What is this engine noise??

[grizz]

This morning Nicola went off to work and 5 minutes layer she was home, dumping the MX5 and taking her daily.

"Its making a noise" was all she said.

I have filmed a bit of the noise, any ideas and advice appreciated.

Its basically a squealing noise. Not a fanbelt though. And hard to identify where it came from.

It seemed to go away after 4-5 minutes.

[grumpy]

I'm no mechanic but it could be a cambelt tensioning pulley - i had this making a noise on a old golf gti . I only found out after it let the belt slip round ! Other than that it could be the more obvious stuff , alternator bearings /starter/aircon?

[cobblers]

Yeah that's a pulley of some sort. I don't recall these having an idler pulley on the alternator belt, so it's probably the cambelt tensioner. These aren't an interference engine so if the tensioner does totally collapse and spit the belt off, the engine will be OK.

[grizz]

Thanks guys.

Started it up this morning and like you guys say, lower revs has it whining, and gets quiet soon as car warmed up after 5 minutes.

If you pick up the revs by 200-300rpm from idle it has a whine that changes a bit as well.

Took the car put for a 25 mile drive once slightly warmed up and no noise.

I think the noise is coming from the alternator side as well.

Here is a clip I made this morning after start up. Engine still cold.



All was quiet once engine warmed a bit.

[Dez]

mx5s are known for alternator bearings being sh!t, ive fixed a few with this problem. take the belt off and see if the bearings in it seem ok or rough/noisy. its an easy 30 quid fix for a s/h alt if it is, and you can also check if its the water pump at the same time before you start dismantling to get the cambelt.