Can't Stop Alternator Belt Screeching

[Wacky Dee]

Had my belts replaced a few months ago and shortly after .. the alternator belt started screeching on cold starts despite being tightened twice after the initial break in period.

So I took it back to Unigroup who replaced all belts with genuine Nissan ones. The new alternator belt from Nissan started screeching 2 days after install which was expected (as they stretch out a bit) so I tightened it a bit and it stopped.

But now again, a week later it's screeching on cold starts. If I tighten it any more it will be 'too tight' aka. I might risk damaging my bearings.

I mean what the f**k ? Has anyone run into this issue before ? Any way to fix other than continually applying that belt dressing crap or overtightening the belt?

[Wacky Dee]

just reading the '100k service' thread and noticed people mentioning that idler/tensions bearings should be changed at 100k service.

I've done the 100k service when I got the car (even though the odo said 65000, which I'm 100% has been wound back) but the idler/tensioner bearings were the only things I didn't get done.

Do these have anything to do with the alternator belt and could they (due to old age) cause belts to squeal even with the right amount of tension?

[PUDZ 32R]

i would put money on a rooted tensioner bearing mate. doesnt matter how tight u make the belf. if u keep driving like this u will just stuff the new belts.

i replaced all my belts with gates racing blue belts. mint belts. designed to run a bit tighter than standard.

u can get them from supercheap for bout $30 each.

[Wacky Dee]

well ..it does matter, because if I tighten the belt nice and tight it stops screeching .. but that's tighter than it should be. Is this the "tensioner bearing" for just the alternator belt ? (is there more than one tensioner bearing in there??) that you refer to and is there any way to confirm it's the bearing that's kaput? It only does this when the engine is completely COLD on startup..

[PUDZ 32R]

haha no i meant if the bearing is rooted it doesnt matter how tight u make the belt it will still screech.. not it doesnt matter normally because it does.

it would do it when its cold and not hot because it heats up and the metal expands loosening it all up therefore no squeaks.

i am thinking now that it is water pump bearings or alternator bearings sorry thought u said air con belt was screeching.

my bad didnt read ur post properly

the tightening the guys did may have triggered the bearings to go.

waterpumps dont cost that much

[DAS KAMU]

i just sprayed some belt conditioner on it and its a little better

ill do the bearins when i can

[Wacky Dee]

what makes you think it's realted to the water pump? I'm pretty sure I had the water pump replaced at the 100k service.

How much would alternator belt bearings cost? I'm still not sure it IS the bearings though, because from what I've been told previously if the bearings were shot they'd squeal all the time, not just on cold startup.

[blind_elk]

The tensioner bearing is for the timing belt. There is no tensioner bearing for the fan belt. The fan belt runs alternator / water pump / crank pulley / alternator - no tensioner bearing.

The screeching is probably due to a pulley being slightly out of alignment with the other 2. When you replaced the water pump, did all the pulleys line up? Are you sure you used the correct pump?

There is a spray you can get to prevent the screeching - check out any half decent auto shop.

[PUDZ 32R]

is the RB25 neo different from all the other RB engines?

cos the others run a tensioner to the aircon thats what i was referring to.

just try the stop squeak stuff but beware if the belt is slightly loose it will wlip and u wont be able to hear it.

[Wacky Dee]

the belt sprays don't last for long and need to be reapplied ... and as you said, they can mask the fact that the belt is still slipping and hence being damaged.

this is totally starting to shit me ... does anyone know where to get a belt tension guage PLEEEEASE? I have the manufacturer specs for how tight the belts should be so the only safe way to further tighten the alt belt is to check my current tension with a guage

[DAS KAMU]

i read it the alernator loading upon start up

[Wacky Dee]

what do you mean ? like an alternator overload at startupd due to some fault making the belt spin too fast and cause slipping?

[money pit]

If the spray on no-slip-stuff quietens the noise then its the belt thats the problem. Are you 100% sure that its the correct belt and that its correctly tensioned, these 2 things are the cause of 99% of belt screech. Any mechanic either professional or backyard should just be able to put their hand in there and say straight off whether or not the belt is tight enough.

If it was bearing noise then it wouldn't get better with the spray plus bearings make a noise all of their own, harsh metalic whining type sound.

The alternator can't make the belt spin faster, engine revs determine belt speed.

[blind_elk]

Just read the initial post again. If it is only happening on cold starts, it might be possible that the alternator bearings or water pump bearings need a shot of lubricant. When everything warms up, they are ok, so you don't get the belt screaming.

[Wacky Dee]

If the spray on no-slip-stuff quietens the noise then its the belt thats the problem. Are you 100% sure that its the correct belt and that its correctly tensioned, these 2 things are the cause of 99% of belt screech. Any mechanic either professional or backyard should just be able to put their hand in there and say straight off whether or not the belt is tight enough.

If it was bearing noise then it wouldn't get better with the spray plus bearings make a noise all of their own, harsh metalic whining type sound.

The alternator can't make the belt spin faster, engine revs determine belt speed.

the new belts are all genuine Nissan ones .. cost me an extra $100 even though I paid for the original ones and labour, but anyway..

The belt tension seems fine ie. tight as it should be (its def not too loose) ...and the whole 'any mechanic would know' is a load of bollox imo. There's so many young apprentices who wouldn't think twice about overtightening the belt just to get the belts to stop screeching (I know because previous belts were tightened way too much by a young local mechanic when the whole screeching started.... $20 3 min job, I guess you can't expect much more).

The only real way I will ever be sure about the tension is if I can find someone with a belt tension/deflection guage. I have the Nissan spec sheet so all I need is the guage but no one seems to have it.

On the topic of belt speed / revs - that kinda explains it then. When the engine is cold completely and I start it, it hits 1500 rpm at idle (and drops off to 900 in the next 2-3 mins) so this might be why it only screeches when its completely cold and only at startup.

I just need a tension guage now to confirm wtf is my tension and if I can go any tighter ... I have the guage part # so I'm just gonna call nissan and see how much it is. Sick of this shit and everyone (not you guys, the mechanics) not getting it right.

Edited December 17, 2008 by Delta Force

[skylinekid]

seriously mate just tighten it up not so its aguitar string and very tight..... i use to have issues with throwing powersteer belts if the car ever touched rev limiter... i would go through 4-5 belts a week.... yes im heavy on the limiter lol... but the only fix was over tighten it and i hadnt never threw a belt ever again. u wont really hurt the alternator aslong as u dont do it up extremely tight... short of that check the grooves of the pullers for shit stuck in there if so clean them out with a screw driver...

[Wacky Dee]

just a quick question ... if I overtighten the fan belt and there's eventually damage to the bearings, what sort of $$$ would I be looking at to get the bearings fixed/replaced?

[money pit]

Because the noise shuts up when the choke goes off (idle revs drop) then I reckon without doubt that the belt is not tight enough. Obviously this is without being able to see it in person.

The only rule of thumb technique I've heard of is to twist the belt (on the longest run) through 90 degrees. You should be able to just get it to 90 without straining yourself, anymore than 90 and its not tight enough. If it still squeals after you've done this then just nip the tensioner bolt a turn or two until it stops screeching when you fire it up.

Like Skylinekid says, unless you tighten it like a guitar string then its highly unlikely you'll do any damage to any bearings.

The reason I asked about the "correct belt" wasn't to find out which brand you used but just to check that it is the correct one i.e. genuine nissan doesn't necessarily guarantee that its the right belt for that particular application. Theres literally hundreds of belts which have only very slight variations in them.

After you've got this problem sorted then I reckon you'll realise that being able to hand check the tension of a fan belt is not bollocks.

Agree though that its pretty piss poor if you've paid some-one to check it and they still can't get it right. Good luck.