Crank pulley... How freaked out should I be?

Inksta · Postby **Inksta** » Thu Jul 14, 2011 10:27 pm

Okay so I'm going to get this looked at either way, but I'm strapped for time and it could be a week or two before I can take it in to a mechanic. My crank pulley looks a bit off balance. A bit wobbly. Fairly subtle, but definitely noticeable when you compare to other pulleys that are spinning smoothly.

It's a long nose (8 slots in the crank pulley) B6 with 140,000ks. Swapped in to my NA 20,000ks ago.

Should I be grandpa-ing it around? Should I prepare a 21 gun salute? Or is it Jackie Stewart time, and I should be revving the nuts off it? All the SNC stories got me spooked.

Also: can anyone recommend a mechanic in Adelaide who knows MX-5s? Preferably in the Hills?

I have some mechanical ability but I'm not too keen to mess around with this as it's important and unfamiliar and I don't have a service manual yet.

Postby **NitroDann** » Thu Jul 14, 2011 10:34 pm

No need to be. Grab a 21mm socket and make sure the crank bolt is tight as all get out and you should be good to go. If its loose PM tighten it and PM me, ill gice you proper detailed instructions on how to fix it permanantly, and its easy.

Dann

JBT · Postby **JBT** » Thu Jul 14, 2011 10:37 pm

Ooops.

BP engines are just as susceptible to the crankshaft keyway failure/abnormal wear problem as the B6 engines. I'd not be driving it until you can get a good look at the crank pulley and keyway.

Inksta · Postby **Inksta** » Thu Jul 14, 2011 10:52 pm

*slap forehead*

I meant B6, not sure why I wrote NB?!

Thanks for your tips. I have checked, and everything is tight.

Postby **NitroDann** » Thu Jul 14, 2011 11:08 pm

Sometimes the outer sleeve isnt 100% parallel with the inner sleeve, via the rubber damper. This is what can make them look like they are gonna fall off. Ive experienced that feeling before. -looks at crank pulley, runs to toolbox with heart in mouth-

Dann

Inksta · Postby **Inksta** » Thu Jul 14, 2011 11:17 pm

Heh, no worries. I need somebody like you in SA to take her to!

There's an old thread in which someone recommends Manta Automotive, but they're friggin miles away.

Postby **NitroDann** » Thu Jul 14, 2011 11:28 pm

Just PM me anytime ;)

Dann

samx5 · Postby **samx5** » Fri Jul 15, 2011 10:40 am

PM sent Inksta.

Inksta · Postby **Inksta** » Sat Jul 16, 2011 8:41 pm

Thanks guys

And wouldn't ya know it... I just needed to keep searching:

Miata.net has an article detailing exactly my problem.
http://www.miata.net/garage/LongNoseRepair/index.html

The process sounds pretty involved. At least I know exactly what needs doing, now.

Cheers!

JBT · Postby **JBT** » Sun Jul 17, 2011 7:10 am

Inksta wrote:Miata.net has an article detailing exactly my problem.
http://www.miata.net/garage/LongNoseRepair/index.html

That's the crankshaft keyway repair procedure - doesn't always work. Is your's actually damaged?

Inksta · Postby **Inksta** » Sun Jul 17, 2011 11:03 am

Hmm. This is what got my attention:

The large accessory belt pulley will eventually begin to wobble. That's a lot of mass wobbling around, and it wears out the pulley hub, hub keyway, and keyway in the crankshaft. The key eventually breaks.

Inksta · Postby **Inksta** » Mon Jan 02, 2012 8:43 pm

Alrighty!

I've been a busy beaver, haven't been on here for ages, but thought I'd update this thread.

A few days ago I noticed the harmonic balancer was wobbling more markedly, so I garaged the car and managed to get to the crank nose today (pulley was a total pig to get off... wanted to resort to blowtorch but 40° and windy... not good).

The good news is that the wear is minimal, maybe half a mm in the worst spots. I plan to replace what I can and loctite the rest.

I'd like some advice from someone with experience with the various noses and pulleys. I'll take some photos tomorrow.

My questions are basically:
1) The key that was in there was shorter than the total key way by about 6mm. That doesn't seem right - is it?
2) The crank bolt I got sent over from mx5mania looks identical to the one that was in there, but the head is a little taller. Am I cool to use it?

Ps the 5 was fun in winter.... absolutely awesome in summer!

Inksta · Postby **Inksta** » Wed Jan 04, 2012 1:12 am

Think I might be talking to myself here, but for anyone searching in the future, I found the answer to my first question, after an hour of trawling, here:
http://forum.miata.net/vb/archive/index ... 81188.html

Essentially, Mazda made the key shorter at some point, and it should be fine as a replacement for the older, longer, chamfered key.

And I believe the answer to my second question is that the 'wrong' crank bolt would be a different diameter, so I should be fine with the bolt I got, which is the same.

Fingers crossed she holds together!

Inksta · Postby **Inksta** » Mon Jan 16, 2012 12:42 am

Definitely talking to myself. For those playing at home though...

Performed loctite fix. Discovered minimal wear to the crankshaft. Replaced everything I could (timing pulley, belt, pulley boss, crank bolt, oil seal etc). Put it all back together aaannnddd.... It's still wobbling :cry:

but it's a lot better than it was.

Pretty sure the crank nose is just rounded enough from the wobbling pulley boss that it's beyond repair. So now I'll continue to drive it as long as I can and eventually replace the engine I guess.

Oh, and when I disassembled it all I discovered the key had been inserted backward. Between that and the various other issues I've had, I guess the guy who did the previous engine swap was in a hurry or didn't care