Belt squeal on startup

alanmc

Hi lads and lasses,

My car is a 2004 Nissan 350Z.

I've noticed, in the last week only, my engine generates quite a large belt squeal on start-up. It lasts for maybe 30 seconds. It doesn't happen immediately on startup, but about a minute after the car starts. Actually, it's probably when I'm moving off and the crank spins up.

Anyway, when the squealing happens, the battery guage drops to 12 volts. So I've narrowed it down to the Alternator belt (which runs the power steering and water pumps as well). I haven't been able to check if it's the alternator pulley sticking (i.e. bearing gone in it), or the belt is sticking itself. The belt seems to be in very good nick. It also seems quite tight. About 1/2 cm deflection between the top pulleys with my finger pressing it quite hard.

When the car is warmed up, there is no squealing at all. I've ordered a belt from Nissan. It should arrive on Friday so I'll swap it out at the weekend.

My question is: Is it possible that the fault lies in the alternator? Could it be sticking when cold but then miraculously work ok when warm? When I have the belt off, can I check the alternator pulley? What would I be looking for? The fact that it's only when cold would lead me to believe it's the belt.

Any input is graciously accepted.

Al.

itarumaa

When you change the belt, you can check all the pulleys. (When the belt is off)

Just try to turn the pulleys, if you can do it without much force then it is fine.

If they are really hard to turn, then you have a problem.

If you dont change the pulley in time (assuming there is a problem) then it might sieze and take the tensioner with it.

This kind of problem ended my driving with old Volvo S40.

alanmc

Good to know. I might even get at it this evening.

Thanks for your input.

alanmc

Right, so I haven't had a chance to take off teh belt yet. But .... since the weather has warmed up a little, it doesn't appear to be squealing anymore in the mornings.

Does the cold make the belt contract? Make it tighter? Or would it just affect the friction between it and the pulleys? I had a look at the pulley surfaces yesterday and they don't appear to be fouled with oil or water or anything even remotely foreign.

listermint

alanmc wrote: »

Right, so I haven't had a chance to take off teh belt yet. But .... since the weather has warmed up a little, it doesn't appear to be squealing anymore in the mornings.

Does the cold make the belt contract? Make it tighter? Or would it just affect the friction between it and the pulleys? I had a look at the pulley surfaces yesterday and they don't appear to be fouled with oil or water or anything even remotely foreign.

Cold alters near all materials in the engine compartment, Belts are no different. Between metal rubber, expanding and contracting you willl get all sorts of new sounds with the change in weather conditions.

alanmc

listermint wrote: »

Cold alters near all materials in the engine compartment, Belts are no different. Between metal rubber, expanding and contracting you willl get all sorts of new sounds with the change in weather conditions.

What I'm trying to get at is maybe the belt is a little too tight? This could be exacerbated by the cold weather.

I'm probably worrying unduly. I think I'l give it a few weeks and see what the story is then.

Thanks for your reply.

listermint

alanmc wrote: »

What I'm trying to get at is maybe the belt is a little too tight? This could be exacerbated by the cold weather.

I'm probably worrying unduly. I think I'l give it a few weeks and see what the story is then.

Thanks for your reply.

I wouldnt assume its too tight, we've had some record breaking weather of late, especially in the midlands.

Tails142

Yeah I had similar problem which was a pulley/tensioner seizing which eventually stopped squealing after I ignored it for a couple of weeks and then a couple of weeks later it disintegrated entirely and left me stranded at the side of the road.

So I wouldn't try the wait and see approach.

alanmc

Tails142 wrote: »

Yeah I had similar problem which was a pulley/tensioner seizing which eventually stopped squealing after I ignored it for a couple of weeks and then a couple of weeks later it disintegrated entirely and left me stranded at the side of the road.

So I wouldn't try the wait and see approach.

Ehhhhhhhhh .... right so. This weekend then, the belt is coming off.

itarumaa

I did the same thing with Volvo s40, I waited that maybe the noise would go away.

Yes it did, 4 days and 200km later when pulley seized, destroyed the tensioner and knocked out the belt leaving the car without charching and power steering.

Also there should not be any reason the belt to be too tight or loose, because the tensioner should always keep the belt in right setup.

And you cannot see the problem with the pulleys just watching them, you have to take the belt out and then test them, are they moving freely or not.

Inside the pulley there are bearings and if those go, the pulley will be seized and that will then usually break the tensioner.

I personally hate these new systems, old ones used before were way more simple and better.

alanmc

itarumaa wrote: »

Also there should not be any reason the belt to be too tight or loose, because the tensioner should always keep the belt in right setup.

And you cannot see the problem with the pulleys just watching them, you have to take the belt out and then test them, are they moving freely or not.

I may have this wrong. But on my car, the "tensioners" is manually adjusted. You undo the centre bolt and wind it in or out with an adjustment screw at the bottom. Is it sprung as well?

itarumaa

alanmc wrote: »

I may have this wrong. But on my car, the "pensioners" is manually adjusted. You undo the centre bolt and wind it in or out with an adjustment screw at the bottom. Is it sprung as well?

Ok, this might be the case, then since you have ordered the new belt, it might be best to change the belt, check the pulleys that they move freely, add the new belt and adjust that it is tight enough.

Then see if there is still any more noise left.

Nissan doctor

alanmc wrote: »

I may have this wrong. But on my car, the "tensioners" is manually adjusted. You undo the centre bolt and wind it in or out with an adjustment screw at the bottom. Is it sprung as well?

The belt tensioners on the Z are manually adjusted, no springs.

The belt may look ok but they can wear in different ways, the ribs of the belt may be worn and when cold they don't grip the pulleys properly.

Unless you have very high mileage, a 350z won't have any issue with the pulleys themselves.