NB belt squeal

[lobster940]

Hi - 1999 MX-5 NB 1.8 here.

I have a squealing noise from under the engine which starts after a minute or two of driving (it's cold out there!) - invariably when I brake to come to a halt at a junction etc. Squealing noise begins just before I stop. It will stop when I move off - hard to replicate exactly how to make it stop, but this morning it was when I switched the headlights off (and on again). Yesterday it was when I did a couple of sudden steering movements.

I am guessing, with the headlights, it's a perished/slipping alternator belt, or the alternator pulley. Any more ideas?

For the avoidance of doubt...the squeal does not begin the moment I start the engine. It is also only intermittent.

Many thanks!

[TVRees]

It's easy to tighten the belt. Give it a try.

[lobster940]

I'm guessing that a loose belt is already past it - it must have loosened itself somehow and got perished in the process - and I'm best off, for the sake of a tenner, just putting a new one on?

Is there a specification for how tight the aux belt should be - or do you just do it by feel? From some Googling there appears to be an adjustment rod/mechanism?

(Or is it blaringly obvious and I'm over-complicating things - to tell the truth I haven't actually popped the bonnet to look at the belts?)

[TVRees]

Tighten it a little bit and see if it stops squealing. That is what I sucessfully did on mine.

Generally, find a free section of belt and see how much up/down movement it has. More than +/- 5mm and it should be tightened.

[georgeyboy12345]

I had this problem with the aux belt in my NB I owned around 10 years ago. My usage profile didn't help, as I was using it for lots of short journeys like the 1 mile trip to work when it was raining and I didn't want to walk, 3 mile trip to gym/supermarket, etc.

Ideally, you would replace the aux belt/alternator/battery

[audikentman]

Tighen the belt, its loose, if that cures it get a new belt and fit it they wear into the grooves of the pulleys then chuck the old 1 in the boot as a spare.

[jamieduff1981]

It'll possibly seize its alternator after a while - every NA and NB we've had in our extended family has had one seize. Squealing belts usually starts sometimes before. The alternator drags a bit, the belt squeals, gets hot, goes slack. You tighten the belt, it works for a bit then the alternator seizes some time later.