noisy front end

spikes · Postby **spikes** » Mon Aug 01, 2011 3:44 pm

only started the sound when you changed the timing belt or just recently?

the alternator belt should have 10mms of deflection, check that. another guess is the alternator bearing could be rooted

manga_blue · Postby **manga_blue** » Mon Aug 01, 2011 5:40 pm

The first question with an MX5, especially a while after a timing belt change, is does the front crankshaft pulley wobble a little?

If that's OK then you can start locating the noise a bit more precisely. A stethoscope can be very handy, even if it's just a steel rod onto the bottom of a plastic cup. Alternatively hold one end of a length of thin plastic hose to your ear and move the other (safely) around areas where you suspect the noise is coming from.

manga_blue · Postby **manga_blue** » Mon Aug 01, 2011 10:59 pm

'fraid so. The wobble is often an early symptom of the crank nose problem. I'd do some reading and then take it back to the workshop that did the timing belt change to discuss a proper diagnosis and a way forward.

Early MX5s, up to about '91, had what was called the "short nosed crank" or SNC. The nose at the front of the crank was not well enough designed to provide a strong mount for the crankshaft pulley. The crankshaft pulley is usually removed and re-fitted during a timing belt change. If the mechanic was sloppy or just unlucky in his work then some time later the pulley would start to work loose and wobble.

Mazda redesigned the crank nose for the later 1600s and for your NA8 - aka the "long nosed crank" or LNC. It's a fair bit better but still not perfect, so there are still instances of the problem on the LNC motors. The failure will turn up anytime from a few hundred kms up to thousands of kms after the timing belt job. On my NA8 it first appeared 40,000kms after the belt change and I didn't fix it (with a new crankshaft) until I had other engine problems after 75,000kms.

There's a lot of posts about diagnosing it and repairing it. Try googling "short nosed crank" on this site or on http://www.miata.net.

Basically you've got a sympton of it. So there's some probability that you've got the LNC problem. If that's the case and the belt was changed 8,000km ago then there's a strong probability that you have the problem because the belt change was not done well enough.

93_Clubman · Postby **93_Clubman** » Tue Aug 02, 2011 12:48 pm

Excellent post by NMX516 on SNC & LNC problem here:
viewtopic.php?f=29&t=41916

Very useful post by Alf on his experience of this issue:
viewtopic.php?f=29&t=41895

Clearly you need to follow-up on the wobbly crankshaft pulley, but suspect your original rattle/ ticking sound is HLA noise: viewtopic.php?f=29&t=41116

Many forumites have had excellent results using Nulon Lifter Free.

manga_blue · Postby **manga_blue** » Wed Aug 10, 2011 3:13 pm

Glad it all worked out. Basically there's a much better chance of success with repairing an NA8 than with the early NA6s.

We should have warned you though that diagnosis by forum, more often than not, is totally wrong and just leads people off on wild goose chases.

mitch_f1 · Postby **mitch_f1** » Wed Aug 22, 2012 10:41 pm

Sorry to dig up the old thread with such a silly question, but for how long will the water pump last once it gets noisy? Mine was replaced a couple of years back with a new item, and it's pretty noisy now. I won't be able to have the time to fix it until the end of september.