mx5cartalk.com

which flavour of mx5 do you own?

my NA8 has the same problem - sounds terrible on high rpm lift off, and when compression braking in hilly areas.

one solution may be to remove all the exhaust shielding? some of my shields look beaten up, especially around the cat.

Its quite likely that it may not be the exausts. Although it may be the heat shields arround them, check them by giving them a bit of a wack and see if they make the noise.

Its more likely that it is related to the gearbox. Its quite a common issue with the 1.6's, mine does it and so has every other one i've dríven. Basically it has a lot to do with the position and design of the gearbox. I've personally learnt to live with it, while it is annoying I guess it just adds to the character of the car.

Heres a link to some 'light' reading on the subject http://forum.miata.net/vb/showthread.ph ... ge=2&pp=25

I'm currently of the opinion that it may be the throw out bearing which is causing it, it seems that its one of the only possible fixes not covered by this thread. Some people found success in changing the 1.6 diff for a 1.8 diff, but for others it was un-successful. Some one on here found it to be caused by wear in the gearbox casing where the shift rods sit.

Hope this has helped.

Ben

Yes agree with loose heat shields and the gearbox/diff noise....but there is also another known issue with the early exhausts.

If you follow the exhaust header down to where it joins the exhaust pipe before the cat you will see that the pipe has a heat shield around it. It is held on by spot welding. On eary exhausts one of those spots welds breaks and in the rev range you mentioned the heat shield vibrates against the exhaust pipe. There are 3 ways to fix this.

1. Bend the heat shield away from the exhause pipe

2. Put a hose clamp around the heat shield and tighten it to stop the vibration

3. Replace the header with after market extractors, most of these extend from the engine to the cat and eliminate the faulty heat shield.

Hope this helps

By the way one of the reason why replacing the 1.6l diff with one from a later model elimates the noise is that the later models have a stiff rubber isolation plate where the drive shaft mounts to the diff. This absorbes some of the backlash when lifting off the throttle. It worked for me.

J

have you checked the rubber exhaust hangers? It is likely they have deteriorated and the exhaust is just hanging by the metal hooks.

Maybe a baffle in the cat converter has broken off?

yeah sorry for the month later input but the heat shield will be the problem

I had exact same prob on mine i tried to weld sections of the shield back on cause it was embarrassing coasting up to lights and have that raspy vibration noise goin on every time the car did like 3000 rpm

here is a picture of what we are talkin bout and see the points were i tried to bodge it




and yeah juffas right the best fix is a set of stainless extractors (you can see mine in the top of the photo
sorry if the piccys big all but it better illustrates the prob
cheers

Fixing a similar problem on my car... another example of an NA6 exhaust shield that has broken off from the welds:

Very Japanese, i assume there was a guy with a paintbrush on the production line who went around putting little dabs of paint over the welds.