NC2.0 serpentine belt change

  1. My model of MX-5 is: 2008 NC 2.0

A couple of months ago I decided to change the serpentine belt, tensioner and idler as preventative maintenance before a long hot trip in the summer. I ordered up the parts (Gates parts from Autodoc) at a total cost of around £85 including delivery.

Life got in the way a bit, so I never got around to fitting them until yesterday. Been slightly dreading doing it, images of skint knuckles, impossible to fit belt, and generally wasting my time.

But… it turned out to be really easy.

Battery out
Battery case splits, and top half lifts out
Bottom half just rotated out the way (four 10mm bolts)
Then long wrench on the tensioner, twist clockwise to loosen the belt and lift the belt off the idler.
Ease tension on the tensioner and lift out the belt. Note the belt routing, or you will be googling later.
Idler comes out with one central bolt.
Tensioner comes out with two bolts.

And reassembly is the reverse of the above. No worry about setting the tension correctly, the tensioner is just a wheel on a spring. Total job is under an hour going nice and slow.

My car is 2008, with 86k on the clock. The belt looked pretty solid, no sign of cracking. The tensioner was obvioulsy not new, but span freely and I am sure would be fine had I left it. But the idler…, span freely, but was definitely a bit “rumbly” and was on the way out.

So did it need doing…? Possibly not; maybe could have waited until the idler was more obviously failing. But had the idler bearing collasped, pretty sure the first I would know about it would be a warning light saying the alternator was not charging. And while I was thinking about that, the water temperature would be going up and we all know how that ends. Maybe there is enough throw on the tensioner to keep things turning if the idler collapses, and the noise would alert you to the failure. Just don’t know, and hope I don’t need to worry about finding out now.

If I was thinking about doing this again, I would take off the belt, examine it, and check the idler and tensioner bearings without removing them. If all was OK I’d just put the old belt back on again. I would probably mark the belt with chalk so it could be put back on again the same way, just incase reversing the action on an old belt had any untoward effect. If I was not sure of any of the components, I would then buy the bits I needed. An extra 40 minutes work every other year maybe… but probably worth it.

1 Like

Generally on Gates products it shows you the route diagram on the packaging.