High pitched fanbelt noise that goes away

snshami · Postby **snshami** » Sat Jan 29, 2011 6:57 pm

Hi, whenever I start the MX-5 it makes a high pitched noise. It does it only for or two seconds and then goes away. I am pretty sure that the car has new belts installed around 10,000km ago. The seem tight. Would a small spray of WD40 help or is that a bad thing to do.

mazdatenfive · Postby **mazdatenfive** » Sat Jan 29, 2011 7:00 pm

It may be a dry bearing.

snshami · Postby **snshami** » Sat Jan 29, 2011 7:10 pm

Wouldn't a dry bearing get noisier and not go away. Is there any risk in using WD40 on the belt to try and eliminate the belt.

aviper4u · Postby **aviper4u** » Sat Jan 29, 2011 7:40 pm

sounds like a loose belt.......

changed my drive belts a few weeks back and squeal occurred when revving only with ac ON so maybe pop the bonnet up and do some testing.....

if you are certain they tight though I'm at a loss

snshami · Postby **snshami** » Sat Jan 29, 2011 7:56 pm

I am not certain they are tight. How much freeplay should there be.

Mr Morlock · Postby **Mr Morlock** » Sat Jan 29, 2011 8:20 pm

Buy a manual for all references- there is a Haynes for NA amongst others. The big no no is not to overtighten belts as that puts extra stress on bearings and the belt. The manual probably tells you what is the deflection at the mid point. If you spray soap and water on the belt it is not going to cause any contamination( WD40 is a lubricant and does not dry out readily) and will make it quiet albeit temporarily if that is the cause. The belt(s) may need replacement or merely tightening.

Garry · Postby **Garry** » Sat Jan 29, 2011 8:48 pm

Sounds like an incorrectly tensioned belt to me. If you are starting the car with the A/C off then it is more than likely the alternator belt. If you let it go to long then the belt will glaze and never grip properly but if you already have new belts then they should be OK after they are tightened.

You could use Mr M's soapy water trick to work out which belt it is.

aviper4u · Postby **aviper4u** » Sat Jan 29, 2011 10:36 pm

manual i have handy for a (NB8B) says;

Uploaded with ImageShack.us

try comparing the two belts as the deflection is very similar?

zossy1 · Postby **zossy1** » Mon Jan 31, 2011 9:33 pm

If you feel confident enough to do so, pull all your belts and check the feeling and operation of your accessories and idlers.

To answer what some others have said - yes, it is possible for the noise to be there and then go away if you have a buggered bearing somewhere. The bearings seize up after sitting overnight, then squeal on startup until they warm up a bit. This is the classic warning sign of an accessory or idler bearing on the way out.

If they all seem OK, install new belts and re-tension the lot.

If this doesn't solve the problem, you may have a timing belt idler on the way... this can be tested by starting the car cold without the accessory belts installed.