from the engine. causing it to pull the belt off the tensioner. do the test and let us know.
p.s. dont drive it!!!! fair warning if that balancer explodes it will very likely throw heavy metal pulley through some real expensive parts.

 

bump for the second opinion the op never saw.

 

Bleedspeed, I'm having the squeaking noise to. I've change the serpentine belt 6 months ago and still looks good. Change tensioner and idler pully and it stills squeaks. If I turn on ac, it squeaks even louder while driving. An autozone tech told me. It could be my altenator seizing up, causeing it to squeak. I don't know if that's was true. But if it comes down to it, I'll just go to Lexus and find out what's the problem. Any help would be appreciated thanks for reading

 

The 1UZ doesn't usually have the balancer problem. That is typically a 2JZ thing.

 

Its the tensioner allowing slack in the belt. I would check it again and replace if detected any slack.. Replace immediately if possible. Just my opinion.

 

ahh yes ehum good point! lol 400 duh. i failed to realize we were talking about a 400. cant help ya there guys. i believe if i remember right tensioner should be replaced every 60k miles.

 

300 or 400, rubber is rubber and if the rubber on the harmonic balancer is rotting it will cause excessive movement. Still, that doesn't mean that the tensioner is perfectly fine. make sure that all your pulleys on all your accessories are lined up and don't wobble around.

 

Sorry for the newb question. Stick3 where's the harmonic balancer? Where do I look? I have no idea how it looks like... Thanks for any advice

 

UPDATE. The bearing in the idler pulley was shot and thats why it was making that annoying squealing noise at high revs. I had that replaced and no more sound. also belt was not slipping off after. I still plan to change the tensioner soon and will look into the harmonic balancer. the harmonic balancer is the one that spins the fan right? correct me if im wrong

 

im sorry the very bottom one that connects to the crankshaft?